Diamond is a material of extremes. It is the hardest, thermally most conductive, highest in breakdown field, the greatest in atomic density, and now one may also add, a most stable in single-photon emission even at 300Khellip;etc. Despite the tremendous attention and publicity given to discoveries of new carbon forms such as C60, carbon nanotubes, and graphene, diamond and graphite have remained two most successfully exploited carbon phases in technologies and science to date. The chance discovery of crystalline diamond nanowires (Hsu, et al., Nano Lett. 10, 3272, 2010) represents a step forward in diamond research, and opens door to a broad range of applications: ultraviolet (UV) light detectors and emitters, radiation particle detectors, high-speed high-power transistors, ultrabright electron field-emissions, biochemical sensors, and now stable high-efficiency single-photon sources, etc. However, fabrication of long, growth of crystalline diamond nanowires has proven to be a low-probability event. The first report by Hsu et al showed that crystalline diamond nanowires can be grown in an atmospheric pressure CVD process. These diamond nanowires are straight, thin and long, and uniform in diameter (50-90 nm) over the length of tens of micrometers. However, more study is clearly needed to find the optimal growth conditions and growth mechanism. To this end, we have investigated the effect of various parameters on the growth of diamond nanowires. One key parameter is the catalyst size, which is expected in the theoretical framework of capillary pressure that is inversely proportional to the wire diameter. Surface charge is also cable of reducing the Gibbs free energy of the diamond phase substantially enough for nano diameter wires to favor the diamond phase over graphite. A third growth parameter is hydrogen. The relatively low temperature at which the diamond nanowires were grown does raise an obvious question of cracking energy for H2. Independent experiments have pointed to the possibility that nanocarbon particle surfaces are able to react with molecular hydrogen at relatively low temperature, a phenomenon not witnessed with larger diamond particles.

Microplasmas are electrical discharges where the critical dimensions are less than 1 mm. Microplasmas based around a hollow-cathode design are extremely efficient, and as their size decreases, their operational pressure increases. For discharge cavities with dimensions of order 100 µm, operation has been demonstrated at atmospheric pressure. Fabricating thousands of these microplasmas on a large area substrate produces microplasma arrays. Such arrays may have a variety of potential applications, including removing contaminants from air supplies in enclosed environments (submarines, spacecraft), as flat panel light sources especially of near monochromatic light, as large area UV sources, and as small scale flow reactors for chemical processing. Until now microplasma arrays have been fabricated using Si or metals. We shall now present the results from the world&’s first diamond microplasma discharge, operating at above atmospheric pressure in helium. Making the entire device electrodes and dielectric - out of doped and undoped diamond, respectively, allows easy fabrication and removes interface problems. The negative electron affinity of the H-terminated diamond surface also allows the device to strike at lower voltages than with other materials, whilst the robustness of diamond should increase device lifetime. Results from multiple devices, i.e. arrays will also be demonstrated. This presentation shall discuss the issues surrounding this potentially new and exciting technology.

A Bias Enhanced Nucleation-Bias Enhanced Growth (BEN-BEG) process was used to grow UNCD films with porous structure. In this process, the substrate is exposed first to hydrogen plasma, in a Microwave Plasma-Enhanced Chemical Vapor Deposition (MPCVD) system, while applying a negative voltage to the substrate to produce ion bombardment-induced etching of the native SiO2 surface layer. Subsequently, the substrate was exposed to H2-rich/CH4 or Ar-rich/CH4 plasmas, while biasing the substrate with a negative voltage with respect to the plasma. This process results in the acceleration of C+ and H+ ions towards the substrate surface and sub-plantation of C+ ions, forming a carbide layer, which provides nucleation for the growth of the UNCD films. In prior work performed by our group, BEN-BEG resulted in smooth and dense UNCD films when grown at about 800 C of substrate surface temperature. The work discussed here focused on producing several UNCD films at several substrate surface temperatures in the 200-900 C temperature range. IN the work discussed here, UNCD films produced in the 200-700 C temperature range and high bias condition exhibit a porous structure on a layer up to the film surface, as revealed by SEM and TEM imaging. Raman spectra indicate that the porous UNCD have similar Raman signature as those of smooth/dense UNCD films, with the grains showing the characteristic UNCD nanostructure with 2~5 nm diameter grains. Cross-sectional Scanning Electron Microscopy (SEM) revealed that the modified BEN-BEG process results in 50% porosity with 100~150 nm diameter clusters. It was observed that the porosity or density changed as a function of growth temperature. Studies of bias effect on the nanostructure will be discussed. The structure is under investigation using high-resolution transmission electron microscopy (HRTEM) to determine the nanostructure and the diamond-silicon interface. The growth mechanism responsible for the porous structure will be discussed. In conclusion, the new BEN-BEG process with controlled substrate temperature appears may produce porous UNCD layers. This novel nanostructure of diamond exhibits mutifunctionalities that can be utilized in a range of devices or system components, such as membranes or electrodes for water purification systems and new Li-ion batteries due to the high resistance of UNCD to chemical attack in harsh environments. This work was supported by US Department of Energy, Office of Science, Office of Basic Energy Sciences-Materials Science, including the use of the Electron Microscopy Center, under Contract No. DE-AC02-06CH11357, and by the Dragon Gate program from Taiwan, supporting two PhD students from NCKU doing research at Argonne National Laboratory within a joint collaboration agreement signed between ANL and NCKU in Tainan-Taiwan

Due to its outstanding properties, diamond is considered as an ideal material for mechanical and electric applications at high temperatures, voltages, radiation, etc. However, the realization of various devices depends on the methods of diamond patterning. It is known that femtosecond lasers exhibit extremely high precision and minimized thermal effect in material processing. In this study, a seed-free diamond pattern growth method was developed by patterning silicon substrates using a femtosecond laser before diamond deposition through laser-assisted combustion flame synthesis. The resolution of the diamond patterns reaches micro scales. The diamond nucleation density can reach 10³ mm^-2 without diamond seeding. Peak position, full width at half maximum (FWHM), and diamond quality parameter were calculated from Raman spectra. The mechanism of the seed-free diamond growth based on the femtosecond laser patterning was investigated. The influence of processed silicon wafer surface roughness on the diamond growth nucleation and phase purity was studied, indicating that the nucleation density is proportional to the surface roughness.

Nano crystalline diamond thin films offer applications in various fields, but the existing approaches are cumbersome and destructive. A major breakthrough has been achieved by our group in the direction of a non-destructive, scalable and economic process of nano crystalline diamond thin-film fabrication. Here we report the cheapest precursor for the growth of nano crystalline diamond in the form of paraffin wax (saturated hydrocarbon polymers). We show that diamond thin films can be fabricated on a copper support by using simple, everyday paraffin wax under reaction conditions of Hot Filament Chemical Vapor Deposition (HFCVD). Surprisingly, even the presence of any catalyst or seeding that has been conventionally used in the state of the art is not required. The process is a significant step towards cost-effective and non-cumbersome fabrication of nano crystalline diamond thin films for commercial production.

Micro Electrode Arrays (MEAs) are common electrophysiology tools enabling to probe the neuronal activity distributed over large populations of neurons or from embryonic organs. Specific MEAs can be also used to build neural prostheses or implants to compensate function losses due to lesions or degeneration of part of the Central Nervous System (CNS) such as for Parkinson disease treatment, or for cochlear or retinal implants. One critical problem encountered when using microelectrodes with tissues is the narrow potential window they offer before medium direct ionisation. This implies that high currents may degrade the electrodes and alter the tissue itself from fibrosis. Also, the progressive fouling of the electrode is an issue since it leads to the loss of sensitivity of the MEAs, and this is particularly crucial when cultures are probed during several weeks. This paper describes a new approach to process Boron Doped Diamond (B-NCD) to fabricate MEAs. Direct patterning of the MEA is made available from controlled selectively grown diamond on patterned structures. The active layers were produced either on glass or oxidised silicon from a SEKI 6500 reactor producing 4 inch wafers on which conventional lithographic steps were conducted. Several process approaches have been used successfully, with varying geometrical structures according to the technological route. For example, the active diamond layers can correspond to the growth side of the material or to the seeding side, with influence on the resulting assembly. Adapting the process to enable substrate transfer and lift off enables the possibility to fabricate flexible MEAs with diamond pixels embedded in a soft matrix. This constitutes a significant advance for implant fabrication and prototypes of flexible 64 pixels B-NCD MEAs were tested in vitro and in-vivo. Confocal microscopy studies enabled to visualise the interface between the implant and retinal cells without removing the sample from the tissues, and observations demonstrated the absence of gliosis. Therefore, this study supports that diamond-coated implants could provide biocompatible neuroprostheses for very focal neuronal stimulations.

Determining actual human exposure to heavy metals through on-site measurement of urine samples is crucial for clinical and epidemiology studies. A reliable, handheld field sensor is needed by health care specialists to facilitate public health monitoring as well as to aid research studies on personal exposure. Current analytical and electrochemical methods suffer from lengthy sample preparation times and the requirements for specialized staff and equipment. Moreover, these methods often fail to provide accurate results in the presence of an organic matrix such as urine or blood. Giner, Inc. has employed the use of a high-performance Boron-Doped Diamond (BDD) electrode combined with a highly sensitive and selective stripping voltammetry technique to develop an electrochemical sensor for real-time measurement of trace heavy metals in urine. For example, novel sample preparation methods as well as customized detection algorithms have been developed to accurately determine low levels of cadmium from a single 1.5 mL urine sample. With specially configured BDD ultramicroelectrode arrays, the performance of the sensing element is expanded to accurately measure concentrations of less than 1 part per billion (ppb) cadmium in a variety of human urine samples. Owing to the wide electrochemical polarization range and highly tailored surface chemistry of the BDD electrodes, sensitivity values of as high as 5 mu;A/ppb are obtained even in the presence of other metals such as sodium, potassium, lead, zinc and copper. While the intended application for this sensor is to measure cadmium concentrations in urine to assess personal exposure, Giner, Inc. is also exploring alternative applications for this technology such as water quality monitoring for surface and groundwater.

Living cell-solid state device interfacing is anticipated to be one of the key bio-electronic synergies of the 21st century, especially in the fields of smart sensing, bio-technology, communications and medicine. One of the most fascinating topics in this area is neuron interfacing - the coupling of electronic devices to neurons. It offers the possibility for future non-invasive long-term neural signal recording from multiple neurons within artificial or natural neural networks. This will enable better understanding of neuronal functions and of associated diseases. Thin film diamond is ideally positioned to become a material of choice for neuronal applications. It is robust, conductive when doped, and is capable of electrochemical detection of low quantities of organic compounds, due to its high signal to noise ratio. The aim here is to investigate the effects of different surface pre-treatments on the sensitivity and selectivity of diamond electrodes towards dopamine and ascorbic acid. Several approaches have been used to improve the efficiency of ascorbic acid oxidation on diamond, including: the use of cathodic potentials (small and large, i.e. -2V to -35V), carbon nanotubes, electro-polymers (acid chrome blue K, and Evans Blue), hydrogen plasma, and the deposition of gold nanoparticles. Of these modifiers, the use of cathodic potentials, gold nanoparticles and hydrogen plasma treatment demonstrate the most promise towards the aims of this work. All three modifiers catalyze the oxidation of ascorbic acid, thus increasing the sensitivity and selectivity for dopamine in its presence. The modifiers leading to the hydrogen-termination of diamond, show the most promise as a basis for a diamond-based neuro-electrochemical device.

In previous work we reported on a diamond-based DNA sensor where we monitored the chemical denaturation of DNA by employing electrochemical impedance spectroscopy [1]. In this contribution we focus on the heat-transfer resistance at interfaces as a novel, denaturation-based method to detect single-nucleotide polymorphisms in DNA [2]. We observed that a molecular brush of double stranded DNA grafted onto synthetic-diamond surfaces does not notably affect the heat-transfer resistance at the solid-to-liquid interface. In contrast to this, molecular brushes of single stranded DNA cause, surprisingly, a substantially higher heat-transfer resistance and behave like a thermally insulating layer. This effect can be utilized to identify ds-DNA melting temperatures via the switching from low- to high heat-transfer resistance. The melting temperatures identified with this method for different DNA duplexes (29 base pairs without and with built-in mutations) correlate nicely with data calculated by modelling. The method is fast, label-free (without the need for fluorescent or radioactive markers), allows for repetitive measurements, and can also be extended towards array formats. Reference measurements by confocal fluorescence microscopy and impedance spectroscopy confirm that the switching of heat-transfer resistance upon denaturation is indeed related to the thermal on-chip denaturation of DNA. Interestingly enough, Velizhanin et al. recently predicted thermal conductivities for individual ds-DNA fragments [3]. Considering the 29-mer fragments as stiff rods with a length of 10 nm and a nominal radius of 1.2 nm, this conductivity translates to roughly one third of the value we derived experimentally for the disordered, single-stranded state. Keywords: Nanocrystalline CVD diamond, heat-transfer resistance, DNA sensors. [1] B. van Grinsven, N. Vanden Bon, L. Grieten, M. Murib, S.D. Janssens, K. Haenen, E. Schneider, S. Ingebrandt, M.J. Schöning, V. Vermeeren, M. Ameloot, L. Michiels, R. Thoelen, W. De Ceuninck, and P. Wagner, Lab Chip, 2011, 11, 1656 - 1663. [2] B. van Grinsven, N. Vanden Bon, H. Strauven, L. Grieten, M. Murib, K.L. Jimenez Monroy, S.D. Janssens, K. Haenen, M.J. Schöning, V. Vermeeren, M. Ameloot, L. Michiels, R. Thoelen, W. De Ceuninck and P. Wagner, ACS Nano, 2012, 6, 2712 - 2721. [3] K.A. Velizhanin, C.C. Chien, Y. Dubi, and M. Zwolak, Phys. Rev. E, 2011, 83, art. no. 050906.

The DLC [Diamond-like Carbon (ta-C : tetrahedral amorphous carbon), 10 mm-square, 1 µm-thickness, 2 nm-arithmetic average roughness] exhibits unique properties such as high hardness, high heat resistance, low coefficient of friction, and so it is expected to have mechanical application. For example, it can be used micro-gear for medical MEMS. Therefore, the nanopatterning technique for the DLC is essential to the fabrication of functional micro- and nano- devices. We had already investigated the nanopatterning of chemical vapor deposited (CVD) diamond films in room-temperature curing nanoimprint lithography (RTC-NIL) using diamond molds. We found that the diamond molds has a lifetime about 100 times longer than that of silicon (Si) molds using a conventional NIL process. The diamond molds had been fabricated with electron cyclotron resonance (ECR) oxygen ion shower etching using polysiloxane [-R_2SiO-]n with the electron beam (EB) lithography technology that we developed. However, we found that we cannot fabricate gear patterned diamond molds because of sharpened on the top. To overcome this problem, we have proposed the use of glass-like carbon (GC), as mold material, which has excellent properties similar to those of the diamond. We have investigated the fabrication of DLC micro-gears by RTC-NIL using GC mold, as an application to the DLC-based medical MEMS. A polished GC [10 mm-square, 3.2 mm-thickness, 1.6 nm-arithmetic average roughness, Hitachi Chemical Co., Ltd., PXG-35] was used as a mold material. The polysiloxane [Hitachi Chemical Co., Ltd., HSG-R7-13] is sticky liquid at room temperature and exhibits stable negative-exposure characteristics in air. Therefore, the polysiloxane was used as EB resist and oxide mask material in EB lithography, and also used as RTC-imprint resist material. The DLC synthesized by filtered arc deposition method on Si substrate, which has excellent properties similar to diamond properties was used as a pattern material. We fabricated the GC mold that has gear patterns with minimum 6 µm-tip diameter and 500 nm-tooth thickness. We carried out the RTC-NIL process using the GC gear mold under the following optimum conditions: time from spin-coating to imprint of 1 min, imprinting pressure of 0.5 MPa and imprinting time of 5 min. Then the imprinted polysiloxane pattern on DLC was processed with an ECR oxygen ion shower apparatus [ELIONIX Co., Japan, EIS-200ER].However, we could not fabricate gear patterns in high accuracy because of the residual layer. Therefore we proposed removing process for residual layer with CHF_3 ion shower under the optimum conditions of 300 eV and 4 min. As a result, we succeeded to fabricate concave DLC gear patterns in high accuracy which has minimum 6 µm-pit diameter and 500 nm-tooth thickness.

The DLC (diamond-like carbon) exhibits unique electrical, mechanical, thermal, optical and chemical properties such as low dielectric material, high hardness, low coefficient of friction and high transmission, and so it is expected to have various applications. For example, it can be used emitter for flat panel display, micro-gear for MEMS and next generation patterned media. Therefore, the nanopatterning technique for a diamond is essential to the fabrication of functional diamond micro- and nano- devices. The room-temperature curing nanoimprint lithography (RTC-NIL) using polysiloxane [-R_2SiO-]n that we developed has certain advantages, including short steps, high throughput and low cost than conventional thermal-cycle NIL. We have already investigated the nanopatterning of diamond films in RTC-NIL, using glass-like carbon (GC) molds, which have been fabricated with electron cyclotron resonance (ECR) oxygen ion shower etching using polysiloxane in the electron beam (EB) lithography technology that we developed. However, we could not fabricate diamond nanopit arrays in high aspect ratio because the maximum etching selectivity of polysiloxane film against diamond film was as low as 4.7. To overcome this problem, we have proposed the use of aluminum, as mask material, which has resistance to oxygen ion shower etching. We have investigated the fabrication of DLC-dot arrays by room-temperature curing imprint-liftoff method using aluminum mask, as an application to the emitter. The DLC (10 mm-square, 1 µm-thickness, 2 nm-arithmetic average roughnesses, ta-C:Tetrahedral amorphous carbon, Si substrare) which has excellent properties similar to diamond properties was used as a pattern material. A polished GC (10 mm-square, 3.2 mm-thickness, 1.6 nm-arithmetic average roughness) was used as a mold material. The polysiloxane is in the state of sticky liquid at room temperature and stable in air exhibits a negative-exposure characteristics. Therefore, the polysiloxane was used EB resist and oxide mask material in EB lithography, and also used as RTC-imprint resist material. An aluminum was used as oxide metal mask material of liftoff. We have fabricated the GC mold of dot with 5 µm-diameter which have 500 nm-height. We carried out the room-temperature curing imprint-liftoff process using the GC mold under the following optimum imprint conditions, imprinting pressure of 0.5 MPa and imprinting time of 5 min. Aluminum film on the imprinted polysiloxane was prepared by vacuum evaporation method and its thickness is 100 nm. Finally, the polysiloxane patterns were removed with acetone and then aluminum mask patterns were fabricated. We found that the maximum etching selectivity of aluminum film against DLC was 35, which was obtained under an ion energy of 400 eV. Then we processed the patterned aluminum on the DLC with an ECR oxygen ion shower apparatus. We fabricated DLC-dot arrays with 5 µm-diameter and 1.5 µm-height with an aspect ratio of 0.3.

In recent years, organic light-emitting devices (OLEDs) have attracted much attention because of their excellent features. OLEDs are self-luminous and very thin because of their emission of light without backlight. Therefore, compared with liquid crystal panel, OLEDs have many advantages, such as low operating voltage, light weight, low power consumption, and fast response time. In addition, they are expected to be applied to ultra-precision medical instruments, electronic papers, and so on. We have fabricated the micro-OLEDs by room-temperature curing nanoimprint lithography (RTC-NIL) using a diamond mold. The OLEDs with applied voltage of 20 V emitted the light. However, we failed to obtain light of mold pattern formation because residual film occurred in the RTC-NIL process. To overcome this problem, we proposed the fabrication of micro-OLEDs by room-temperature curing nanocontact-print lithography (RTC-NCL) using DLC (diamond-like carbon) molds. The DLC (10 mm-square, 1 µm-thickness, 2 nm-arithmetic average roughnesses, ta-C:Tetrahedral amorphous carbon) synthesized by filtered arc deposition method on tungsten carbide-cobalt (WC-Co) substrate, which has excellent properties similar to diamond properties was used as a mold material. The DLC mold has been fabricated by electron cyclotron resonance (ECR) oxygen ion shower (ELIONIX Inc., Japan, EIS-200ER) with polysiloxane [-R_2SiO-]n (Hitachi Chemical Co., Ltd., Japan, HSG-R7-13) oxide mask in the electron beam (EB) lithography technology, and has life time about 100 times longer than that of silicon (Si) and silicon dioxide (SiO_2) molds using a conventional NIL process because diamond has many unique properties such as high thermal conductivity and low thermal expansion. We have fabricated DLC molds of micro-dot with 5 µm-diameter and width of 10 µm-pitch which have 500 nm-height. We fabricated the micro-OLEDs with RTC-NCL using DLC molds. Firstly, the DLC mold was spin-coated with PDMS (Polydimethylsiloxane), which was prepared main-component SIM-360 and curing agent CAT-360 (Shin-Etsu Chemical Co., Ltd, Japan) at a mass ration of 10 to 1, and mixed main component which was diluted twice with toluene and curing agent. The stirred PDMS has suitable viscosity and curable properties under room-temperature and its insulating layer is formed by RTC-NCL. Then, the DLC pattern was transferred to ITO glass substrate under the optimum contact-printing conditions. An ITO glass is used as anode. Finally, the patterned PDMS film is deposited with TPD (40 nm-thickness) [hole transport layer], Alq_3 (40 nm-thickness) [electron transport layer], and Al (200 nm-thickness) [cathode]. The fabrication and operation of micro-OLEDs in RTC-NCL using DLC molds were successfully demonstrated.

With the density of microelectronics devices increasing every year, there is a demand for the continued reduction of parasitic capacitance due to dielectric material in multilevel interconnections used for ULSI circuits. Recently, dielectric materials with a low dielectric constant value (low-k) were fabricated using various materials such as carbon nitride (CN_x) and nano-diamond [1,2]. The liquid phase synthesis of the CN_x films, has been attempted by using organic solution such as acrylonitrile [3]. The liquid phase synthesis offers numerous advantages over conventional vapor deposition techniques such as simple experimental apparatus, low synthesis temperature, and scalability of the synthesis area. Therefore, it is worthwhile to use the liquid phase synthesis to produce CN_x dielectric films. In this study, the composition, surface morphology, and electrical properties of CN_x films synthesized using acrylonitrile were examined. The experimental apparatus used for the synthesis consisted of a glass vessel, two Ti electrodes, a thermometer, and a DC power source. CN_x films were synthesized by applying a DC bias voltage to Si substrates immersed in acrylonitrile. The composition of the synthesized CN_x films was evaluated by XPS. The surface morphology of the synthesized CN_x films was observed using SEM. The MIS capacitors were fabricated by evaporating Al electrodes on the CN_x films, which acted as insulating layers. The dielectric constant k of each CN_x film was estimated by using the thickness of the film and the insulator capacitance obtained from capacitance-voltage (C-V) measurements. The XPS measurements revealed that the films synthesized in acrylonitrile was consisted of C, N, and O. The film density estimated from surface morphology of CN_x observing from SEM images depended largely on synthesis time. The resistivity of CN_x films was obtained as a value higher than 10¹¹ Omega;cm. From the capacitance-frequency (C-f) curves of the MIS capacitors, the capacitance was an almost constant value over a wide frequency range. The dielectric constant of CN_x films was revealed to indicate the decrease tendency with reduction of the film density. In this study, the dielectric constant estimated as the lowest film density of the CN_x was confirmed to possess the value lower than the carbon doped silicon oxide (SiOC) as general dielectric material. Acknowledgements: This work was supported in part by Grant-in-Aid for Scientific Research (C) 22560303 of Japan Society for the Promotion of Science (JSPS). The part of this work was supported on “A Subsidy for Activating Educational Institutions” by Tokai University. References: [1] M. Aono and S. Nitta: Diamond Relat. Mater. 11 (2002) 1219. [2] Z. L. Wang, J. J. Li, Z. H. Sun, Y. L. Li, Q. Luo, C. Z. Gu, and Z. Cui: Appl. Phys. Lett. 90 (2007) 133118. [3] M. Higashi, H. Kiyota, T. Kurosu, and M. Chiba: Jpn. J. Appl. Phys. 50 (2011) 061502.

Despite recent developments in phosphorus, nitrogen and sulfur-doped diamond, the production of n-type semiconducting diamond with good electronic properties remains elusive. Theoretical studies have predicted that interstitial lithium will act as a shallow donor and will enhanced the electrical properties of diamond. Unfortunately, experimental methods, such as implantation and diffusion, failed to incorporate Li into diamond as an electronically active dopant. This is due to the low solubility of Li, plus its high mobility in diamond which promotes the formation of unwanted Li clusters. It has been suggested that the Li diffusion can be prevented by simultaneously adding nitrogen together with Li, with the N acting as a trap to pin down the Li in the diamond lattice and reduce its mobility, while retaining its n-donor properties. To study this, we investigate the incorporation of Li and N while growing diamond thin films in a hot-filament Chemical Vapour Deposition system. Microcrystalline diamond films were grown using a mixture of methane/ammonia/hydrogen gases with tantalum as the filament. The Li was added by placing crystals of lithium nitride (Li3N) near to the substrate and allowing them to slowly evaporate and condense onto the film due to the heat of the filament. SIMS depth profiles showed that this process produced high levels of Li and N (0.1% dopant level) situated in the same region within the diamond film. The crystallinity and morphology of diamond crystal produced were confirmed using laser Raman spectrometry and secondary electron microscopy. Despite the high Li & N content of the films the facetted diamond morphology, growth rate and crystal size remained unchanged. Sandwich structures containing layers of undoped diamond interspersed with layers of Li/N-doped diamond were deposited to better control the uniformity of the dopants throughout the film. Dopant profiles plus electrical characterisation results will be presented for a variety of these multi-layered sandwich structures.

Fluorescent nanodiamond (FND) is a nanoscale diamond material containing a high density of negatively charged nitrogen-vacancy (NV-) centers as built-in fluorophores. It is promising for biolabeling and bioimaging applications due to its unique absence of photobleaching and chemical degradation. However, the material has not yet received widespread attention in biology and biomedicine, because of their low fluorescence intensity compared to organic dyes, fluorescent proteins, and quantum dots. This work explores the possibility of increasing the density of NV- in nanodiamonds using nitrogen-rich type Ib diamond crystallites. We found a substantial increase (more than 4-fold) in the fluorescence intensity for these nitrogen-rich FNDs prepared by 3-MeV H+ irradiation and subsequent annealing. To illustrate the applicability of such high-brightness FNDs, the particles were conjugated with bovine serum albumin (BSA) modified for hepatic targeting or conjugated with streptavidin by a polyethylene glycol (PEG) spacer to acquire targeting specificity. The target-specific labeling or uptake of the modified FNDs by HepG2, C7 and MCF-7 cells were investigated. We thus demonstrated in this work the potential and promising applications of these bright FND bioconjugates. We expect that the development of these techniques will bring the biolabeling and cell targeting studies to a new level.

Nowadays, electrode materials based on boron doped diamond (BDD) films is available in a variety of forms and at varying levels of doping, resulting in films with unique properties. Among the numerous areas of electrochemistry, the BDD films have been applied in electroanalysis and also used to waste water treatment. Concerning these applications, some reports have evidenced their use in eletroanalysis and removal of nitrate. The presence of excessive nitrate in water, particularly, because of the use of nitrogen based fertilizers, may cause dangerous ecological complications. In this respect, the control of this species in biosphere has received an increasing attention. The use of electrochemical methods in comparison to other existing methods for nitrate reduction is associated to the use of clean reagents. In an attempt to improve the selectivity and sensitivity of BDD increasing its diversity and application for analyzing nitrate, this study presents the viability for electrodepositing of Cu/Sn alloy nanoparticles. First, it is known that metallic nanoparticles modified electrodes may exhibit certain properties otherwise unobserved in the bulk or macro electrode. Second, the Cu was shown to be the most efficient electrocatalyst concerning the rate of the nitrate reduction. However the main by-products obtained in the reaction, such as nitrite and ammonia are more toxic than nitrate. Moreover, the main drawback to the use of a Cu modified BDD is the instability of the nanoparticles due to their low adhesion to the surface. One way to solve these drawbacks may be achieved from the deposition of a Cu alloy. In this study, the use of the Sn for obtaining Cu/Sn alloy nanoparticles is also associated to the synergetic effect for the electrocatalytic nitrate reduction. The electrochemical deposition of the Cu/Sn alloy was studied on BDD grown by chemical vapor deposition technique at 780oC and 7h. A gaseous mixture (99% vol. H2 and 1% vol. CH4) with a pressure of 50 Torr was used. The boron doping was obtained from H2 forced to pass through a bubbler containing B2O3 dissolved in CH3OH with a controlled B/C ratio. The electrochemical deposition of the Cu/Sn alloy on BDD was investigated by cyclic voltammetry and its electrochemical response was compared to the pure system of Cu and Sn using solutions containing 0.5 M H2SO4 with (a) 10mM Cu(II) + 10 mM Sn(II), (b) 10 mM Cu(II) and (c) 10 mM Sn(II), respectively. From the studies of the deposition and dissolution processes on BDD, the formation of a Cu/Sn alloy was evidenced, particularly, by analyzing the dissolution process, where a dissolution peak was verified at a more positive potential compared to the dissolution process of the Sn and Cu system studied, separately. The electrocatalytic reduction of nitrate using the Cu/Sn alloy nanoparticles modified BDD has proved to be promising due to the significant increase regarding the involved current for nitrate reduction compared to the unmodified BDD.

Supercapacitors are power devices that have extremely high charge/discharge rates, very high power delivery or uptake and longer cycle life. These features make them suitable for applications such as supplement to batteries or as batteries and industrial power management. However, their application is limited due to low specific energy density (<10 Wh/kg). The recent emergence of carbon activated materials has shown a great potential but to be considered as a standalone power system, the specific energy density needs to be increased to values comparable with that of NiCd batteries. Boron-doped ultrananocrystalline diamond (UNCD) offers the widest electrochemical potential window with excellent chemical, electrochemical and mechanical stability, very high voltage scan rates, nearly ideal cyclic voltammograms and nanoscale grain size permitting highly conformal and high surface area porous structures. Since energy density depends on voltage, the wide electrochemical potential window of UNCD could offer high specific energy density. Here we present the recent findings that demonstrate a great promise for porous UNCD based supercapacitors.

Nanocrystalline diamond (NCD) thin films and magnetic nanoparticles (MNPs) are promising materials in terms of biomedical and sensor applications, and bioelectronics with magneto-responsive features. In this contribution, we present a novel concept of a hybrid nanocomposite, constituted of a nanocrystalline diamond thin film incorporating magnetic nanoparticles (MNPs). The NCD@MNPs nanocomposites therefore combine functional properties of the both unique classes of materials. For the fabrication, the NCD deposition technique using a high frequency pulsed microwave linear antenna plasma enhanced CVD (MW LAPECVD), working with low pressure and low temperature has been employed. Initially, we seeded substrates by a spin-coating with a diluted colloid consisting of NCD and MNPs. The concentration of both the MNPs and the NCD was varied in order to obtain homogeneous seeding and different ratio of the NCD to MNPs in the final thin film. For the depositions, a gas mixture H2/CH4/CO2 and low temperatures about 300°C at high plasma densities was used. Morphology of the grown nanocomposites films was studied by Atomic Force Microscopy and Scanning Electron Microscopy. The phase composition and the nanoparticle sizes were probed by X-ray diffraction. The nature of the carbon phase has been also examined by the Raman spectroscopy. Magnetic properties of the samples were studied using a SQUID magnetometer. The results of the detailed characterization and investigation of magnetic properties will be presented. We will suggest the best preparation approach of the nanocomposite NCD@MNPs thin films.

Low-k insulating layer with a relative dielectric constant k < 2 has been required to reduce a signal delay, power consumption, and cross-talk interference that occur in multilevel interconnection of ultra large-scale integrated circuit (ULSI). Carbon nitride (CN_x) has great potential as a low-k material due to its high resistivity and low dielectric constant. While the CN_x films have been synthesized by using various deposition techniques, the liquid-phase deposition has been attempted as an alternative deposition technique using organic liquid electrolytes. Previously, we have reported that continuous and uniform CN_x films were deposited on Si wafers with dimensions of 20 x 40 mm² by applying a DC bias voltage up to 3 kV to the substrate immersed in acrylonitrile (CH₂CHCN) liquid. However, our deposition technique must be scalable to the film formation on large-scale substrate that is used to the current LSI manufacturing process. In this work, a large area deposition of low-k CN_x film has been carried out using improved apparatus and deposition parameters. In particular, we have attempted to reduce the bias voltage during the film deposition because power consumption is supposed to rise in proportion with increasing the deposition area. The CN_x film is electrochemically synthesized by applying a DC bias voltage to Si substrates that are mounted on both positive and negative electrodes with parallel plate configuration. To reduce the bias voltage, the distance between electrodes is adjusted to 2 mm by placing PTFE (polytetrafluoroethylene) spacers between them. Typical deposition parameters are a bias voltage of 200 - 600 V, a current density of 0.5 - 1.5 mA/cm², a liquid temperature of 60°C, and deposition periods of 10 - 80 min. In this setup, continuous and uniform CN_x films are deposited on Si substrates by application of bias voltage lower than 500 V. The growth rates of the deposited films are strongly dependent on the bias voltage applied to the substrate. The thickness of the CN_x film is well controllable with modifying the intensity of DC bias voltage. The CN_x films with the relative dielectric constant k < 2.4 were obtained by optimizing the deposition parameters such as the bias voltage and film thickness, indicating that the CN_x film deposited in liquid acrylonitrile is a promising low-k material. Applying the bias voltage of 400 V, the CN_x films can be deposited on the Si wafers up to 100 mm in diameter. The power consumed for the film deposition on 100 mm wafer is as low as 15 W. From these results, the power consumption required for the 400 mm wafer processing is estimated to be 235 W, suggesting that the large area deposition of low-k CN_x film is achieved by our liquid deposition system with reasonable energy cost.

Boron doped diamond (BDD) is a very promising material for high frequency and high power applications like Field Emission Transistors, Schottky diodes, electrochemical and aerospace applications. On the other hand, the production of nano and ultrananocrystalline diamond (BDND and BDUND) films may result in the electroative area increase due to the diamond grain size decrease promoting their analytical sensibility and selectivity increase [1-3]. In this work, we prepared boron-doped diamond films with different doping levels and different grain sizes. BDD films were deposited on silicon substrate in a hot filament assisted chemical vapor deposition (CVD) reactor. The microcrystalline films were grown at 800°C for 8 h and the pressure inside the reactor was kept at 40 Torr. Boron was obtained from H2 forced to pass through a bubbler containing B2O3 dissolved in methanol. This system permits the control the boron concentration using a flow controller for the gas inlet. The CH4 flow is kept at 3 sccm (standard cubic centimeter per minute), the H2 flow is 197 sccm, and B2O3/CH3OH/H2 flow are 35 sccm for all experiments. The dissolution of in the range 5000 at 30 000 ppm of B2O3 in methanol was necessary to cover the whole range of B/C ratios studied. Afterwards, the nano and ultrananocrystalline films were obtained varying the argon percentage compared to hydrogen in the gas mixture at 50, 60, 70, 80 and 85%, and grown at 650°C for 10 h at 30 Torr. BDD films were morphologically and structurally characterized using electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, infrared spectroscopy (FTIR), X-ray diffraction (XRD) and contact angle measurements. Tthe diffractograms of BDD, BDND and BDUND films clearly depicted the (111), (220), (311) diamond crystallographic peaks. The boron incorporation promoted a change in diamond structure where the (220) peak became preferential with the boron content increase and grain size decreases. Raman spectroscopy results show good quality diamond films with their defined peak centered at 1332 cm-1 without the 1500 cm-1 band presence attributed to graphite for microcrystalline. This behavior was changed for nano and ultananocrystalline films where the peaks attributed to transpolyacetilene were prominent at 1150 and 1470 cm-1. The increase of boron level led to the appearance of two new low-frequency broad bands around 500 and 1200 cm-1 due to the boron pairs and the boron incorporation in diamond lattice, respectively, in all films. BDND and BDUND showed FTIR bands such as carbonyl groups in 1700 cm-1 and B-C in 1290 cm-1. In addition, in the microcrystalline BDD films the FTIR shows only C-H bonds in 2850 cm-1 and 2920 cm-1 and boron carbon in 1290 cm-1 without the presence of oxygen and unsaturated species. Thus, the carbonyl grain boundaries.

The hexagonal diamond (H-diamond) is energetically unfavorable and is therefore observed much rarely than the familiar cubic phase diamond. In general, H-diamonds are formed in very small quantities by direct transformation of cubic diamond using extreme conditions of pressure and temperatures [1]. Since hexagonal diamond is so rare to form it is a technical challenge to grow the hexagonal diamond in substantial quantity. In addition, the availability of the hexagonal diamond in large quantity would enable us to study its physical properties. Here in, we report our studies towards the realization of large concentration of hexagonal diamond thin films on highly oriented pyrolytic graphite (HOPG) substrates using hot filament CVD (HFCVD) technique. Prior to the deposition, the HOPG substrates were cleaned with ethanol, then seeded with diamond nanoparticles and placed inside the HFCVD reactor. Methane and hydrogen were used as precursor gases and the set chamber pressure during the deposition was 10 Torr. Deposited films were characterized using field emission SEM and confocal Raman microscope. The SEM images and Raman spectrum (with deconvoluted peaks) confirmed the formation of hexagonal diamond film on the HOPG substrate. Average crystallite size of hexagonal diamond films is found to be 300 nm. Deconvoluted Raman spectrum shows three Raman modes with peaks located at 1324 cm^-1, corresponding to the A_1g mode and at 1192.7 cm^-1 and 1305.9 cm^-1, corresponding to the polytpes of H-diamond. Reference [1] H. He, T. Sekine and T. Kobayashi, Appl. Phys. Lett. 81 (2002) 610.

Diamond films exhibits excellent properties as high thermal conductivity and low electrical conductivity, due to phonon phenomena. Also, its strong valence bonds allow gap values up to 5.4 ev. When diamond films are exposed to beta radiation, some electrons pass from the valence to the conduction band, and other stayed trapped between both bands. If the diamond is heated after beta radiation, the trap electrons could be encountered with their respectively holes or positrons emitting light at different frequencies, this phenomenon is called Thermoluminescence TL. The goal in this work is the estimation of the kinetics parameters of the tramp or electrons trapping such as frequency and energy supposing the intensity are a dose and temperature function. The three parameters Weibull distribution is employed to determine the trap characteristic.

Materials with extremely high bulk modulus and high hardness are marked with short bond length, high coordinate number, and low ionicity. Diamond is such a material and it is an excellent wide-band gap semiconductor. The first successful synthesis of diamond was achieved using high pressure and high temperature (HPHT) method by General Electric in the 1960s. However, besides the high price, the diamond synthesized by the HPHT process is in the form of small particles, ranging from nanometers to a few millimeters, too small for large-scale production of Diamond devices and materials. In this study, we will demonstrate how silicon carbide can be used as a substrate for high quality epitaxial growth of diamond on SiC. We will discuss growth of both the C and Si faces of 6H and other polytypes of semi-insulating SiC. The system required for the growth involves a hot-filament chemical vapor deposition system in which the distance from the source can be varied. Its basic system configuration allows for excellent and repeatable uniform growth processes for diamond. The grown epi-layer were characterized by a variety of different methods including scanning electron microscopy (SEM), energy dispersive x - ray spectroscopy (EDS) and Raman spectroscopy. The motilities of the as grown layer are a high as 420 cm2/v-sec.

At present, the many studies have been carried out to use the semi-conductive diamond for industrial applications. It has been required to deposit the diamond thin-film with high quality crystalline on large area substrate. The hot-filament chemical vapor deposition (HFCVD) is one of the deposition methods on the large area substrate. On the other hand, the substrate of the large scale silicon (Si) is easily obtainable and inexpensive. Moreover, the Si is suitable material for the deposition of the diamond thin film. Due to the large misfit of the lattice constant between Si and diamond, it is usually difficult to grow the epitaxial diamond on the Si substrate. Therefore, it is need to insert the buffer layer materials having the lattice constant intermediate between Si and diamond. The silicon carbide (SiC) that is easily obtained by carbonization of Si surface is included as one of the candidate material. In this study, the char layer was formed on Si surface by using HFCVD equipment, and it was analyzed from the various perspectives. The filament was made of the tantrum wire having 0.3 mm in diameter with the curling into a coil shape. After that, the filament was carbonized by HFCVD equipment in advance. The Si substrate was set below the filament, and the substrate temperature was measured by thermocouple. Hydrogen gas (100 ccm) and acetone vapor (0.4 or 0.6 ccm) were introduced to the reaction chamber which was pre-evacuated, and then the pressure was maintained at 1300 Pa. Moreover, the reaction time of carbonization was set for 30 min. or 60 min. The dark areas on the surface of fabricated samples were found by the scanning electron microscopy (SEM) observations. Besides, from the cross sectional observations, the many voids with inverted pyramid shape were confirmed from undersurface of the dark areas. Upper sides of the voids were wrapped over with a thin layer which formed on Si surface. In a previous study, the SiC from the surface of the samples fabricated through a similar way were identified by the X-ray photoelectron spectroscopy (XPS) analysis [1]. Therefore, this thin layer was recognized as the char layer. Additionally, we also investigate the crystalline of this layer observed by the transmission electron microscopy (TEM). Reference: [1] K. Haruta, H. Kimura, T. Kurosu: Proc. Schl. Eng. Tokai Univ., 50 (2), (2010) 45.

Nitrogen-vacancy (NV) center in diamond is an emerging system for quantum-logic device and sensor applications. The key feature of the NV center is the ability of spin manipulation at room temperature. Work is ongoing on optimization of the sensitivity of NV diamond-based magnetometers. We apply a wide range of electron irradiation to generate the NV centers in nitrogen-rich diamond for creating best sensitivity. Two methods are used to characterize the NV centers. The NV0 and NV- concentrations in electron irradiated diamond are determined from optical spectra. Additionally, electron spin resonance (ESR) has also proven to be an effective method for probing the electron spin transition between |ms=±1> and |ms=0> states of the NV centers. The resonance frequency of the electron spin is determined by applying and sweeping microwaves at around 2.87 GHz. A study of ESR frequency shift and signal broadening and magnetometer sensitivity as a function of electron irradiation dose has been conducted. Through basic proof-of-concept experiments and analysis, the research presented herein is a demonstration of sensitivity and minimum detectable magnetic field tailoring required for future-generation high-sensitivity diamond magnetometry.

Graphene, a type of two-dimensional (2-D) sp2 carbon nanomaterials, has attracted tremendous interests in many different fields in recent years. Owing to its interesting physical and chemical properties, graphene has also shown promise in various directions of biomedicine. In the past few years, our group has explored the applications of graphene for potential cancer therapies. It was shown that functionalized nano-graphene could be used as effective multi-functional nano-carriers for the intracellular delivery of drugs, photosentizers and genes. Excellent in vivo cancer treatment efficacy in mouse tumor models was achieved by the graphene-based photothermal therapy. Nano-graphene coupled with other inorganic nanoparticles could further serve as a multi-funcitonal agent for imaging-guided cancer therapies. In the mean time, we have also investigated the in vivo behaviors of PEGylated graphene using the radiolabelling method. We found that PEGylated graphene could be excreted from mice by feces and urine, without rendering noticable toxicity to the treated animals. Our results collectively encourage the further exploration of graphene-based cancer theranostics. References: 1. K. Yang, L.L. Hu, X.X. Ma, S.Q. Ye, L. Cheng, X.Z. Shi, C.H. Li, Y.G. Li, Z. Liu, Adv. Mater. 2012, 24, 1868-1872 2. K. Yang, J.M. Wan, S. Zhang, B. Tian, Y.J. Zhang, Z. Liu, Biomaterials, 2012, 33, 2206-2214 3. B. Tian, C. Wang, S. Zhang, L.Z. Feng, Z. Liu, ACS Nano, 2011, 5, 7000-7009 4. L.Z. Feng, Z. Liu, Nanomedicine, 2011, 6, 317-324 (Invited Review) 5. K. Yang, J.M. Wan, S. Zhang, Y.J. Zhang, S.T. Lee, Z. Liu, ACS Nano, 2011, 5, 516-522 6. K. Yang, S. Zhang, G.X. Zhang, X.M. Sun, S.T. Lee, Z. Liu, Nano Lett. 2010, 10, 3318-3323 (Highlighted by Nature)

Fluorescence from NV-centers embedded in diamond lattice is extremely photostable and it finds vast field of applications in optical microscopy, intracellular particle tracking, high-resolution magnetometry, and quantum information applications. By decreasing the size of bulk diamond crystals to nanodimensions, many chemical features of the material, as well as the fluorescence properties, change. In the talk, selected problems connected with surface modification of nanosized diamond crystals, attachment of chemical sensing architectures to them and their colloidal stability will be addressed. Fluorescent nanodiamonds modified by proper functional structures will be shown as unique unbleachable nanoprobes for construction of future sensors useful in biological and medicinal applications.

In recent year, Fluorescent nanodiamond (FND) has attracted much attention for application in biological field, such as single nanoparticle tracking and in vivo imaging. The FND containing nitrogen-vacancy color centers as fluorophores, is a promising alternative to organic dyes, fluorescent proteins, and quantum dots as biomarkers or biolabeling. The FND is not cytotoxic and has a perfect photostability, showing neither photobleaching nor photoblinking behaviours.[1] It is an ideal nanoprobe for long-term tracking and imaging applications, both in vitro and in vivo. Far-field fluorescence microscopy allows noninvasive characterization of biological device in living cell with specific fluorescent labeling. The confocal microscopy is a popular imaging technique in biology but the spatial resolution was limited to about 200 nm in the visible. The super-resolution microscope, such as Stimulated emission depletion (STED) microscopy[2] has been demonstrated to overcome this limit. The STED beam inhibits the spontaneous emission by stimulated emission and confines the signal to subdiffraction-sized spot, increasing the optical resolution. Applied to the imaging of FNDs[3], the technique has allowed us to achieve a resolution down to ~40 nm, which is 5-fold below the diffraction limit and represents a new regime of obtainable all-physics-based resolution using conventional optics.[4] Here, we reported the surface of functionalized FNDs, and applied STED microscopy to the image of biolabeling with FNDs. However, the FNDs are worked on the specific binding with cell&’s membrane. The images of fluorescence are colocalization between antibody-dye and functionalized FNDs by confocal and STED microscopy. FNDs are going to be the best candidate biomarker on the field of biomedicine or nanotechnoloy. Reference [1] S-J Yu, M-W Kang, H-C Chang, K-M Chen, and Y-C Yu, J. Am. Chem. Soc., 9, 17605, (2005). [2] S. W. Hell, J. Wichmann, Opt. Lett., 19, 780, (1994). [3] K-Y Han, K. I. Willig, E. Rittweger, F. Jelezko, C. Eggeling, S. W. Hell, Nano. Lett., 9, 3323, (2009). [4] Y-K Tzeng, O. Faklaris, B-M Chang, Y K, J-H Hsu, H-C Chang, Angew. Chem. Int. Ed., 50, 2262, (2011).

Biomedical monitoring using fluorescent nanodiamonds (fND) as cellular marker require specific fND size, depending on the particular application. In this wrok we shod that fluorescence in fNDs depends not only on the number and type of the colour centres, it&’s related to the fND size effects. We concentrate on such size dependence of photoluminescence (PL) properties of fNDs including quantum size phenomena that can be chemically controlled [1]. We applied the developed fNDs to carry out single photon measurements originating from NV centres in fNDs in various cells such as IC21 cells and report on specific interaction of fND with cell environment, depending on their functionalization. Fractions of fNDs were separated by centrifugation, creating groups of 8-10 nm, 10-20 nm, 20-50 nm and 80-120 nm for liquid measurements. fNDs was functionalised with three types of surface termination (H, OH, F), techniques of preparation [2] prevented aggregation of ND in aqueous solution within all size ranges. Additionally we attached charged molecules or biomolecules the surface such as PEI of different molecular weight and interacted with si-RNA. Based on the strong size dependence of PL NV-/NV0 ratio could be precisely tuned. We model mathematically the NV-/NV0 luminescence and discuss luminescence stability of single particles as a function of their size. Finally we applied this system fro sensing of si-RNA in IC21 cells. [1] Petrakova at al , Adv.Func.Mater. (2012) [2] Kreuger at al, Adv.Func.Mater (2012)

Multi-color cathodoluminescence (CL) from color defects in functionalized nanodiamonds is a promising technique for correlative light-electron microscopy (CLEM), and could be used to image nanoscale biological structures and chemically active surfaces. In addition to the A-band defect and nitrogen-vacancy defect, the silicon-vacancy (SiV) defect in nanodiamonds is also an efficient emitter under electron beam excitation. This defect has at least three distinguishing properties which make it extremely suitable as a CL bio-marker for imaging applications: (a) SiV emission is in the near-infrared with a zero phonon line centered at 738 nm for the negatively charge state and 946 nm for the neutral charge state; (b) the SiV color center has a very narrow spectrum linewidth, ~5 nm at full width half maximum, which promotes a high signal to noise ratio and efficient filtering; (c) the decay time for the SiV defect is on the order of nanosecond which is superior to many other potential biomarkers (e.g. rare earth doped nanocrystals) and can improve image acquisition speed. In this presentation, we discuss in detail these three advantages. We also will show a robust method to generate a high density of SiVs into nanodiamond crystals. We will also show the results of a systematic study employing atomic force microscopy, transmission and scanning electron microscopy electron microscopy, photoluminescence and cathodoluminescence that demonstrate the capabilities of SiV defects as a putative CL bio-marker. Finally, we present our initial results on incorporation of nanodiamonds with SiV defects into biological samples to demonstrate tracking and sensing.

The nitrogen-vacancy (NV) color center in diamond is gaining significant interest for nanoscale sensing applications. The optical addressability of its magnetically sensitive spin states and the potential to coherently control these states at room temperature makes this system an exciting candidate for spin-based magnetometry. With a home-built optical tweezers apparatus, we have demonstrated three-dimensional position control of nanodiamonds in solution with simultaneous optical measurement of electron spin resonance (ESR) [1]. Accounting for the random dynamics of the trapped nanodiamonds, we model the ESR spectra observed in an externally applied magnetic field, and observe d.c. magnetometry in solution with a sensitivity of ~50 mu;T/radic;Hz at 500 mu;T. This technique enables the three-dimensional mapping of magnetic fields in solution and may provide a pathway for spin-based sensing in fluidic environments and biophysical systems, such as the interiors of living cells, that are inaccessible to existing scanning probe techniques. [1] V. R. Horowitz, B. J. Alemán, D. J. Christle, A. N. Cleland, and D. D. Awschalom, submitted (2012) arXiv:1206.1573 [cond-mat.mtrl-sci].

Diamond nanoparticles host a number of paramagnetic point defects and impurities —many of them adjacent to the surface — whose response to external stimuli could help probe the complex dynamics of the particle and its local, nanoscale environment. Here, we use optically-detected magnetic resonance in a Nitrogen-Vacancy (NV) center within an individual diamond nanocrystal to investigate the composition and spin dynamics of the particle-hosted spin bath. For the present sample — a ~45 nm diamond crystal — NV-assisted dark-spin spectroscopy reveals the presence of Nitrogen donors and a second, yet-unidentified class of paramagnetic centers. Both groups share a common spin lifetime considerably shorter than that observed for the NV spin, suggesting preferential localization of bath spins on the nanoparticle surface [1]. Using double spin resonance and dynamical decoupling, we demonstrate control of the combined NV center - spin bath dynamics, and attain NV coherence lifetimes comparable to those reported for bulk, Type Ib samples. We also show a first result of transferring the NV polarization to the environment spins using Hartman-Hahn cross polarization experiments [2]. Extensions based on the experiments presented herein hold promise for applications in nanoscale magnetic sensing, biomedical labeling, and imaging. [1] A. Laraoui, J.S. Hodges, C.A. Meriles, Nano Letters, in press. [2] A. Laraoui, C.A. Meriles, under preparation.

Ultrananocrystalline diamond (UNCD) nano-pillars have been synthesized by a bias-enhanced nucleation and bias-enhanced growth process by microwave plasma enhanced chemical vapor deposition in a gas mixture of methane and hydrogen. UNCD pillars are coated with silver by thermal evaporation, which after thermal annealing forms silver nanoparticles on the surfaces of UNCD nano-pillars for biosensor applications based on surface enhanced Raman scattering (SERS). With excellent chemical inertness, diamond nanopillars are re-usable after easy surface cleaning and re-deposition of silver nanoparticles. Nano-pillars provide a very high effective surface area for supporting silver nanoparticles and result in increased effective sensing surface and sensitivity. Detection of adenine by plasmonic coupling among silver nanoparticles in diamond-pillar supported SERS biosensor is demonstrated. This paper will report the process for the synthesis of UNCD nano-pillars and their unique electrical, photonic and structural properties. The performance of SERS based biosensors based on coated silver nanoparticles on UNCD nanopillars will be discussed.

Due to the relative ease of reducing its electron affinity (EA) barrier by use of suitable surface treatments, diamond is a fascinating material for electron emission applications. A significant amount of research has been devoted to investigate the effect of various types of surface terminations on the work function of diamond. However, the surface terminations studied to date yield significantly large values of work function, and high temperature operation to enhance the electron emission results in an adsorbent free diamond surface. Using AIMPRO code, we have examined different stoichiometry of transition metals (TMs) and oxygen on the diamond surface. We find that for a correct stoichiometry, oxides of TMs, particularly Ti and Zn, exhibit a large negative EA of around 3 eV and the binding energies per TM atom, in the presence of oxygen, are significantly higher than previously calculated for similar TMs adsorbed onto a clean surface, being -5.04, -0.62, 0.37 and -0.22 eV with respect to bulk reference state of Ti, Zn, Cu and Ni, respectively. This indicates that in addition to a large negative EA, transition metal oxides (TMOs) show strong adhesion to diamond, and hence, would offer better thermal stability in comparison to alternative surface terminations. The electronic band structures of TMO coated diamond surfaces are also investigated. All four systems exhibit large band-gaps, consistent with a heterostructure of two insulators. However, depending upon the chemical nature of the system, the band gap is either widened or reduced according to the band-alignment of diamond and the TMO. Based upon these energetic and electronic properties, we propose here that the use of ultra thin coatings of selected transition metal oxides, such as oxides of Cu, Ni, Zn and Ti, can offer a permanent solution to diamond-based thermionics.

Recently our group proposed a new approach to energy conversion through combined photo- and thermionic electron emission from low work function diamond surfaces on metallic substrates. The low effective work function is achieved through nitrogen doping and hydrogen termination, and efficient visible light photoemission was induced through light absorption in the metallic substrate and charge transfer to the diamond film. To enhance the efficiency of this process we are proposing to employ a silicon substrate which is has an indirect bandgap and is optimally matched to the solar spectrum. It has been proposed that photon enhanced thermionic emission (PETE) can also substantially contribute to the emission current and energy conversion efficiency. This work presents a spectroscopic study of electron emission from a multi-layer structure composed of a boron doped Si substrate (absorber) and a nitrogen-doped diamond film (emitter). The films have been illuminated with light from 320 nm to 600 nm by employing a Xe arc lamp and band pass filters, and the spectra of the emitted electrons have been recorded as a function of temperature from ambient to ~360°C. TEM imaging has been employed to investigate the diamond-Si interfaces. The results show that engineering this interface can have a substantial effect on the emission performance. Modeling results are also presented to establish the significance of the different emission mechanisms (thermionic emission, direct photoemission, or PETE). The results reveal possible applications in combined solar/thermal energy conversion devices. This research is supported by the Office of Naval Research.

Enhancing charge transfer from diamond emitters can improve performance of devices utilizing electron sources as employed in power communications and direct heat to electrical energy conversion. This can be realized by ionization of gaseous species at low work function diamond surfaces. We will discuss this phenomenon in terms of the affinity level of the gaseous species and the diamond properties including work function, donor levels, band bending and negative electron affinity (NEA). Our doped diamond films were prepared by plasma assisted chemical vapor deposition utilizing nitrogen or phosphorus as dopant source. Gaseous species for surface ionization were prepared by passing molecular hydrogen along a hot filament generating its atomic species with an electron affinity of 0.75 eV. Nitrogen doped diamond films with work functions ranging from ~1.3 eV to ~1.5 eV were characterized by thermionic electron emission in vacuum. Under atomic hydrogen at a pressure of 1 x 10^-4 Torr the emitter with a work function of ~1.3 eV enhanced the thermionic emission current by a factor of 5.2 at a temperature of 500 °C. For the surface with a higher work function of ~1.5 eV an emission enhancement factor of 2.7 was observed. Phosphorus doped diamond films with a work function of ~1.3 eV exhibited a more than 10 fold enhancement of the thermionic emission current. Charge transfer to the hydrogen requires energetic alignment of appropriate levels in the diamond as the gaseous species approaches the surface and their vacuum levels align. The degree of alignment also depends on the amount of band bending and the value of the NEA both typically in the order of 1 eV. Emission enhancement can then be attributed to tunneling from donor states to the affinity level of the hydrogen atom. The lower work function nitrogen doped film presents more congruent energy levels resulting in higher tunneling probability. For the phosphorus doped film, its shallow donors align even more closely with the hydrogen affinity level suggesting a more pronounced charge transfer as observed in the emission measurement. This research is supported by the Office of Naval Research.

Diamond is not only the king gemstone, but also a promising material in modern technology owing to unprecedented thermal conductivity, high charge carrier mobility and chemical inertness. Less known is that defects in diamond can be used for quantum information processing. Owing to their remarkable stability, colour centers in diamond have already found an application in quantum cryptography. Furthermore, it was shown that spin states associated with single nitrogen-vacancy defects can be detected optically. In this talk I will discuss recent progress regarding spin-based quantum information processing and atomic magnetometry using single electron and nuclear spins in diamond

We present a hybrid diamond-silver resonator structure that provides enhanced single photon emission and collection by color centers in diamond. Our initial hybrid structure consisted of etched diamond nanoposts with implanted nitrogen-vacancy (NV) centers on a bulk diamond sample embedded in a silver (Ag) film. The resulting resonators provide Purcell factors of roughly 6 for the enveloped NV centers. Single photon emission can be accessed through the bulk diamond crystal, but only about 5% of the emitted photons can be collected, due to losses to surface plasmons and total internal reflection at the diamond-air interface. To improve single photon collection, we have introduced grating structures, consisting of periodic grooves in the silver film around the aperture, to coherently scatter surface plasmons into the collection cone. Our simulations indicate a 5-fold increase in collection efficiency as well as directional emission with the addition of gratings. The plasmonic corrugations were realized by defining rings of flowable oxide (a negative electron beam resist) in a second electron beam lithography step on the diamond sample before Ag deposition. After capping with Ag, we observed increased single photon emission (as confirmed by second order autocorrelation measurements) by apertures surrounded by gratings accompanied by comparable Purcell factors, corresponding to enhancements in collection efficiency by factors of 2-3.

The nitrogen-vacancy (NV) center in diamond is a paramagnetic defect that has generated considerable recent interest for applications such as nanoscale magnetic and electric field sensing. Much of this interest is motivated by the long spin coherence times (T₂) observed for NV centers in bulk diamond, however many of the proposed applications also require that these coherent spins be positioned within a few nanometers of the diamond surface. We demonstrate the reproducible production of shallow, depth-controlled NV centers with long T₂ times using an in-situ nitrogen doping technique [1]. Using reduced growth rates of ~0.1 nm/min, a thin, ¹⁵N doped layer (1-2 nm) is created by the controlled introduction of nitrogen gas during plasma-enhanced chemical vapor deposition of single-crystal diamond. Vacancies are created ex-situ by electron irradiation and NV centers are formed in the doped layer during subsequent annealing. We performed electron spin resonance measurements to characterize the spin properties of single doped NV centers, identified through the hyperfine coupling between the electronic and ¹⁵N nuclear spins. We confirm the depth localization of the doped NV centers is better than ±6 nm through experiments probing the local hyperfine interactions for NV centers confined in an isotopically layered ¹³C/¹²C/¹³C structure. Finally, we characterized the spin coherence of doped NV centers in a series of samples with depths ranging from 5 nm to 100 nm, showing T₂ > 100 (500) mu;s at a depth of 5 (50) nm. The consistently long spin coherence observed in such shallow NV centers enables applications such as NV center-external spin coupling. [1] K. Ohno et al., submitted (2012).

Nitrogen is a dominant impurity in diamond. In type Ib diamonds it occurs mainly as a substitutional impurity (Ns or C centre) while in type Ia it is usually found in complexes such as pairs of neighbouring Ns defects labelled A centres, vacancy-nitrogen centres, as well as nitrogen interstitial defects. In natural diamonds which have been exposed to high temperatures for millennia, the main nitrogen defects are A centres and B centres which are VN4. The most obvious mechanism for nitrogen diffusion is an exchange of a nitrogen atom at a lattice site with one of its neighbouring carbon atoms. However, previous theoretical studies estimated barriers of 8 eV which rules out this mechanism. Thus, other mechanisms involving vacancies or interstitials which form mobile complexes with nitrogen must be considered. Besides their importance for quantum information processing, nitrogen-vacancy defects may be crucial agents for the diffusion and aggregation of nitrogen. Indeed Collins has argued that NV is formed in irradiated synthetic type Ib diamonds around 800 C when vacancies become mobile and anneals around 1500 C with the formation of A centres and VN2 defects. However, there is no direct evidence for the involvement of vacancies in the production of A centres. Here, we use Density Functional Theory (DFT) and the Local Density Approximation (LDA) as implemented in the AIMPRO code to explore the migration and dissociation energies of NV. Moreover we discuss the influence of pressure on the diffusion barrier. An NV defect can migrate by a partial dissociation process first investigated for the diffusion of dopants in Ge and Si. The vacancy first interchanges with one of its carbon neighbours and the nitrogen atom becomes a substitutional defect. A second jump then occurs which moves the vacancy further away from the nitrogen atom. The energy of this arrangement of atoms is higher than the first step because of a charge transfer from the substitutional N atom and the vacancy. The vacancy then moves to a third neighbour site away from nitrogen. In this position it is able to return to a different site neighbouring the N atom. To effect a diffusion jump the N atom must change place with one of the C atoms bordering the vacancy. We estimate the total diffusion barrier to be approximately 5 eV. Under hydrostatic pressure of 4.42 GPa, the migration barrier for the vacancy decreases as the pressure increases suggesting that the vacancy in diamond is more mobile under pressure. Using the migration barriers we can estimate the temperature where diffusion is likely to begin. We estimate that NV is expected to become mobile around 1600 C. This is somewhat higher than found in the studies by Pezzagna et al who found that the luminescence of NV0 when introduced by ion implantation disappeared around 1300-1500 C. This would correspond with a barrier 10% smaller than found here but such an error is typical of density functional theory.

The recombination properties of excitons bound to dopant impurities are of a particular interest to quantify donor [1] or acceptor [2] concentrations in diamond. Cathodoluminescence (CL) spectroscopy then contributes to an evaluation of the dopant electrical activity in different situations. First, in n-type homoepitaxial diamond, the phosphorus donor activity is shown to be strongly dependent on the (100), (111) or (110) crystalline surface orientation chosen for the diamond CVD growth. CL mappings of the donor concentration at the sub-micrometer scale further evidence the role of macrosteps produced by a growth on vicinal substrates [3]. In a second part, devoted to p-type diamond, we show that the formation of boron-hydrogen complexes leads to the passivation of boron acceptors [4]. Their unstability under electron beam at low temperature is demonstrated and the dissociation mechanism is discussed [5]. [1] J. Barjon, P. Desfonds, M. A. Pinault, T. Kociniewski, F. Jomard, and J. Chevallier, J. Appl. Phys. 101 (2007) 113701. [2] J. Barjon, T. Tillocher, N. Habka, O. Brinza, J. Achard, R. Issaoui, F. Silva, C. Mer, and P. Bergonzo, Phys. Rev. B 83 (2011) 073201. [3] M. A. Pinault-Thaury, T. Tillocher, D. Kobor, N. Habka, F. Jomard, J. Chevallier, and J. Barjon, J. Cryst. Growth, 335 (2011) 31. [4] J. Barjon, N. Habka, J. Chevallier, F. Jomard, E. Chikoidze, C. Mer-Calfati, J. C. Arnault, P. Bergonzo, A. Kumar, J. Pernot, and F. Omnes, Phys. Chem. Chem. Phys. 13 (2011) 11511. [5] N. Habka, J. Chevallier, and J. Barjon, Phys. Rev. B 81 (2010) 045207.

Diamond intrinsic properties make it a good candidate to achieve fast and high power applications. Nevertheless, n-type diamond doping is still an issue. δ-doping appears as an attractive alternative to realize electronic devices. Its basic principle relies on the delocalization of the numerous holes from a heavy doped and very thin sandwiched p+ layer ([B]> 5 1020 / cm3) to a highly conductive low doped p- layer [1]. The key issues concern the boron concentration control to achieve the metallic transition with very sharp p+/p- interfaces. First this study will focus on very sharp interfaces. This has been fulfilled by designing a new gas injection system installed on the CEA MPCVD diamond reactor. We come up with a new approach which consists of injecting the gas as close as possible to the substrate during the growth via a quartz tube [2]. According to SIMS measurements, a 2nm/decade upward and a 5nm/decade downward doping gradients have been achieved. Moreover, the doping level of the p+ layer was increased up to 5.1020 / cm3 while a low boron level of 1016 / cm3 was achieved for surrounding p- layers. These doping gradients and maximum boron concentration will be compared to a second approach develop in the NEEL institute which consists to inject a very high gas flow during the growth [3]. Then, material and electrical characterizations have been performed on the samples. CL measurements performed on p- samples indicate that no compensation occurs and confirm a good crystalline quality. The peak attributed to the defect band remains relatively weak compared to the excitonic ones. These low boron doped layers have been electrically characterized by Hall effect measurements at room temperature showing high carrier mobility values close to the state of art [4]. Highly reproducible δ-doped structures were grown using TMB with the above characteristics in a MPCVD type reactor. Additional electrical characterizations of the delta-doped multilayer stack have been performed on mesa structures defined by e-beam lithography. Indeed, the influence of diamond substrate quality (Ib and IIa) on the electronic properties will be discussed. References: [1] R.S. Balmer et al, Phil. Trans. R. Soc. A (2008) 366, 251-265 [2] P. N. Volpe et al, Diam. Relat. Mater. 22 (2012) 136-141. [3] A. Fiori et al, Diam. Relat. Mater. 24 (2012) 175-178. [4] P. N. Volpe et al, Phys. Status Solidi RRL 6 (2012) 59-61.

The low ionization rate at room-temperature of all dopants in diamond hampers the use of this material as a semiconductor. Mostly because of the resulting low on-state resistance, this feature severely limits the technological potential of diamond-based power or high frequency devices. Various types of homopolar devices have been proposed to circumvent this intrinsic shortcoming, among which delta-doped structures. But even in this case, despite two decades of efforts devoted to boron delta-doping, device performance remained way below the initial expectations. This failure has been recently attributed to the combination of the very low delta-doped region thickness (<2 nm) necessary for confinement effects in diamond and of the very high doping level required for the insulator to metal transition (well into the 1020 cm-3 range). This property is actually a consequence of the small Bohr radius of the acceptor level in this material, which is just another aspect of the high ionization energy. In order to test if such a basic feature of diamond was indeed the reason for the lack of success of previous attempts, we have developed various techniques to achieve buried metallic diamond layers in the nanometric thickness range. However, as our delta-doped layers grew thinner, we were faced with the limitations of classical characterization techniques such as SIMS. In this work, we show how Hall effect and conductivity measurements performed on mesa-etched structures over a wide temperature range allow to estimate the free carrier surface density (doping level x thickness) of such ultra-thin buried metallic layers. We describe also the fabrication of Schottky diodes on top of such delta-doped structures grown on a heavily doped diamond pseudo-substrate. These devices enable us to perform additional C(V) measurements. Doping profiles tentatively deduced from these two electrical methods are then compared to chemical composition profiles, as well as to the results of in situ and ex-situ optical measurements. The results allow us to restrict even further down the practical delta-doping thickness range where a significant mobility enhancement could possibly be observed in diamond.

p-type diamond doping with boron is nowadays well controlled over a wide range of concentrations. In the literature, two boron gas precursors were previously used to grow BDD films: diborane (B2H6) and trimethylboron-TMB (B(CH3)3. However, no comparison of both precursors was at the present time reported using the same CVD reactor. The present study focuses on the boron incorporation and doping efficiency for each precursor in the same metallic CVD reactor. According to our results, the boron incorporation is higher with diborane using the same B/C ratio compared to TMB. Nevertheless, our SIMS and Cathodoluminescence results suggest that the metallic transition ([B] > 5 1020 / cm3) could be reached whatever the precursor. Using optimized CVD conditions, boron concentrations up to 2 1021 / cm3 were even measured with TMB. These results constitute a significant progress. Indeed, a [B] saturation below 5 1020 / cm3 was previously observed by other groups using TMB [1, 2]. Moreover, Hall measurements carried out at 300 K emphasized the high crystalline quality of p- diamond layers grown with TMB [3]. Measured mobilities were comparable to those reported for BDD grown with diborane (1250 cm2/Vs) [4]. References [1] V. Mortet, M. Daenen, T. Teraji, A. Lazea, V. Vorlicek, J. D'Haen, K. Haenen, M. D'Olieslaeger, Diam. Rel. Mat. 17 (2008). 1330-1334. [2] T. Teraji, H. Wada, M. Yamamoto, K. Arima, T. Ito, Diam. Relat. Mater. 15 (2006) 602. [3] P. N. Volpe, J. C. Arnault, N. Tranchant, G. Chicot, J. Pernot, F. Jomard, P. Bergonzo, Diam. Relat. Mater. 22 (2012) 136. [4] J. Pernot, P.N. Volpe, P. Muret, F. Omn`es, V. Mortet, K. Haenen, T. Teraji, Phys. Rev. B 81 (2010) 205203.

Heavily boron-doped diamond has been widely used as electrode for electrochemical and biochemical applications due to its unique chemical and physical properties. In this talk, we will summarize recent activities at Fraunofer IAF with respect to diamond electrochemistry and diamond bio-interface. In the first part of the talk, electrochemical realization/variation of different diamond surface terminations will be introduced. Based on this technique, the achievement of direct electron transfer process of redox proteins such as cytochrome c on diamond will be discussed. As new aspects, diamond electrochemistry in ionic liquid and catalytic reactions on metal (Ni, Cu, Pt) nanoparticles coated diamond electrode will be introduced in the last part of the talk. As examples, hydrogen evolution reaction and catalytic reduction of carbon dioxide will be shown.

Recent interest in renewable energy and the catalytic generation of chemical fuels is leading to increased emphasis on the fabrication of materials and interfaces capable of catalyzing reactions such as water oxidation and CO₂ reduction. These functions can be performed using homogeneous molecular catalysts such as Ru coordination complexes and porphyrins combined with chemical oxidizing/reducing agents, but linking these molecular catalysts to solid electrodes able to withstand the harsh conditions of catalysis (often highly acid and/or basic conditions) to achieve electrocatalysis has been difficult. Here, we report investigations characterizing the electrochemical activity, stability, and catalytic activity of molecular coordination complexes and porphyrins covalently linked to conductive diamond electrodes. By photochemically grafting terminal -OH groups to diamond followed by subsequent modification to produce azide-modified surfaces, we enable the Cu(I)-catalyzed azide-alkyne cycloaddition reaction (a form of "click" chemistry) as a highly versatile and modular way to covalently electroactive molecules to diamond surfaces. For example, akyne-modified Ru coordination complexes tethered to diamond can withstand more than 1 million oxidation and reduction cycles to potentials >+1.3 V. vs. the Normal Hydrogen Electrode with only minimal degradation, significantly exceeding the potentials needed for water oxidation. By modifying a cobalt porphyrin with pendant alkyne groups, we have succeeded in making porphyrin-modified diamond surfaces that exhibit facile electrocatalytic reduction of CO₂, with an onset at ~ -1.55 V vs. Ag/AgCl and exhibiting a turnover rate of 0.8 s-1 for 16 hours at a potential of -1.8 V. These results highlight the versatility of diamond as a nearly ideal support for "smart" electrocatalytic interfaces.

We report on the performance of a membrane electrode assembly (MEA) prepared using a high surface area (>100 m^2/g), electrically conducting (>0.5 S/cm) diamond electrocatalyst support. The support was prepared by overcoating inexpensive diamond grit with a layer of boron-doped ultrananocrystalline diamond (B-UNCD). A Pt loading of 0.5 mg/cm^2 was employed. Comparison studies were performed with Pt-loaded Vulcan XC-72. A 200-h accelerated degradation test was performed to assess the support stability. The diamond support provided superior performance compared to Pt-loaded Vulcan. During testing, a 40% loss in the Pt active area (ECSA) was found for Vulcan while only a 19% loss was seen for diamond. The open circuit cell voltage was similar for the two supports, 0.96-0.98 V vs. RHE, and was relatively stable during the test period. The ohmic resistance of the Vulcan MEA increased by a factor of 4 during the test period, while the resistance of the diamond MEA remain unchanged. Finally, SEM investigation of the MEAs after degradation testing revealed significant carbon loss and thinning at the cathode. In contrast, no thinning or carbon loss was seen for the diamond MEA. There was, however, some evidence of membrane detachment from the diamond surface. Taken together, the results indicate that the diamond support offers superior dimensionally stability and corrosion resistance as compared to commonly used Vuncan XC-72.

Photonic crystal (PhC) based structures are promising candidates for the realization of integrated, label-free optical biosensors [1,2]. Unlike silicon, that was used for most of these demonstrations, diamond offers a high stability and a versatile carbon surface that can be functionalized to covalently bond specific organic or bio molecules on its surface [3]. Here, we demonstrate the fabrication of a slotted PhC cavity in diamond with quality factors up to 1800 allowing the detection of refractive index changes induced at the diamond surface. Slotted cavities in two-dimensional PhCs realized from a local width modulation of a slotted line defect are known to provide high quality factors Q in silicon PhC cavities with modal volume V smaller than 0,05 (lambda;/n)3 [2,4]. We simulated slotted PhC cavities in diamond using a design similar to the one described in Ref. 4 that consists of a narrow slot of 100 nm in a width-modulated line defect in a PhC slab. Using finite difference in time domain (3D FDTD) simulations, we show that Q factors exceeding 1 million can be achieved while the modal volume can be smaller than 0.1(lambda;/n)3. This high Q/V ratio allows greatly enhanced light-matter interaction and make them promising structures for quantum information processing [5] as well as for biosensors since slotted PhCs confine light strongly in the slot, i.e. in the medium of low refractive index, near the surface of the diamond. The fabricated PhCs are etched in 360-nm thick polycrystalline diamond films and have a lattice constant of 610 nm, a hole radius of 145 nm and a slot width of 130 nm. To precisely inject light in a fully plane geometry, ridge waveguides suspended by nano-tethers and ended by inverted tapers are added at the end of the photonic crystal. Experimental transmission spectra clearly show the presence of a cavity mode in the diamond PhC at wavelengths near 1600 nm. The measured quality factor is 1800, a value only twenty times lower than the one achieved in silicon for similar structures and among the highest Q factor reported on diamond PhC [6]. As a proof of principle, we coated the sample with three nanometers of poly(diallyldimethylammonium chloride), a layer exhibiting a refractive index of 1.375. After coating, the resonance of the cavity mode is shifted by 1 nm towards the longer wavelengths showing a clear evidence of the detection by the structure of the refractive index change induced by the thin coating. These results open the road to the detection of more specific bio-chemical species taking advantage of diamond surface chemistry versatility. 1. E. Chow et al., Opt. Lett. 29(10) pp. 1093-1095 (2004) 2. M.G. Scullion et al., Biosensors and Bioelectronics 27, pp 101- 105 (2011) 3. C. Agnès et al., IOP Conf. Ser.: Mater. Sci. Eng. 16 012001 (2010) 4. J. Gao et al., Appl. Phys. Lett. 96, 051123 (2010) 5. M. P. Hiscocks et al., Opt. Express 17, p 7295 (2009) 6. J. Riedrich-Möller, et al., Nature Nanotech. 7, pp 69-74 (2012)

P. Gluche1, M. Wiora1, N. Wiora2, K. Brühne2, D. Zhu2, A. Sommer2 and H.-J. Fecht2,3 1Gesellschaft für Diamantprodukte GFDmbH, 89081 Ulm, Germany 2University Ulm, Institute of Micro and Nanomaterials, 89081 Ulm, Germany 3California Institute of Technology, Pasadena 91125, USA Nanocrystalline diamond (NCD) layers combine the remarkable properties of conventional diamond, such as extreme hardness and high fracture toughness with controlled and low intrinsic stresses, minimum surface roughness (few nm) and a low coefficient of friction (ca. 0.01). We report on the correlation between grain size (typically about 10 nm) and the relevant properties of phase pure NCD and N-doped layers. After a controlled seeding/nucleation procedure thick layers of NCD have been grown on single crystalline Si wafers up to six inches in diameter by hot-filament CVD. Based upon a sophisticated combination of photolithographic techniques and efficient plasma etching processes complex shaped microparts can be designed and produced from NCD layers. The Si-substrate can be chemically removed and free standing films or MEMS microparts with a thickness in the range of typically 10-20 micrometers can be fabricated on a reliable basis. First results using the piezoelectric effect of highly doped NCD point to potential applications for sensing devices. Furthermore, the surfaces of NCD can be chemically tuned by plasma processing with H-, O-, N- or Fl-termination resulting in sensitive and stable bio-interfaces with biomimetically designed topography. It is shown that in processes of cellular recognition and during first contact events, where cells decide upon survival or entering apoptosis, two parameters are crucial: (i) the biomimetic surface topography design and (ii) chemically tuned interfacial water layers in contact with the surface. These results open the gate to new ways in the design of biomaterials inspired by biomimetic principles.

We report on the optimisation of growth conditions for successful preparation of boron (B) doped nano-crystalline diamond (NCD) layers using microwave plasma enhanced linear chemical vapour deposition (MW PELCVD) apparatus [1] using H2/CH4/CO2 gas mixtures and trimethylboron as a dopant. We demonstrate deposition of B-NCD layers over large areas (up to 50cm x 30cm) using a range of substrate temperatures (Ts) from Ts < 400°C up to 700°C. Transparent B-NCD films have been prepared with a fixed B/C ratio of 5000ppm over a range of Ts. The incorporation rate of B into the solid phase has been studied. Raman spectroscopy, ellipsometry and atomic force microscopy (AFM) have been employed to investigate the quality of the prepared layers. Electrical and magneto transport measurements have been carried out to establish charge transport parameters. Cyclic voltammetry measurements have been performed to establish electro-chemistry characteristics. Nuclear depth profiling analysis measured the B-content in the layers. CO2 containing gas chemistries lead to high sp3/sp2 ratios ~98%, but the B incorporation decreases (by up to 2 orders) due to formation of BOx species in the gas phase. To improve B incorporation we show that plasma conditions are critical and can lead to high B doping with high sp3/sp2 ratios even without using CO2 chemistries. Our results on B incorporation are comparable with resonance cavity plasmas [2]. Raman spectroscopy confirmed the presence of high quality B-NCD with Fano related absorption at 1230cm-1. From the Drude contribution (from ellipsometry measurements) hole concentrations is studied at different Ts and compared with van der Pauw method. Nuclear reaction analysis confirmed [B] levels increase. We compare incorporation rates with earlier works [3] and conclude that a key factor in terms of the incorporation rate of B in H2/CH4/CO2 chemistries for B-NCD growth in MW PELCVD systems is growth temperature and plasma conditions Finally, we demonstrate a potential application of these B-NCD layers by demonstration of deposition of a B-NCD layer over a diameter of 15cm on a Si wafer with 5% uniformity of thickness and >1% uniformity of resistivity, together with cyclic voltammetry measurements showing promising electro-chemistry characteristics. 1. A Taylor et al: Diamond & Related Materials 20 (2011) 613-615 2. M Nesladek et al: Applied Physics Letters 88 (2006), 232111 3. W. Gajewski et al: Phys. Rev. B 79 (2009) 045206

Diamond has been traditionally be used in a variety of high temperature and high pressure applications due to its extreme mechanical and thermal properties. These properties are due to its well known sp3 tetrahedrally bonded lattice structure. Recent years have seen diamond as vital enabler of the nascent quantum information industry, serving as a host for single photon quantum emitters[1]. This has led to many attempts to process diamond to fabricate an all-diamond photonic device. For example, cavities have been fabricated to enhance the collection efficiency from single photons. The techniques used for making such structures typically involve ion implantation processes including lift-off and/or Focused Ion Beam milling. Many of these techniques rely on the formation of amorphous material. However, the amorphous material is associated with a degradation of the optical properties at the surface. To improve resulting photonic devices a clear understanding of the amorphisation route of diamond is needed. The breakdown of the lattice by ion implantation has traditionally been determined by the critical damage threshold, Dc calculated using Monte Carlo simulation packages such as SRIM. However such SRIM determined thresholds does not appear to accord well with the measured amorphisation thresholds Using a novel approach we show results obtained in Electron Energy Loss Spectroscopy (EELS) of light MeV implanted single-crystal diamond together with molecular dynamics simulations[2]. The combination of experiment and theory allows us to obtain a comprehensive understanding of how diamond amorphises under the implantation induced, and that strain is the driving mechanism for amorphisation, rather than defect driven as in the case for most crystalline solids. Weak-beam dark field (WBDF) images of the layer reveals a distorted diamond lattice between the undamaged diamond cap layer and the amorphous region. Using the WBDF transition point for Dc, we determine that DC is at 2.95+-0.10g/cm3. Molecular dynamics were performed whereby an initial diamond structure of different densities (2.0-3.4g/cm3) was obtained by either removal of atoms or stretching of the lattice. This structure was then annealed to obtain the lowest energy configuration. Analysis of the radial distribution function after annealing shows the breakdown occurs at 2.85+-0.10gm/cm3, in excellent agreement with experimental results. [1] I. Aharonovich, A. D. Greentree, and S. Prawer, Nat Photon 5, 397 (2011). [2] B. A. Fairchild et al., Adv. Mater. 24, 2024 (2012).

The p-type conduction, specific to diamond, obtained by hydrogenation of diamond surface has been applied to high-performance field-effect transistors [1]. This H-terminated surface needs to be passivated against oxidation. An AlN film is most promising for this purpose especially because of a potential to enhance the conductivity by a polarization. Conventionally, the AlN film was formed using MOCVD (Metal Organic Chemical Vapor Deposition) and the p-type conduction was obtained [2]. However, the conductivity was rather low partly because of an insufficient control of the film polarity. Therefore, we tried to resolve this problem using MBE (Molecular Beam Epitaxy) instead of MOCVD. After remote-plasma hydrogenation of a polished polycrystalline diamond substrate with (110)-preferred orientation, an AlN was deposited by MBE alternately supplying N radicals and Al atoms. Then, the sample was hydrogenated again, and the AlN film was removed in a chemical solution. The sample was electrically characterized after every afore-mentioned step using the van der Pauw method. The sheet resistivity Rs of the H-terminated diamond surface was originally 18kOmega;/sq. After the AlN deposition, Rs exceeded the upper limit (5 MOmega;/sq.) of measurement. This high Rs was caused by a loss of either terminating H and/or surface adsorbate. Considering that the conductivity was not recovered even after removing the AlN film which blocked the re-adsorption of the adsorbate, the high Rs might be due to the loss of the terminating H, caused by the exposure to the N radical during MBE. Therefore, through AlN filim we applied the hydrogenation to the system again, With AlN film, Rs has been recovered to 120 kOmega;/sq., which was only 7 times larger than the original value, indicating that the p-type conduction could be obtained under the AlN film. After removing the AlN film, Rs approximately returned to the original value. These results indicate that the H termination was almost completely recovered by the second hydrogenation through the AlN film. As to the adsorbate for the p-type conduction, one possibility was that new adsorbate was synthesized during MBE. Note that the original adsorbate formed by air exposure disappeared during the pre-heating of MBE. The other possibility was that the p-type conduction was induced by the polarization of the AlN film. We are now investigating which was the case and developing a method for enhancing the conductivity of the AlN/diamond system. We successfully achieved the p-type conduction in the MBE-grown-AlN/diamond heterostructue. Although the conductivity is presently one order of magnitude higher, this result proves the potential power of the MBE-grown AlN for AlN/diamond FET. Acknowledgement This study was supported by research grants from ALCA (JST). References [1] K. Hirama, H. Kawarada, et al., Apple Phys. Express 3, 1 (2010). [2] M. Imura, H. Amano, Y.Koide et al., Diam. Relat. Mater. 24, 206 (2012).

Layered dielectric films comprising of Diamond like Carbon (DLC) and Amorphous Fluorocarbon (a:C-F) were generated using three different stack configurations for ultra low dielectric constant (ULK) applications. These include a DLC - a:C-F - DLC sandwich, a:C-F - DLC topcoat only and an annealed a:C-F - DLC topcoat only film stack. These films were subsequently evaluated for thickness, dielectric constant, contact angle, surface roughness and chemical structure using IR analysis. Thermal stability was analyzed after annealing in Argon ambient at 400 C for 1 hour. Deposition conditions were optimized for film thickness, roughness, dielectric constant and contact angle using Minitab by tuning process pressure, substrate temperature and FRR. The modified Gaseous Electronics Conference (mGEC) reference cell was used to deposit DLC films using CH4 and Argon as precursors. Structural properties of the deposited thin film was studied using laser excitation of 633 nm in a Jobin Yvon Labram high-resolution micro-Raman spectrometer. Multiple points on each sample were analyzed in terms of the Disordered Carbon (D-peak) and Graphitic Carbon (G-peak). The thin film of DLC was subsequently annealed in Ar ambient for 1 hr at 400 C and analyzed. Commercially available graphing software was utilized to deconvolute peaks. The ratio of peak intensities as well as shift in their positions was determined to characterize the as-deposited and annealed film. The film was further characterized using AFM, FTIR, XRD, goniometry and electrical testing. Average film roughness as measured by AFM was less than 1 nm, the k-value was 2.5 and the contact angle with water was 42. A:C-F films were separately deposited using CF4 and Si2H6 (5% by volume in He) as precursors in a UNAXIS PECVD system. Films deposited using substrate temperatures between 120 C - 200 C, chamber pressure of 300 and 500 mTorr and power of 100 W were independently evaluated in terms of their electrical, physical, structural and optical properties prior to layering with DLC films. After process optimization, seven unique process conditions generated promising layered films with k-values between 1.69 and 1.95. Of these, only one film exhibited very low shrinkage rates acceptable for semiconductor device processing.

AlN/diamond heterostructure is applied to AlN/diamond n-p junction diode[1], AlGaN/GaN HEMT on diamond[2], AlN/diamond heterostructure FET[3] and so on. There are several reports of Metal Organic Chemical Vapor Deposition (MOCVD) growth[2-4], but it is difficult to observe the AlN growth on diamond in-situ during MOCVD. The growth mechanism has not been discussed intensively. In this study, we firstly report in-situ observation of AlN growth on diamond(111) surface by Molecular Beam Epitaxy (MBE) and discuss the growth mechanism. AlN film layer growth is controlled by alternative supply of Al atoms and N radicals from the upper part of growth chamber in order to mount a small diamond substrate (2x2mm) without additional holder which hinders the RHEED observation. During AlN deposition, we observed growth mode by RHEED in-situ,and evaluated AlN epitaxial orientation relationship by XRD pole figure and surface morphology by AFM. From in-situ RHEED obserbation at [2-1-1]direction of diamond(111) surface, the streak pattern indicating relatively flat growth appeared for the first time in AlN growth on diamond(111) and it changed the spotty pattern caused by island growth after 30 cycle deposition by MBE. A series of this pattern changes indicates Stranski-Krastanov growth. From XRD pole figure measurements of AlN 102 asymmetry reflection, single 6 fold rotational symmetry was observed in the AlN films, which have a single domain structure. In the RHEED observation, the diffraction pattern was changed from lattice rod distance a before deposition to lattice rod distance b immediately after the alternate Al and N supply. The reciprocal ratio of the pattern distance (1/a : 1/b=1 : 2.1) coincides with that of lattice interplanar distance of diamond (111) and AlN (0001) (adia/2:radic;3xaAlN /2=0.126:0.269=1:2.13) where adia and aAlN are the interatomic distance at coplanar of diamond (111) and AlN (0001), respectively. The pattern just after the Al and N supply is derived from AlN. This result supports that the hexagonal structure of AlN on atomic hexagon at coplanar of diamond(111) surface is rotated by 30°[4]. The lattice mismatch at AlN/diamond interface is 23.4% and 6.9 % for “no rotation” and ”30° rotation”, respectively. AlN grows mostly in “30° rotation” to seek less lattice mismatch condition[4]. In this study, we firstly observed the change from the diffraction pattern of hydrogen-terminated diamond surface to the streak pattern of AlN film clearly. Acknowledgement This study was supported by research grants from ALCA (JST). [1] C.E.Nebel, C.R.Miskys, M.Stutzmann et al., Diam. Relat. Mater. 12, 1873-1876 (2003) [2] K.Hirama, Y.Kasu et al., Appl. Phys. Lett. 98, 162112 (2011) [3] M.Imura, H.Amano et al., Phys. Status Solidi RRL 5, No. 3, 125-127 (2011) [4] G.Vogg, C.R.Miskys, M.Stutzmann et al., J. Appl. Phys. 96, 895-902 (2004)

Diamond is the preferred solid state material for producing thin (<5micron) membrane position sensitive detectors for low energy X-ray beam monitoring (XBPM): above the silicon K edge, diamond has about ten times higher X-ray transmission than silicon; diamond has effectively zero thermal leakage current; and correctly made diamond devices do not degrade under X-ray beam irradiation. Commercially available thin membranes (3-4 microns) are made of polycrystalline CVD (pcCVD) thin films. Due to the presence of grain boundaries in pcCVD diamond such detectors fail in terms of position measurement, when micro-beams are used or when single particle detection mode is involved. Here, for the first time, we propose to use the non-electronic grade (nitrogen content 5ppb<[N]<5ppm) single crystal CVD diamond as thin-membrane (1-10 microns) XBPM. Using deep Ar/O plasma etching it is possible to produce self-supported scCVD membranes (windows) of a size approaching initial size of the scCVD sample, with very good surface quality (no change in surface roughness after deep etch). After metallization and contacting, electrical properties of XBPM membranes were probed with 5.5MeV alpha-particles, synchrotron X-ray radiation and an ions micro-beam. scCVD membrane detectors exhibit: stable operation, charge collection efficiency close to 100%, with homogenous response, and extraordinary dielectric strength up to 30V/micron. Apart of detector applications such membranes can find their use in electron amplification, MEMS or photonics devices fabrication.

Diamond has attracted significant interest as a material for applications in devices working in extreme conditions. There has been increasing demand for diamond based electronic devices including high-flux beamline monitors. The typical preparation of these types of monitors involves oxygen termination of the diamond surface and subsequent metallization to provide blocking electrical contacts. Hard x-ray photoelectron spectroscopy (HAXPES) was applied to investigate the diamond-metal Schottky barrier height for several metals and diamond surface terminations. The position of the diamond valence-band maximum was determined by theoretically calculating the diamond density of states and applying cross section corrections. The diamond-platinum Schottky barrier height was lowered by 0.2eV after thermal annealing, indicating annealing may increase carrier injection in diamond devices leading to photoconductive gain. The platinum contacts on oxygen-terminated diamond was found to provide a higher Schottky barrier and therefore a better blocking contact than that of the silver contact in diamond-based electronic devices.

The superconductor to insulator transition goes on fascinating theoretical and experimental physicists alike. Reducing the dimensionality from 3D to 2D in order to induce a superconducting to insulator transition is a popular approach to this problem, and superconducting material systems are sought for where the control of the interfaces allows to reduce the thickness without affecting directly the electronic disorder. In this work we propose that heavily boron-doped diamond epilayers provide an original and promising playground to test such ideas. To this end, uncovered boron-doped diamond films were epitaxially grown on (100) oriented single-crystal diamond substrates by Microwawe Plasma-Enhenced Chemical Vapor Deposition in a NIRIM type reactor from a gas composed of 4% molar of CH4 in H2, with a diborane molar ratio of 24 ppm. We kept the same gas phase throughout a series of samples with thicknesses ranging from 1800 nm down to 20nm. A typical boron content was around 1% at., more precisely 1.5 10^21 cm-3 as measured by SIMS on the 600 nm thick film. Four point resistivity measurements were performed from 300K down to 0.1K. Over a comparable thickness range, we observed the same thickness dependence of Tc at similar concentrations as S. Kurihara et al.* on (111) oriented films : below 200 nm, the critical temperature increased with thickness by a comparable factor for both orientations, but over a different range of temperatures (1.5 K to 7.7 K for (111) films versus 0.5 K to 2.3 K in (100) films). Magnetotransport measurements were also carried out which yielded the Hc vs Tc phase diagram of the serie. The slope dHc2/dTc at low magnetic field observed on the 600 nm thick layer was -1.1 T/K as previously published by various groups, a value generally associated in such dirty type II superconductors to a coherence length of 10 to 30 nm. An original result of our study was that thicknesses below 50 nm, comparable to that coherence length, led to a much smaller slope, although the electronic disorder probed by transport and optical measurements in the normal state remained practically unaffected. A natural follow-up of these promising experiments was to perform similar measurements on buried superconducting epilayers. The preliminary results of such an approach will also be presented, yielding additional support to our premise that diamond provides an original and flexible platform for the study of superconducting to insulator transitions. *S. Kurihara et al., NDNC International Conference 2011, Matsue, Japan, Paper P4-12.

Diamond is promising as a substrate for power devices even from a viewpoint of a unique p-type conduction obtained by hydrogenating a diamond surface. We have previously developed field-effect transistors using this conduction [1]. The H-terminated surface needs passivation to block the influence from a surrounding environment. Previously, Kuech achieved this forming an Al2O3 film by an atomic layer deposition (ALD) method [2]. However, there was a concern about the reliability of their devices because the oxidant was H2O and the deposition temperature was relatively low (~100°C) in their ALD process. The purpose of this study is to investigate and enhance the reliability of the H-teminated surface optimizing the ALD condition. After hydrogenating a (001)-diamond substrate (Ib) in a hydrogen remote plasma, an 18-nm-thick Al2O3 film was deposited using ALD alternately supplying trimethylaluminum and oxidant (H2O or O3) at a temperature Tdep from 23 to 450°C. Some samples were further annealed in air at 550°C for an hour. The electric properties of the H-terminated surface with and without Al2O3 film were measured using the van der Pauw method. In the stage as deposited, the sheet resistivity Rs (10kOmega;/sq.) of the H-terminated surface markedly increased with Tdep beyond 150°C in the case of the O3 oxidant. By contrast, Rs for the H2O oxidant did not change for all Tdep&’s investigated (up to 450°C). Thus, H2O is more suitable for the oxidant in ALD. In order to examine the passivation capability, we applied a 550°C anneal in air, as an accelerated field test, to the Al2O3 film formed using H2O at 100°C or 450°C. Rs for the conventional 100°C deposition exceeded the upper limit (5MOmega;/sq.) of measurement after the anneal. It was still beyond the limit after removing the film. Because the adsorbate (a requisite for the conduction) was expected to re-adsorb on the diamond surface after the film removal, the H termination was lost by the high temperature anneal. The diamond surface was possibly oxidized either by oxygen diffusing inward from the air environment or by the reaction with the Al2O3 film. By contrast, Rs (9kOmega;/sq.) for the 450°C deposition did not change by the anneal. It is the first result of the p-type conduction of H-terminated diamond preserved at 550°C in air. Hence, we confirm that the Al2O3 film formed using the H2O oxidant at 450°C has an excellent passivation capability even in the case when it is as thin as 18 nm. To conclude, we succeeded in passivating the H-terminated diamond surface with a high reliability forming an ALD-Al2O3 film with an H2O oxidant at 450°C. This achievement leads to a stable operation of diamond power devices even at high temperatures above 300°C required for automobile applications. NB. This research was supported by grants from ALCA(JST). References [1]K. Hirama, et al., Tech. Dig.-Int. Electron Devices Meet., 2007, 873. [2]D. Kueck, et al., Diam. Relat. Mater. 16, 1306 (2009).

Diamond is a very promising material for high power, high temperature, high frequency electronic, and biotechnology applications. One of the limiting factors in the development of electronic grade boron doped diamond is the reliable determination of critical parameters such as the temperature dependent carrier concentration, mobility, and conductivity of the deposited diamond. Thus, a temperature dependent Hall Effect measurement system with software based data acquisition and control was built and tested. The sample stage is added to a commercially available cryostat and consists of an aluminum nitride plate on a custom designed heated copper stage. Electrical connection to the sample is made using 25µm gold wires connected to titanium and/or gold contacts on the sample that were deposited using physical vapor deposition (PVD). This presentation will describe the design details and system verification over the temperature range from room temperature to 700K under vacuum. Both van der Pauw and Hall bar geometries can be accommodated in this system as will be shown for various reference samples. Primary test samples include boron-doped single crystal diamond (SCD) films on high pressure high temperature SCD substrates deposited in a microwave plasma-assisted chemical vapor deposition (MPCVD) reactor [1]. Temperature dependent Hall effect measurements have shown carrier concentrations from below 10¹⁷cm^-3 to approximately 10²¹cm^-3 with mobilities ranging from 763 (cm²/V.s) to 0.15 (cm²/V.s) respectively. Further insight into the properties of these materials is gained through a single parabolic band model coupled to thermopower, electrical conductivity, and Hall effect measurements. References: [1] S. N. Demlow, I. Berkun, M. Becker, T. Hogan, T.A. Grotjohn. Dopant Uniformity and Concentration in Boron Doped Single Crystal Diamond Films, MRS Proceedings (2012) 1395, mrsf11-1395-n03-02 doi:10.1557/opl.2012.461

1. H-terminated diamond MOSFET with high temperature formed passivation layer Diamond is known as one of the wide-gap semiconductor and has many advantageous characteristics (high breakdown voltage, high-temperature operation capability, high thermal conductivity, etc.) when we fabricate many devices using diamond substrate. It also has a unique property that holes are accumulated densely on a hydrogen-terminated (H-terminated) surface. We have reported on field effect transistors (FETs) using this property [1]. Since the H-termination effect is unstable being affected by a surrounding environment (surface adsorbate, high temperature, etc.), it needs to be passivated. The hole accumulation layer is maintained when the Al2O3 film was formed on H-terminated surface using an atomic layer deposition (ALD) by trimethyle aluminum (TMA) and H2O as oxidant method at deposition temperatures of up to 450°C [2]. Even after an additional heat treatment at 550°C in air, H-termination didn&’t break and the surface p-type conduction was preserved. Based on the temperature stability, we tried to fabricate of metal-oxide-semiconductor field effect transistors (MOSFETs) using ALD Al2O3 film formed at 450°C that doesn&’t break hydrogen-termination by surface adsorbate and heating up at high temperature. 2. Expectation for higher temperature operation of H-terminated diamond FET The Al2O3 film serves as passivating layer and gate insulator in MOSFETs. H-terminated diamond MOSFETs using Al2O3 film is produced by the following 5 steps. First, deposition of undoped layer (500nm) on (100) single crystal diamond substrate. Second, evaporation of Ti/Au as source-drain electrode on undoped layer to form source and drain structure. Third, hydrogenation of undoped layer surface by remote plasma. Fourth, Al2O3 firm deposition by ALD method using H2O oxidant and deposition temperature of 450°C. Fifth, Al gate electrode deposition on Al2O3 gate insulator to form MOS structure. Since the Al2O3 film formed at 450°C by H2O has better insulation and passivation property than those formed at lower temperature, H-terminated diamond MOSFETs using the ALD Al2O3 will be operated in a better performance at higher temperature than ever reported in diamond FETs. [Acknowledgment] This research was supported by research grants from ALCA (JST). References [1] K. Hirama, H. Kawarada et al. : IEEE IEDM (2007) p.873. [2] A.Daicho, H.Kawarada et al. : JSAP abstract 18-F3-9 (2012).

P- and n-type doped diamonds underly the design of virtually all electronic and optoelectronic applications. To achieve such valency control, comprehensive knowledge of the fundamental processes that control impurity doping is required. For p-type, the impurity boron is easily incorporated into both natural and synthesis diamonds, whereas n-type diamond, which is not present in nature, has been recently established by phosphorus doping. Recent progresses in p- and n-type doping in diamond semiconductor have stimulated much research on the various types of p-n junction devices. Diamond has been identified as a potential candidate for use in high-power and high-frequency devices owing to its superior physical and electric properties. The highest breakdown voltage among wide-band-gap semiconductors with high thermal conductivity and high saturation velocity potentially lead to a higher attainable power density. Bipolar junction transistor (BJT) is one of the major power switching devices. BJTs may offer benefits in high-power applications, including potentially lower on-resistance from conductivity modulation due to minority carrier injection and the absence of a gate insulator reliability issues. According to the prospects of future BJTs based on several wide-band-gap semiconductors, it is expected that diamond BJT exhibits superior performance as a switching power device with high current amplification and low conduction loss. Quite recently, we have fabricated the prototype of diamond BJT with p-n-p junction structure on both (111) and (001)-oriented diamond by using the n-type phosphorus doped diamond, and the transistor actions with current gain properties of 10 can be obtained at room temperature operations. This observation of current amplification properties in diamond BJT is a major step that brings diamond closer to high-power switching applications. Detailed aspects of n-type doping for such diamond bipolar applications and the electrical properties of diamond BJTs will be discussed.

Despite experiments with sulphur and arsenic, the only viable n-type dopant for CVD diamond films to date is phosphorus. Literature shows many examples of successful homoepitaxial n-type doping achieved by several groups on (111) and (100) oriented substrates. However, incorporation of active phosphorus in (110) oriented substrates is still very difficult. This is due to a challenging control of stable growth on this surface. It was already shown on (110) textured microcrystalline diamond substrates that the grain orientation plays a crucial role, influencing the incorporation rate [1]. The application of similar conditions on single crystal substrates with different miscut angles have led to surprisingly high deposition rates of 20 to 50 mu;m/h. Although the incorporation of phosphorus was clearly proven, most of it is inactive due to an extremely high compensation ratio. To investigate the influence of substrate off-angle effects with respect to the (110) orientation, a set of phosphorous-doped (110) diamond films were prepared with 500 ppm of [PH₃]/[CH₄] in the gas phase, in combination with [CH₄]/[H₂] = 1 %, and p = 180 Torr. The commercial Ib (110) HPHT substrates from Sumitomo Electric Ltd. have been characterized by X-ray diffraction and electron back scattering diffraction to measure the off-angle of every individual substrate. To create clear distinct situations, primary focus was put on miscut angles of 0°, 5°, and 10°. Scanning electron microscopy and atomic force microscopy images revealed that the 5° substrate led to a relatively smooth film (R_a asymp; 12 nm) with the other samples showing higher roughness (R_a gE; 50 nm) due to the appearance of microfacets or nearly no growth at all. The substitutional nature of the phosphorus atom was confirmed by applying ultrasensitive photocurrent-based techniques technique. To rule out possible inhomogeneity in dopant incorporation due to structural defects at the sample edges, the transport properties such as carrier-concentration and mobility were collected using a Hall-bar geometry structured into the diamond film by a partial removal of the epitaxial diamond layer through the use of a metal mask and subsequent oxygen plasma etch. The results will be discussed with respect to the miscut angle and a comparison with the more established orientations of (100) and (111) will be presented. [1] K. Haenen, A. Lazea, J. Barjon, J. D&’Haen, N. Habka, T. Teraji, S. Koizumi, V. Mortet, J. Phys. Condens. Mat. 21/36 (2009), 364204. Financial support by the EU FP7 through Marie Curie ITN "MATCON" (PITN-GA-2009-238201) and the Collaborative Project ”DIAMANT” (No. 270197), and the Research Foundation Flanders (FWO) (G.0555.10N) is acknowledged.

Electrically conducting ultrananocrystalline diamond thin films are finding use in electroanalytical chemistry, field emission and as transducing platforms for chemical and biological sensing. These types of diamond films are grown from Ar-rich source gas mixtures. Boron-doping of these films strongly influences the electrical properties. The boron-doped, ultrananocrystalline diamond (B-UNCD) films are without a doubt “complex” in terms of their electrical properties. Several factors influence the electrical conductivity of the diamond films and the rate of charge transfer across the solid-liquid interface. For example, in electrochemistry, the diamond thin-film electrode response (i.e., electrode reaction kinetics) is controlled by the (i) potential-dependent density of electronic states, (ii) surface chemistry, (iii) morphology and microstructure, (iv) defect density, (v) nondiamond carbon impurity content and (vi) the doping level. The extent to which these factors affect the electrochemical response very much depends on the reaction mechanism for the particular redox system. This presentation will discuss the effects of the boron doping on the electrical, morphological and microstructural properties of B-UNCD thin films. Characterization data to be presented will include Hall measurements of the carrier concentration and mobility, boron nuclear reaction analysis to determine the boron-doping level, x-ray photoelectron spectroscopy to learn about the surface chemistry, Raman spectroscopy and NEXAFS to assess the local microstructure, and XRD to probe the film crystallinity.

Recently, in our join collaboration, we have demonstrated using B-doped NCD (BNCD) diamond for applications to photovoltaic as a replacement for ITO [1,2]. We have attached molecular wire D - A structures on BNCD films and compared their photovoltaic performance to D-A wired ton ITO electrodes. In this work, presented here we further develop this topic further by making a full photovoltaic structure solar cell using B-doped diamond as anode. The solar cell is composed from D-A : P3HT- PCBM photovoltaic medium wit a top Al contact. We measure the spectral dependence of the External Quantum Efficiency (EQE) and the photocurrent in wide energy range Based on the photocurrent measurements we can confirm a blue shift of the sub gap charge transfer related to photocurrent as well as enhanced response in the UV part of the spectra. The EQE measurements show that for obtaining the good performance solar cell the resistivity and transparency of BNCD layer is essential. Therefore we have used specific technology for preparation of high quality BCND, allowing how to reduce the Rs below 100 Ohms/ square while keeping transparency on ~75%. [1] Lim Candy Haley Yi at al ADVANCED FUNCTIONAL MATERIALS , 20, 1313-1318 , 2010 [2] Zhong Yu Lin; et al. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 17218, 2008

Nanocrystalline diamonds (NCD) are transparent in nature and exhibits electrical conductivity once doped with Boron. These NCD also inherits bulk&’s diamond toughness and high thermal conductivity characteristic. Such NCD properties give high potential in applications such as P-type transparent electrode that could revolutionize the improvements of touch panel and solar cell&’s devices, including for the usage in harsh conditions. Furthermore with the limiting resources of Indium in nature, which is one of the main materials for transparent electrode in indium tin oxide (ITO), give rise for the need to search for much better alternative and resourceful materials. Thus in this research, the possibility of utilizing Boron-doped NCD&’s electrical and optical transmittance is investigated and studied. High Boron-doped NCD with Boron concentration of above 1021 cm-3 was successfully grown on top of an undoped transparent NCD with quartz substrate by microwave plasma assisted chemical vapor deposition. The electrical property and optical transmittance characteristic of the deposited materials was investigated using Hall effect measurement and UV-visible spectrophotometer with light wavelength ranging from 300 to 800 nm respectively. The grown boron-doped NCD shows hole mobility values around 2 to 4 cm2 V-1s-1 which almost 10 times higher than those previously reported in conducting NCD. The sheet resistance was also measured to be between the values of 100 to 400 ohm/sq in the thickness less than 50nm. The transmittance value was detected to be within the range of 75 to 90% for the deposited Boron-doped NCD. These results had proven that high Boron-doped NCD could be considered as a promising candidate for the transparent electrode application. The mechanism on why such higher mobility values are possible is discussed and further investigation on the ways to increase mobility and maintaining high optical transmittance while reducing sheet resistance for the Boron-doped NCD is done. Since the optical transmittance of NCD would be affected as the Boron doping concentrations are increased, the optimum trade-off relationship between the electrical and optical properties of boron-doped NCD can be found. The substantial understanding of the origin of opaqueness due to Boron doping is also needed.