Symposium Organizers
Chia-Liang Cheng, National Dong Hwa University
David Moran, University of Glasgow
Robert Nemanich, Arizona State University
Greg M. Swain, Michigan State University
Symposium Support
Applied Diamond, Inc.
Cline Innovations, LLC
Element Six
Fine Abrasives Taiwan CO., LTD
Fraunhofer USA, Inc.
Microwave Enterprises, Ltd.
Plassys - Bestek
Seki Diamond Systems
R2: Electronic Devices and Applications
Session Chairs
Olga Shenderova
Daisuke Takeuchi
Monday PM, December 01, 2014
Hynes, Level 3, Room 303
2:30 AM - *R2.01
High Voltage DC Vacuum Power Switch Using Diamond PIN Junction Cathodes
Daisuke Takeuchi 1 4 5 Daisuke Kuwabara 1 3 5 Toshiharu Makino 1 4 5 Hiromitsu Kato 1 4 5 Masahiko Ogura 1 4 5 Satoshi Koizumi 2 4 5 Hiromichi Ohashi 1 4 5 Hideyo Okushi 1 4 5 Satoshi Yamasaki 1 3 5
1National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Japan2NIMS Tsukuba Japan3Univ. of Tsukuba Tsukuba Japan4ALCA(JST) Tsukuba Japan5CREST(JST) Tsukuba Japan
Show AbstractA vacuum power switch using diamond PIN junction cathodes have been developing, which make use of spontaneous electron emission through negative electron affinity (NEA) surfaces of hydrogen-terminated diamond. [1] Using unique properties of diamond such as NEA, carrier injection through the junction between band-conduction and hopping-conduction layers, and high-density free excitons as well as high thermal conductivity, 10kV d.c. switching has been achieved with the efficiency of 73% during room temperature operations.
Recently, the emission current density reached to 0.5 A/cm2, estimating with the PIN diode mesa area of 1.9 × 10-3 cm-2. High electron emission efficiency, which is determined by a ratio from the emission current to the PIN diode current, in the range of a few percent has already been obtained. According to the system model, it gives the practical efficiencies of more than 90% could be achieved with 100kV system. We introduce such a high potential of this new device for high voltage power switches.
This research was supported by Industrial Technology Research Grant Program in 2008 from New Energy and Industrial Technology Development Organization (NEDO) of Japan, and a part of this work was conducted at the Nano-Processing Facility, supported by IBEC Innovation Platform, AIST.
[1] D. Takeuchi et al., Phys. Status Solidi A 210 (2013) 1961.
3:00 AM - R2.02
HREM of Diamond Related MOS Structures
Jose Pinero 1 Daniel Araujo 1 Julien Pernot 2 Etienne Bustarret 2 Aboulaye Traore 2 Pilar Villar 1 Pierre Muret 2 Aurelien Marechal 2
1Universidad de Camp;#225;diz Puerto Real Spain2Institut Namp;#233;el Grenoble France
Show AbstractDiamond is the ultimate semiconductor for high power and high frequency applications due to his high breakdown electric field, elevated mobility and the outstanding thermal conductivity. Among such perspectives, diamond-based MOSFET and Schottky diodes are attractive architectures where the conducting or insulating behavior of the device is based on the electrostatic control of the band curvature at the oxide/semiconductor interface.
Recently, diamond-MOS structures showing outstanding electrical behavior have been achieved [1]. To verify the presence of the oxide layer, as well as to characterize several key parameters (like the oxide thickness, homogeneity and oxygen distribution) various transmission electron microscopy have been used. Among these techniques, HREM mode allows measuring thick oxide layers with atomic resolution that were previously identified using Electron Energy Loss Spectroscopy [2].
In this contribution, several diamond-MOS structures have been studied combining HREM/EELS techniques. Each diamond-MOS structure was previously electrically characterized, allowing to relate the measured electrical behavior with the physical nanostructure. Furthermore, MOS structures were annealed at different temperatures, showing a different electrical behavior. HREM/EELS observations were carried out in each anneal step, allowing not only to relate the electrical behavior with the nanostructure, but the evolution of this nanostructure with the annealing temperature.
[1] A. Traoré, P. Muret, A. Fiori, D. Eon, E. Gheeraert, and J. Pernot, Appl. Phys. Lett. 104, 052105 (2014).
[2] J. C. Piñero, D. Araujo, A. Traoré, G. Chicot, A. Maréchal, P. Muret, M. P. Alegre, M. P. Villar, and J. Pernot, Physica Status Solidi (a), n/a (2014)
3:15 AM - R2.03
Nearly 1000V Breakdown Characteristic of C-H Diamond Lateral MOSFETs with Al2O3 Gate Insulator
Tetsuya Yamada 1 Hidetoshi Tsuboi 1 Dechen Xu 1 Yuya Kitabayashi 1 Tatsuya Saito 1 Daisuke Matsumura 1 Atsushi Hiraiwa 1 Hiroshi Kawarada 1
1Waseda University Tokyo Japan
Show AbstractSurface conductive layer by hole carriers near hydrogen-terminated (C-H) diamond surface is also induced after high temperature (450 #8451;) atomic layer deposition of Al2O3 [1]. Recently, we have produced a number of field effect transistors operating at 400 #8451; and 500 V breakdown [2] using this C-H diamond.
Here, we report the lateral MOSFETs with better breakdown characteristics. In this study, the gate-drain distance LGD of MOSFETs was stepwise increased from 1 to 9 mu;m. The fabricated lateral MOSFETs showed good IDS-VDS characteristics, and their maximum breakdown voltages without field plate were 363 V with LGD of 1 mu;m, 392 V with 2 mu;m, 498 V with 5 mu;m, 591 V with 6 mu;m, 691 V with 7 mu;m and 996 V with 9 mu;m, respectively. The 996 V breakdown voltage is the highest of diamond FET reported in the past[3]. Moreover, the results are comparable to SiC[4] and GaN[5] lateral power FET in terms of gate-drain averaged electric field (VB/LGD) of 1 MV/cm, which is one of the important indicators to estimate the quality of lateral power device. The best VB/LGD was 3.6 MV/cm, with LGD of 1mu;m. This value exceeds the maximum VB/LGD of 1.7 MV/cm (AlGaN/AlGaN HEMT[6]) around lateral FETs and indicates excellent potential of a new lateral power FET using diamond. With field plate structure, higher breakdown voltage would be expected.
[Acknowledgment] This research was supported by research grants from ALCA (JST).
References
[1] A. Hiraiwa, H. Kawarada et al. J. Appl. Phys. 112, 124504 (2012).
[2] H.Kawarada, H. Tsuboi,T. Yamada, A.Hiraiwa et al., Appl. Phys. Lett, 105 (2014, in press).
[3] T. Iwasaki, M. Hatano et al., IEEE Elec. Dev. Lett, 35, 241-243 (2014)
[4] M. Noborio, T. Kimoto et al., IEEE Elec. Dev. Lett, 30, 831-833 (2009)
[5] S. L. Selvaraj, T. Egawa et al., IEEE Elec. Dev. Lett.33, 1375-1377 (2012).
[6] T. Nanjo, Y. Tokuda et al., IEEE Trans Elec. Dev, 60, 1046-1053 (2013)
3:30 AM - R2.04
High Voltage Characteristics and Interface Analysis of Diamond Lateral p-n Junction Devices
Takayuki Iwasaki 1 2 3 Junya Yaita 1 Kazuki Sato 1 Hiromitsu Kato 3 4 Toshiharu Makino 3 4 Masahiko Ogura 3 4 Daisuke Takeuchi 3 4 Takashi Yatsui 5 Hideyo Okushi 3 4 Satoshi Yamasaki 3 4 Mutsuko Hatano 1 2 3
1Tokyo Institute of Technology Tokyo Japan2ALCA Tokyo Japan3CREST Tokyo Japan4AIST Ibaraki Japan5The University of Tokyo Tokyo Japan
Show AbstractDiamond is one of promising materials for next generation low-loss power electronics due to its outstanding physical properties exceeding 4H-SiC and GaN. We have developed lateral p-n junction diodes [1] and junction field effect transistors (JFETs) [2-3]. In this study, we report a correlation of interface defects and leakage current in lateral p-n junction diodes, and also demonstrate high voltage operation of diamond JFETs composed of lateral p-n junctions.
Diamond lateral p-n diodes and JFETs were fabricated by a unique technique called selective growth of n+-diamonds [4]. After sidewalls of a boron-doped p-type film was exposed by ICP etching, n+-type diamonds were grown only at the sidewalls of the p-diamond. For JFETs, the p-diamond was shaped to a bar, which works as a channel. Thus, the current is controlled by depletion layers between the p-channel and n+-gates. The contact electrodes (Ti/Pt/Au) were fabricated by EB deposition and annealed to improve the contacts. I-V characteristics and breakdown voltages were measured in a vacuum chamber. Interface structure of the lateral p-n diodes was observed by cross-sectional TEM.
By cross-sectional TEM observations, dislocations were found at the interface of p-n diodes with large leakage currents, while good devices with very low leakage currents (below the measurement limit) have defect-free interface. The amount of dislocations is likely to be related with the leakage current level. Then, we examined breakdown characteristics of diamond JFETs composed of lateral p-n junctions with low leakage currents. At room temperature (RT), a breakdown voltage of 566 V was obtained with a gate voltage of 20 V [5]. This value corresponds to an electric field of 6.2 MV/cm, which is the highest in reported diamond FETs. We found that the breakdown occurred at the drain edge of the p-n junctions. Then, we measured the breakdown voltage at 473 K. The same JFET showed a higher breakdown voltage of 608 V. This fact indicates that the mechanism is avalanche breakdown, by which a breakdown voltage increases at a higher temperature due to the increase of phonon-scattering.
In summary, we investigated a relation of dislocation and leakage current in lateral p-n junction diodes. With the good p-n interface structure, we obtained high voltage operation of diamond JFETs. The device showed high breakdown voltages of 566 V and 608 V at RT and at 473 K, respectively.
References
[1] Y. Hoshino, et al., Phys. Status. Solidi A 209, 1761, 2012.
[2] T. Iwasaki, et al., Appl. Phys. Express 5, 091301, 2012.
[3] T. Iwasaki, et al., IEEE Electron Device Lett. 34, 1175, 2013.
[4] H. Kato, et al., Appl. Phys. Express 2, 055502, 2009.
[5] T. Iwasaki, et al., IEEE Electron Device Lett. 35, 241, 2014.
4:15 AM - *R2.05
Thermally-Stabilized H-Diamond MOS Field-Effect Transistors
Makoto Kasu 1
1Saga University Saga Japan
Show AbstractDiamond is expected to be used for ultimate high-power high-efficient transistors because of its superior physical properties. H-terminated diamond FETs showed very excellent RF and power performance such as a power-gain cut-off frequency (fMAX) of 125 GHz and a RF output power of 2.1 W/mm at 1GHz. However, thermal instability of electrical properties of H-terminated surface was a critical issue.
Recently, we found that the hole carriers are generated by NO2 adsorption in air on the H-terminated surface. With this method, we have increased the hole concentrations by one order of magnitude from ~1x1013 cm-2 to ~1x1014 cm-2 [1]. Their phenomena were well explained in terms of the SOMO level of NO2 molecules is positioned below the valence band maxima of H-diamond, and therefore, valence electrons transferred from H-diamond to the adsorbant [2].
We have also observed that Al2O3 passivation layer thermally stabilizes the H-diamond surface. After NO2 exposure to the H-diamond surface, thin Al2O3 passivation layer was deposited. Hall measurements revealed that the room-temperature hole sheet density (4.5x1013 cm-2) unchanged after repeated heating and cooling from -125 to 200o C [3].
With technologies of NO2 exposure and the Al2O3 passivation, we fabricated diamond MOSFETs, which showed excellent DC and RF charactertistics, and in which even after 200 o C heating in vacuum, maximum drain currents (IDSmax) were unchanged [4].
This success of diamond FETs encourages us to investigate electronic properties of MOS structures. First, by Synchrotron Radiation XPS/UPS/XANES measurements, we determined band offsets [5]. Next, by C-V measurements and analysis, we clarified two-dimensional hole properties formed at the MOS interface.
Acknowledgements: I appreciate deeply collaboration with Dr. K. Hirama of NTT and fruitful discussion with Prof. K. Shiraishi of Nagoya Univ., Profs. K. Takahashi, T. Oishi of Saga Univ. This work was partially supported by the Kakenhi, NEDO, the Mazda Foundation, and the Murata Foundation.
[1] M. Kubovic and M. Kasu et al., Appl. Phys. Express 2 (2009) 086502.
[2] Y. Takagi, K. Shiraishi, M. Kasu, and H. Sato, Surface Science 609 (2013) 203-206.
[3] M. Kasu, H. Sato, K. Hirama, Appl. Phys. Express 5 (2012) 025701.
[4] K. Hirama, M. Kasu et al., IEEE Electron Dev. Lett. 33 (2012) 1111-1113.
[5] K. Takahashi, M. Imai, K. Hirama, M. Kasu, Appl. Phys. Lett. 104 (2014) 072101.
4:45 AM - R2.06
Recent Progress in Diamond-Based Microplasma Devices
Ben Truscott 1 Chris Turner 1 Paul William May 1 Neil A Fox 1 Samantha Vincent 1
1University of Bristol Bristol United Kingdom
Show AbstractMicroplasmas are electrical discharges wherein one of the critical dimensions is <1 mm. Hollow-cathode microdischarges can achieve high densities with only moderate power input, and as their size decreases, their working pressure typically increases; indeed, for cavities with dimensions ~100 µm, operation has been demonstrated at atmospheric pressure. Arrays of microplasmas 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.
We recently presented the first results from an all-diamond microplasma device, in which the electrodes and the insulating dielectric were fabricated from boron-doped and undoped diamond, respectively, with the cavity formed by laser drilling a hole through all three layers. These devices operated at about 1 W d.c. power, and exhibited a sustaining voltage of 300-400 V for operation in up to 1 atm pressure helium.
We now present data from the second generation of these devices, with improved design and more comprehensive electrical diagnostics. The new devices are able to operate over a very wide range of currents and at up to 10 atm in He, striking reliably and functioning stably for many hours. Electrical characterization was performed using a high-voltage operational d.c. power supply (±#8239;1000 V, 0-40 mA), driven in voltage and current mode (for Paschen curve and current-voltage characteristic measurements, respectively) with a 0.1-100 Hz triangular waveform. Device voltages V and currents I were measured using high-side (high voltage) and low-side voltage probes connected to an oscilloscope, plus a low side current shunt. Various discharge phenomena, such as initiation, propagation, and extinction, were studied as a function of time during the voltage ramp cycle.
We find that the device Paschen curves (p×d vs V) closely resemble those for a Townsend discharge between parallel plate electrodes, despite the hollow cathode-type geometry. Current-voltage (I-V) characteristics are almost flat for all pressures and regardless of cavity dimensions, with sustaining voltages being typically 250-300#8239;V over the range I = 4-15#8239;mA, and only small differences arising with variations of pressure and discharge current.
In summary, we have now demonstrated, high pressure, high power density non-equilibrium glow discharges in monolithic diamond devices, with asymp;#8239;30#8239;min continuous operation at 9.5#8239;atm being achieved for the smallest (asymp;#8239;50#8239;µm) cavities. Operation at lower pressure and discharge current extends the device lifetime to days, and potentially weeks. We have also demonstrated plasma formation in 2D slots (200 µm wide × 1 mm long) and small (2×2; 3×3) cavity arrays.
5:00 AM - R2.07
Thermally Stable p-Diamond Schottky Barrier Diodes at 600 K
Alexandre Fiori 1 Tokuyuki Teraji 1 Yasuo Koide 1
1National Institute for Materials Science Tsukuba Japan
Show AbstractIn the past half-decade, diamond Schottky barrier diodes (SBD) are studied intensively for realizing high-performance rectifiers fulfilling both high-voltage blocking in reverse operation and low on-resistance in forward operation, which is difficult to achieve using common semiconductor materials. Several interesting results have been reported so far, but such diamond-based SBD electrical properties were not as good as expecting. One of the important subjects that should be studied is the thermal stability of diamond-based SBD, especially during its operation at the temperature higher than 500 K.
In this study, thermal behavior of tungsten carbide/p-diamond SBDs has been investigated. Reliable estimations of the Schottky barrier height (#981;B) and ideality factor (n) of theses SBDs were achieved by using a vertical SBD structure. Both #981;B and n measured at 300 K have been reduced through vacuum annealing at 600 K. In particular, #981;B decreased exponentially in time at 600 K, and stabilized at 1.4 eV after 90 minutes. The lowest n among SBDs examined was close to 1.0 at 600 K.
5:15 AM - R2.08
Stable Performance of C-H Bonds Diamond MOSFETs at 10K-673K
Dechen Xu 1 Hidetoshi Tsuboi 1 Tetsuya Yamada 1 Yuya Kitabayashi 1 Tatsuya Saito 1 Daisuke Matsumura 1 Atsushi Hiraiwa 1 Hiroshi Kawarada 1
1Waseda University Tokyo Japan
Show AbstractDiamond is a new attractive material in power device field because it has many exceptional characteristics such as wide-band gap, high thermal conductivity, high breakdown voltage, etc. So far, we have developed high performance field-effect transistors (FET) [1] by H-terminated (C-H) diamond surface where holes are accumulated densely. Since the C-H surface was affected by external environment, the surface protection is required. Recently, we applied atomic layer deposition (ALD) of Al2O3 [2,3] at 450#730;C [4] as passivation. Even after the annealing at 550°C in air the hole density were preserved [5]. Here we fabricated metal oxide semiconductor (MOS) FETs with temperature resistant Al2O3 film, and successfully evaluated C-H diamond MOSFETs electrical properties from 10K to 673K (#65293;263°C~400°C).
C-H diamond MOSFETs using Al2O3 film was produced by following method. First 500nm-thick undoped layer was deposited on (100) Ib diamond by PECVD and Ti/Au were deposited as source and drain electrode. Second the channel surface was H-terminated by remote plasma. Third Al2O3 as gate oxide and passivation were deposited by ALD (oxidation source: H2O) at 450°C [4]. Al gate electrode was formed on the Al2O3 gate insulator.
We measured IDS - VDS and IDS - VGS characteristics of the diamond power devices at 10K-673K with two different Al2O3 film thickness 32nm and 200nm in vacuum. Drain current value decreased when the temperature is higher than 573K (300°C) or lower than 273K (0°C). However, even at near the absolute zero temperature (#65293;263#730;C), the current value degradation was less than 50% of both ALD-Al2O3 MOSFETs. The mobility degradation at high temperature and the contact resistance increase at low temperature caused the drain current decrease. The latter can be eliminated if higher workfunction metal such as Au can be used. In addition, good pinch-off of the drain current density is obtained at 673K (400#730;C). The on-off ratio of both ALD-Al2O3 MOSFETs is 109, and 108 at 10K and room temperature. Due to leakage current increases as the temperature rose to 673K (400#730;C), the on-off ratio of ALD-Al2O3 (32nm) MOSFET decreased to 103, and the ALD-Al2O3 (200nm) MOSFET decreased to 102. At 10K-673K the change ratio of max transconductance in both ALD-Al2O3 MOSFETs performed excellent characteristic, only 50% in ALD-Al2O3 (32nm) MOSFET and 25% in ALD-Al2O3 (200nm) MOSFET. As a result, we confirmed both ALD-Al2O3 MOSFETs can stably operate at wide range temperature and low temperature dependence of current was obtained as compared with those of the boron-doped diamond MOSFET.
This research was supported by research grants from ALCA (JST).
[1] H. Kawarada et al., Appl. Phys. Lett. 65, 1563 (1994).
[2] D. Kueck, E. Kohn et al., Diam. Relat. Mat. 19 166 (2010).
[3] M. Kasu et al., APEX 5, 025701(2012).
[4] A.Hiraiwa, H.Kawarada et al. J. Appl. Phys. 112(12), 124504 (2012).
[5] A Daicho, A. Hiraiwa, H. Kawarada et al., J. Appl. Phys. 115,223711 (2014).
5:30 AM - R2.09
Defect Reduction in Single Crystal Boron Doped Diamond for Improving Schottky Barrier Diode Performance
Shannon Nicley Demlow 1 Stephen Zajac 1 Robert Rechenberg 2 Michael Becker 2 Timothy A. Grotjohn 1
1Michigan State University East Lansing USA2Fraunhofer USA Center for Coatings and Laser Applications, Inc. East Lansing USA
Show AbstractDue to its exceptional thermal conductivity, wide bandgap, high breakdown electric field strength and combined carrier mobilities, diamond has the potential to revolutionize high-power and high-frequency electronics. The vertical architecture Schottky Barrier diode (SBD) is a particularly promising high-power application for diamond. Although vertical architecture devices have the potential to significantly outperform pseudo-vertical structures [1], up until now primarily pseudo-vertical structures have been investigated because of the difficulties in fabricating the vertical device structures. However, much progress has been made recently toward the reliable fabrication of the heavily doped ( > 1020 cm-3), free standing ( > 300 mu;m thick) p-type substrates that are needed for these structures. In our previous work investigating heavily boron doped single crystal diamond [2-3] we studied the plasma gas-phase to grown solid-phase boron-to-carbon ratio, and have shown a temperature dependence to this doping efficiency. We have additionally shown a temperature dependence for the formation of unepitaxial crystallites, which is a significant result, since unepitaxial crystallites are known to adversely affect SBD performance [4]. The etch-pit density associated with crystalline dislocations has also been shown to be adversely related to the reverse characteristics of SBDs [4]. Strategies for the reduction of screw- and edge-type threading dislocations in CVD diamond have been demonstrated [5], but up to now such strategies have not been effectively employed for the improvement of diode characteristics.
This work expands upon our previous effort to grow and characterize high-quality diamond for electrical applications. An SBD architecture is proposed for the reduction of threading type dislocations in the active region of the fabricated diodes. SBD performance will be evaluated, and discussed in the context of the dislocation density. Single crystal boron doped diamond films of high and low doping levels are deposited homoepitaxially in a microwave plasma-assisted chemical vapor deposition (MPACVD) bell-jar reactor with feedgas mixtures including hydrogen, methane, and diborane. We report on the results of growth experiments, and characterize the grown diamond by electrical measurements, FTIR, and SIMS. The formation and effect of defects will additionally be analyzed using etch pit techniques and Birefringence measurements.
References
[1] J. Achard et al.,Diamond and Related Materials, 20 (2011) 145
[2] S.N. Demlow, R. Rechenberg and T.A. Grotjohn “The Effect of Substrate Temperature and Growth Rate on the Doping Efficiency of Single Crystal Boron Doped Diamond.” Diamond and Related Materials, (2014) In Press - Accepted
[3] S.N. Demlow, et al.,MRS Proceedings, 1395, (2012)
[4] N. Tatsumi, et al.,SEI Technical Review 68 (2009) 54
[5] I. Friel, et al.,Diamond and Related Materials,18 (2009) 808
5:45 AM - R2.10
Fabrication of Diamond Rods for Power Device Application
Mikinori Kobayashi 1 Masafumi Inaba 1 Mohd Syamsul Nasyriq Samsol Baharin 1 Atsushi Hiraiwa 1 Hiroshi Kawarada 1
1Waseda University Tokyo Japan
Show AbstractDiamond has unique properties, for example, hole carriers are densely accumulated on a carbon-hydrogen bond of the diamond surface (2DHG). Using this conductive layer, we have developed high-performance field-effect transistors (FETs)[1]. Convenience to use the 2DHG, planar-type devices have been made on H-terminated diamond surface mainly. But it is required making vertical-type devices in order to create integrated power FETs that handle a large current. Other materials of the power device, GaN has been studied as an example. GaN devices are using two-dimensional electron gas (2DEG) in the AlGaN / GaN interface, and are common in utilizing 2DHG in diamond. However, when applying these materials to the vertical structure, 2DEG can&’t be formed in GaN because of lack of polarization on the sidewall of wurtzite structure, but 2DHG can be formed in diamond easily by C-H polarization. H-termination of diamond is advantageous in that it can be formed anywhere on the diamond. Although the H-termination is affected by surroundings, we solve the challenge by passivation technique using atomic layer deposition (ALD) Al2O3 at 450 #730;C [2]. We have developed an advanced passivation for the surface p-type conduction operated at high temperature (450#8451;) using atomic layer deposition of Al2O3 film and achieved the good breakdown characteristic of MOSFETs. This result is comparable to the lateral FET characteristics using SiC or GaN[3], and further improvement can be expected by applying this diamond FET structure to vertical FETs. In this work, we fabricated the 3D rod structure on mono-crystalline diamond and investigated conductivity due to the 2DHG of the side walls of the rods. This study will contribute to the vertical-type MOSFET structure using surface conduction of the diamond.
Processing of the surface shape of the diamond has been reported in the formation of nanowires [4,5]. These reports showed the fine shape control by inductively coupled plasma ion etching (ICP-RIE). In this study, we fabricated diamond rods with ICP-RIE with oxygen etchant. Patterned gold patches were deposited by electron-beam evaporation on the mono-crystalline diamond (001) surface using photo-lithography technique. In order to create 2DHG at sidewalls of diamond rods, surface hydrogenation was performed by remote plasma CVD method. Conductive AFM was utilized to measure the conductivity of sidewalls of small dimer diamond rods by possible contact with the fine area. The quantitative data is going to be shown in the symposium.
[Acknowledgment] This research was supported by research grants from ALCA (JST).
References
[1] H.Kawarada, Surf. Sci. Rep. 26 (1996) 205.
[2] A. Hiraiwa, H. Kawarada et al J. Appl. Phys. 112, 124504 (2012).
[3] M.Noborio, T.Kimoto et al., Electron Devices, IEEE Transactions. 54 (2007) 1216-1223.
[4] Y.Ando, A.Sawabe et al., Diam. Relat. Mat. 13 (2004) 633-637.
[5] B. J.M. Hausmann, M. Lon#269;ar et al., Diam. Relat. Mat. 19 (2010) 621-629.
R3: Poster Session
Session Chairs
Robert Nemanich
Ken Haenen
Oliver Williams
Monday PM, December 01, 2014
Hynes, Level 1, Hall B
9:00 AM - R3.01
Metal Nanoparticle-Embedded Porous Diamond Spherical Particles
Takeshi Kondo 1 2 3 Takuji Morimura 1 Tatsumi Tsujimoto 1 Eriko Kai 1 Tatsuo Aikawa 1 2 Makoto Yuasa 1 2 3
1Tokyo University of Science Noda Japan2Tokyo University of Science Noda Japan3JST ACT-C Noda Japan
Show AbstractWe have developed micrometer-sized porous diamond spherical particle (PDSP) as a new porous diamond material. The PDSP has mesopores with a diameter of ca. 10 nm and its BET surface area is ca. 300 m2/g. Since diamond is a chemically inert material, the PDSP should be useful for a stable catalyst support. In this study, metal nanoparticle-embedded PDSPs were fabricated and their application to a stable catalyst was investigated. An aqueous slurry containing nanodiamond (ND), platinum nanoparticle (PtNP) and polyethylene glycol (PEG) was spray-dried to form an ND/PtNP/PEG composite spherical particle. After removal of PEG from the particle by air oxidation, the treated particle was subjected to microwave plasma-assisted chemical vapor deposition for a short time to obtain PtNP-embedded PDSP (PtNP@PDSP). From the STEM observation, PtNP was found to be dispersed in the PtNP@PDSP. The catalytic activity of the PtNP@PDSP was estimated with cyclohexane dehydrogenation reaction as a model reaction, and was found to be more active than that of PtNP-supported carbon black. Similarly, PdNP@PDSP was fabricated and its catalytic activity to Suzuki coupling reaction was also investigated.
9:00 AM - R3.02
Enhanced Capacitance of Composite Boron-Doped Diamond / TiO2 Nanotube Electrodes Studied by Impedance Spectroscopy
Robert Bogdanowicz 1 Katarzyna Siuzdak 2 Michal Sobaszek 1 Miroslaw Sawczak 2
1Gdansk University of Technology Gdansk Poland2Polish Academy of Sciences, The Szewalski Institute of Fluid-Flow Machinery Gdansk Poland
Show AbstractWe report the novel composite nanostructures based on TiO2 nanotubes over-grown by thin boron-doped diamond film. The BDD-modified titania nanotubes nanostructures shows increase of sensitivity and performance when used as an electrodes in electrochemical environments.
The thin BDD films (~200-500 nm) were deposited using microwave plasma assisted chemical vapor deposition (MW PA CVD) onto anodically fabricated TiO2 nanotube arrays. The influence of boron doping level, methane admixture and growth time on performance of the Ti/TiO2/BDD electrode have been particularly studied.
Numerical analysis of scanning electron microscopy (SEM) was applied to investigate surface morphology and grains size distribution. Controlling of the grain size is key parameter that influence on greater surface development witch corresponding to increasing capacity. Moreover, the chemical composition of Ti/TiO2/BDD electrodes was investigated by means of micro-Raman Spectroscopy.
Electrochemical measurements composite electrodes were performed by the potentionstat-galvanostat system AutoLab PGStat 302N in a standard three-electrode assembly at 295 K. Different types of Ti/TiO2/BDD layers and as reference Ti/BDD stayed as a working electrode. The counter electrode consisted of Pt mesh and an Ag/AgCl/0.1 M KCl electrode was the reference electrode. Electrodes with geometrical surface area of 1 cm2 were tested by cyclic voltammetry in solutions: 0.1M NaNO3 without and with 1 mM K3Fe(CN)6. Prior to taking electrochemical measurement, a pretreatment was performed in which working electrode was held at -0.1 V for 60 s. Electrochemical impedance spectroscopy measurements were carried out at the formal redox potential +0.13V vs. Ag/AgCl/0.1M KCl in the frequency range of 0.1 to 1000 Hz and amplitude 10 mV rms. All the electrolytes were purged with argon for 50 min. before electrochemical test and during measurements there was an Ar-cushion above the electrolyte.
In general all the composite electrodes TiO2/BDD are characterized by the significantly higher current than BDD layer deposited directly onto the Ti substrate. The registered current increases with the boron concentration that could be related to the higher surface area and increase in conductivity. Analysis of electrochemical impedance spectra according to proposed electric equivalent circuit: Re[Q1R1][Q2(R2W)] allows to determine surface area on the basis of value of constant phase element.
9:00 AM - R3.03
Phosphorus Doped Diamond Homoepitaxy Using Trimethylphosphine
Franz A Koeck 1 Robert J Nemanich 1
1Arizona State University Tempe USA
Show AbstractDoped diamond for electronic devices requires p and n-type material with sufficient doping concentration. While p-type diamond can be readily realized through boron doping the preparation of n-type electronic grade diamond is still a challenge. One of the most suitable donors for n-type diamond is phosphorus. Several groups have focused their doping studies utilizing phosphine gas, a highly toxic compound comprised of hydrogen and phosphorus. We report on doping results of (100) single crystal diamond using trimethylphosphine, P(CH3)3, in a microwave plasma assisted CVD process. The substrates, type IIa (100) plates, were chemically cleaned and an initial undoped diamond layer was deposited using methane and hydrogen. For the phosphorus doped layer a trimethlyphosphine/hydrogen mixture and hydrogen was used without additional methane flow. At a microwave power of 1300W and a chamber pressure of 70 torr the substrate temperature approached 850 °C. The growth temperature was adjusted by controlling the pressure and the microwave power where we prepared films with microwave power up to 2500W, pressure up to 90 torr and growth temperature up to ~1130 °C. At the lower microwave power phosphorus incorporation evaluated through SIMS exceeded 1017 cm3. However, with increased microwave power the phosphorus incorporation slightly exceeded 1018 cm-3. Increasing the growth temperature at higher microwave power through increased pressure resulted in a small increase in the phosphorus concentration in the film. These results evidence an advantageous effect of microwave power and growth temperature on the doping concentration. The doping results indicate that trimethylphosphine should be an efficient doping source for n-type diamond. Film morphology was described in terms of a step-bunch growth mode resulting in a homoepitaxial film with patterned roughness.
This research is supported by the Advanced Research Projects Agency - Energy (arpa-e).
9:00 AM - R3.04
Electric Property of SiO2/Diamond Structure
Yuji Seshimo 1 Takeshi Hara 1 Yuya Hayashi 1 Tomohiro Hakamata 1 Wako Ono 1 Atsushi Hiraiwa 1 Hiroshi Kawarada 1
1Waseda Univ. Shinjyuku Japan
Show AbstractWe have used Al2O3 as gate insulator of diamond MOSFET and achieved high voltage (~500V)[1] and high temperature operation (~400#8451;)[1]. But SiO2 gate insulator should be used for because of its high reliability. Diamond device is also expected to get high reliability by using SiO2 gate insulator for practical application. Thermal oxidation of Si is the most suitable gate-insulator for Si MOSFET. So, we thermally oxidized Si film deposited in MBE apparatus which hardly affect the termination structure of diamond.
First, we formed p-type surface conductive layers (1×104Omega;/sq) on (001)-oriented single crystalline diamond substrates using hydrogen plasma. Then, the samples were anneled at 300#8451;to clean surface thermally in MBE apparatus. After cooling down to room temperature, we deposited Si on diamond substrates in 50-100 nm in thickness. The deposition temperature was between room temperature-300#8451;.
At room temperature deposition, Si kept amorphous from the beginning to the end at room temperature deposition by RHEED pattern However, at 300#8451;deposition, Si changed amorphous to polycrystal in the middle of deposition of 56nm in thickness. This change of crystallinity is similar to Si-molecular beam deposition on Si substrates[2]. The XPS result of diamond surface,
which is exposed by removing Si thin layer (or SiO2 layer formed by air-exposuring) deposited at room temperature by hydrofluoric acid had no Si peaks. Due to this result, C-Si bonds formed at 600#8451; did not appeared. Consequently, C-H bonds on diamond surface was not replaced by other bonds and preserved in the interface of Si/diamond. We will conduct same experiment on (111)-oriented crystalline diamond. The influence of thermal oxidation on electric properties are discussed in the presentation. .
Acknowledgements
This study was supported by research grants from ALCA (JST) and JSPS.
References
[1] H.Kawarada, H. Tsuboi,T. Yamada, A.Hiraiwa et al., Appl. Phys. Lett. 105 (2014, in press).
[2] M. Tabe, K.Arai, et al, Jpn J. App. Physic. 20, 703-708 (1981).
9:00 AM - R3.05
Nitrogen and Silicon Defect Incorporation during Homoepitaxial CVD Diamond Growth on (111) Surfaces
Samuel L. Moore 1 Yogesh K. Vohra 1
1University of Alabama at Birmingham (UAB) Birmingham USA
Show AbstractChemical Vapor Deposited (CVD) diamond growth on (111) diamond surfaces has received increased attention lately because of the use of N-V related centers in quantum computing as well as application of these defect centers in sensing extremely low levels of magnetic field. This magnetic sensing is of interest in studying the properties of materials under extreme conditions in a diamond anvil cell. We have carried out a detailed study of homoepitaxial diamond deposition on (111) diamond surface using a 1.2 kW microwave plasma chemical vapor deposition system utilizing a methane/hydrogen/nitrogen/oxygen chemistry. We have utilized Type Ib (111) oriented diamond as seed crystals in our study. The homoepitaxial grown diamond films were analyzed by Raman spectroscopy, Photoluminescence spectroscopy, Atomic Force Microscopy X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy, and single crystal x-ray diffraction. The nitrogen concentration in the plasma was carefully varied between 0 and 1500 ppm while the ppm level of silicon impurity is present in the plasma from the quartz bell jar. The concentration of N-V defect center and Si-defect center was quantitatively studied through monitoring of the zero phonon lines with the varying growth conditions. Higher concentration of nitrogen in the plasma was observed to suppress silicon incorporation. The role of plasma chemistry and surface roughness of the seed crystals in growing a high quality homoexpitaxial diamond film with controlled incorporation of N-V defect centers on (111) diamond surface will be presented.
Our research results are based upon work supported by the National Science Foundation Partnerships for Innovation: Building Innovation Capacity (PFI: BIC) subprogram under Grant No. IIP-1317210.
9:00 AM - R3.06
Surface Roughness and Critical Exponents Analyses of Boron-Doped Diamond Films Using Atomic Force Microscopy Imaging: Application of Autocorrelation and Power Spectral Density Functions
Sanju Gupta 1 Gregory Vierkant 1
1Western Kentucky University Bowling Green USA
Show AbstractThe surface roughness evolution of growing thin films of metals or semiconductors provides much needed information about their growth kinetics and corresponding mechanism. While some systems show stages of nucleation, coalescence and growth, the others exhibit varying microstructures with different process conditions. In view of these classifications, we hereby report detailed analyses relating the atomic force microscopy (AFM) characterizations to extract the surface roughness and growth kinetics exponents of relatively lower boron-doped diamond (BDD) films by utilizing the analytical power spectral density (PSD) and autocorrelation function (ACF) mathematical function tools. The machining industry has applied PSD for a number of years for the tool design, wear and machined surface quality. Hereby, we present similar analyses at mesoscale to study the surface morphology as well as quality of BDD films grown using microwave plasma-assisted chemical vapor deposition (MPACVD) technique. PSD spectra as a function of boron concentration (in gaseous phase) are compared with those grown without boron. We find that relatively higher boron concentration yielded higher amplitudes in the longer wavelength power spectral lines with amplitudes decreasing in an exponential or power law fashion towards the shorter wavelengths determining the roughness exponent (a ~ 0.16±0.03) and growth exponent (b ~ 0.54), albeit indirectly. A unique application of the ACF function, widely used in signal processing, was also applied to one-dimensional or line analyses (i.e. along the x- and y- axes) in AFM images revealing surface topology data sets with varying boron concentration. Here, the ACF was used to cancel random surface ‘noise&’ and identify any spatial periodicity via repetitive ACF peaks or spatially correlated noise. Periodicity at shorter spatial wavelengths was observed for un-doped and low doping levels, while smaller correlations were observed for the relative higher boron concentration. These semi-quantitative spatial analyses may prove useful in comparing synthesis techniques and films grown with varying compositional makeup of diamond films and other technological important electronic materials. These findings in terms of ‘critical exponents&’ are also correlated with traditional Raman spectroscopy (RS) and X-Ray Diffraction (XRD) structural properties thus helping to provide an insight into the growth kinetics albeit in reverse manner.
9:00 AM - R3.07
Sensitive Electrochemical Detection at Screen-Printed Diamond Electrodes
Ikuto Udagawa 1 Takeshi Kondo 1 2 3 Tatsuo Aikawa 1 2 Isao Shitanda 1 2 Yoshinao Hoshi 1 2 Masayuki Itagaki 1 2 Makoto Yuasa 1 2 3
1Tokyo University of Science Noda Japan2Tokyo University of Science Noda Japan3JST ACT-C Noda Japan
Show AbstractConductive diamond electrode has attracted attention as a highly sensitive and stable electrode material in a wide electrochemical application field. However, the shape that can be made is limited because it is deposited on a flat substrate material as a thin film. We have fabricated screen-printed diamond electrodes that can be made into an arbitrary shape with a lower temperature procedure, and can be applied to mass production. In this study, we prepared screen-printed diamond electrode with different binder/BDDP ratios, and the electrochemical properties were investigated. BDD powder (BDDP) was obtained by microwave plasma-assisted CVD method using diamond powder (DP) as a substrate material. An ink containing BDDP and polyester binder was used for preparation of the screen-printed electrode. For a large binder/BDDP ratio, the screen-printed diamond electrode showed a microelectrode-like voltammetric behavior, while an electrode with a small binder/BDDP ratio exhibited typical planar electrode behavior. This should be because that the micrometer-sized conductive domains were exposed on the electrode surface with a low density for the large binder/BDDP electrode. Based on the microelectrode effect, large signal-to-background ratios were obtained for electrochemical detection of ascorbic acid. Thus, the screen-printed diamond electrode with a large binder/BDDP should be useful for a disposable and sensitive electrode material.
9:00 AM - R3.08
Nitrogen and 13C Delta Doping of Diamond for NV Centers and Nanomagnetic Sensing Applications
Gary L. Harris 1
1Howard University Washington USA
Show AbstractThe nitrogen-vacancy (NV) center is an individually addressable electronic spin in diamond that can be initialized and read out optically and coherently controlled with microwaves at room temperature. These properties require NV centers to be located within a few nanometers of the surface and within 2 nanometers of 13C for long term spin applications. Engineering NV centers near the surface have not been fully characterized. We report on a hot filament growth chemical vapor deposition (HF-CVD) delta doping method that is very promising for both the NV center and 13C doping. The doping is on the order of 10-100 nm. In-situ laser reflectance interferometry tool (LRI) is used for monitoring growth characteristics of diamond thin film materials. The grown epi-layers were characterized using scanning electron microscopy, Raman spectroscopy, Atomic force microscope PL, and hall measurements for electron mobility measurements
9:00 AM - R3.09
Work Function Measurements of Co-Doped Diamond Thin Films with Different Surface Terminations Using UHV Kelvin Probe Force Microscopy (KPFM)
Hugo Dominguez Andrade 1 Sarah C Halliwell 1 M Zamir Othman 2 James O Thomas 1 Neil A Fox 2 1 Paul W May 2
1University of Bristol Bristol United Kingdom2University of Bristol Bristol United Kingdom
Show AbstractOver the past decade, diamond films have been studied for use energy conversion devices such as thermionic energy converters. One crucial property of diamond films for thermionic emission is its surface work function, which depends on the type and concentration of impurities used to dope the diamond as well as its surface termination. It is desirable to reduce the diamond work function which leads to an increase in emitted current and therefore to a higher power output on a potential device.
Several techniques are available to characterise the work function, namely Ultra-violet Photoelectron Spectroscopy, Kelvin Probe or extrapolation from thermionic emission data. However, these only provide an average value of the surface work function making it difficult to extract more detailed information about the material in question. Alternatively, kelvin probe force microscopy (KPFM) is an AFM technique that can map topography and surface contact potential difference (CPD) with a lateral resolution of a few nanometres and a energy resolution of tens of milivolts. Using a calibration process it is possible to convert surface CPD into work function values so that the work function variation between different crystals due to crystallographic orientation can be distinguished. If the surface is subjected to a particular surface termination procedure it is also possible to detect if this has had any effect on the local work function and whether the coverage is as uniform as expected.
Here, we report the effects on the diamond work function produced by introducing Li, B and N impurities into the diamond lattice to act as a novel co-dopant cluster offering an alternative to traditional dopants like B or N. For this task we performed KPFM under UHV conditions showing the work function of different co-doped diamond films. The effect of a number of different surface terminations on the work function will also be presented.
9:00 AM - R3.10
Routes to Control the Chemical Potential and to Modulate the Reactivity of Nanodiamond Surfaces
Giacomo Reina 1 Stefano Gay 1 Silvia Orlanducci 1 Emanuela Tamburri 1 Teresa Lavecchia 1 Maria Letizia Terranova 1
1University Tor Vergata of Rome Roma Italy
Show AbstractThe use of nanodiamond (ND) for drug delivery and bio-imaging is grounded on chemical functionalization, and the key task to be addressed is the capability to simplify the process steps, to reduce the process times and to maximizing the drug/ligand uptake. The idea underlying the present research is to modulate loading capabilities of ND by controlled modification of their chemical surface potential. To this aim the ND samples are treated either by wet chemistry using medium-strong reducing agents or by tuneable H-plasmas produced in a custom- designed MW-RF reactor.
SERS-aided micro-Raman spectroscopy and FTIR allow us to precisely detect structural and chemical features of both core and surface of the NDIA after the various treatments .
A further important result is the quenching , obtained by specific processes, of the radical behaviour of the NDIA surfaces. This achievement reduces the possibility of uncontrolled reactions between NDIA and chemical species and helps in controlling the related biochemistry . Several chemical and physical methodologies are used in order to investigate how the properties imparted to NDIA surfaces affect the uptake of molecules .
The affinity of the treated surfaces for drugs has been probed by conjugating a series of natural antioxidant molecules and by testing in vitro the ND-drug adducts as chemioterapics.
The methodology developed to modify the ND surfaces and to precisely identify their chemistry, are offering practical solutions to the still open problems related to NDIA-based systems for bio-medical applications
9:00 AM - R3.11
Electrical Characterization of Diamond/Boron Doped Diamond Nanostructures for Use in Harsh Environment Applications
Lukasz Golunski 1 Norbert Kwietniewski 2 Piotr Plotka 3 Robert Bogdanowicz 1 Marc Bockrath 4 Lukasz Burczyk 5
1Gdansk University of Technology Gdaamp;#324;sk Poland2Warsaw University of Technology Warsaw Poland3Gdansk University of Technology Gdansk Poland4University of California, Riverside Riverside USA5Gdansk University of Technology Gdansk Poland
Show AbstractThe polycrystalline boron doped diamond (BDD) shows stable electrical properties and high tolerance for harsh environments (e.g. high temperature or aggressive chemical compounds) comparing to other materials used in semiconductor devices. In this study we have designed electronic devices fabricated from non-intentionally/low boron doped diamond (NiD/LBDD) films and highly boron doped diamond structures. Presented semiconductor devices consist of highly boron doped structures grown on NiD/LBDD diamond films. Created structures were analyzed by electrical measurements for use in harsh environment applications. Moreover, the boron-doping level and influence of oxygen content on chemical composition of diamond films were particularly investigated.
Microwave Plasma Enhanced Chemical Vapor Deposition (MW PE CVD) has been used for thin diamond films growth. Non-intentionally doped diamond and low boron doped diamond (0-2000 ppm [B]/[C]) films have been deposited on the Si/SiO2 wafers with different content of carbon, boron and oxygen. In the next step, the surface conductivity introduced by hydrogen termination were removed. Then, the shape of the highly doped diamond structures were obtained by pyrolysis of SiO2 on NiD film and standard lithography process. The highly doped structures were obtained for different growth time and [B]/[C] ratio (4000 - 10000 ppm). The narrowest distance between two highly doped structures was 5µm. The standard Ti/Al/Au ohmic contacts were deposited using physical vapor deposition for electrical characterization of NiD/BDD devices. The influence of diffusion boron from highly doped diamond into non-doped/low-doped diamond film was investigated. Semiconductor character of NiD/BDD structures was preserved with relatively high sp3/sp2 band ratio. Surface morphology of designed structures was analyzed by Scanning Electron Microscope and Atomic Force Microscope. The relative sp3/sp2 band ratios were determined by deconvolution of Raman spectra. The resistivity of the NiD and LBDD film was studied using four-point probe measurements. DC and high frequency studies were performed to test the operation of the NiD/BDD devices in temperature range up to 600oC exposed on acidic environment.
9:00 AM - R3.12
Effects of Fluorine Incorporation on the Structural and Electrical Properties of Diamond-Like Carbon
Kento Nakanishi 1 Jun Otsuka 1 Masanori Hiratsuka 2 Tetsuya Suzuki 1 Akira Shirakura 1 Chen Chung Du 3
1Graduate School of Science and Technology, Keio University, Japan Kohoku-ku Japan2Nanotec Corporation Kashiwa Japan3Industrial Technology Research Institute Primary Employment Sector Hsinchu China
Show AbstractDiamond-like carbon (DLC) has received great attention as a new material for application to thin film solar cells and other semiconducting devices. DLC can be produced a lower cost than amorphous silicon which is utilized for solar cells today. However, the electrical properties of DLC are insufficient. To solve this problem, we investigated the effects of DLC fluorination on its structural and electrical properties. We prepared five kinds of fluorinated DLC (F-DLC) thin films which had different amounts of fluorine on the polycarbonate (PC), transparent conductive oxide (TCO) grass and polyethylene naphthalate (PEN) substrates. The films were deposited by the radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) method. C6H6 and C6HF5 were used as source gases. After analyzing DLC properties, to manufacture the solar cell, we prepared nitrogen doped DLC (F-DLC) thin films using N2 gas as a doping gas. Surface chemical compositions and carbon bonding structure were analyzed by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electron spin resonance (ESR). The surface resistivity was measured by the dual-ring method. The current-voltage (I-V) characteristics of the nitrogen doped F-DLC films /p-Si structures were measured with a solar simulator under AM 1.5 condition. The fluorine had been incorporated from 0 to 20 atom % into the DLC films which was discovered by XPS. Moreover, XPS analysis of the carbon spectra after fluorine saturation at 10 atom % showed the majority of bonding was C-F bonding. At 20 atom % fluorine content, C-F2 bonding was observed in the addition to C-F bonding. As the amount of fluorine increases, Raman spectra show the intensity of the D band increases with respect to the G band. The width of the ESR spectra became broader. The surface resistivity of the films changed from 3.57×1012 to 4.55×109. Its values dropped to a minimum at 10 atom % fluorine content. Moreover, the energy conversion efficiency reached the maximum level in this case. Fluorination of DLC affects electrical properties. At first the surface resistivity decreases, because of π electron delocalization according to ESR spectra. After that the surface resistivity increases because the chain structure domains of DLC becomes larger. There are two reasons for this. First, XPS shows C-F2 bonding within F-DLC which prevent ring structures. Second, the Raman spectra indicated that the sp2 domains decreased. With a larger chain structure domain, the surface resistivity typically increased. We succeeded in improving the energy conversion efficiency and its electrical conductivity. Our results indicate the necessity of the application of DLC fluorination to the semiconducting material for electrical devices such as solar cells.
9:00 AM - R3.13
Theoretical Studies of Li-N/Li-B Co-Doping in Diamond as a Route to n-Type Dopants
M. Zamir Othman 1 Neil L. Allan 1 Neil A. Fox 1 Paul W May 1
1University of Bristol Bristol United Kingdom
Show AbstractDespite recent advances with phosphorus doping of diamond, the production of n-type semiconducting diamond with useful electronic characteristics remains elusive. Lithium has been suggested as a possible alternative n-type dopant due to its potential as a shallow donor in diamond. However, experimentally doping with lithium is difficult to achieve due to the low solubility of Li in diamond, and its relatively high mobility which allows it to diffuse through the lattice at fairly low temperatures.
It has been suggested that the unwanted Li diffusion can be prevented by adding substitutional nitrogen or boron together with interstitial Li, with the N or B 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 investigated the defect formation energy, the band structure and density of states (DOS) of diamond containing various Li-N/Li-B centres, using calculations based on periodic Density Functional Theory (DFT) as implemented in the CASTEP code. The calculations use the PBE functional with a cubic supercell containing 64 atoms. Interstitial lithium and/or a substitutional nitrogen/boron atom are included in the supercell and the effect of neighbouring vacancies is also taken into account. The band structures and DOS of the co-doped material are compared with those of the separate singly doped systems. The results of this computational study will provide guidance for developing practical routes to realise these dopant systems experimentally.
9:00 AM - R3.14
Growth and Characterization of High Quality, Large Single Crystal Diamond Substrates (SCD)
Shreya Nad 1 2 Yajun Gu 2 Jes Asmussen 2 3
1Michigan State University East Lansing USA2Michigan State University East Lansing USA3Fraunhofer USA Inc., Center for Coatings and Laser Applications East Lansing USA
Show AbstractExciting properties of diamond like extreme hardness, chemical inertness and wide band gap can be exploited for utilization in high power electronics and high power optical components in harsh conditions. The main obstacle in using single crystal diamond substrates for these applications has been the synthesis of large (>1 cm2), high purity and defect-free SCDs to overcome the problem of grain boundaries arising in polycrystalline diamond (PCD) substrates.
There are several approaches for large SCD synthesis. One is by using the mosaic method. By precisely aligning tiled clones of grown CVD SCD, it is possible to enlarge SCDs. Another approach is by using side-seed growth along <100> direction to increase the seed growth area and then grow along the original direction for a final large SCD. Both these approaches lead to stress along the boundaries of different growth directions or misalignment which thereby lead to defects in the substrates. A third approach is to use heteroepitaxial growth of SCD on large non-diamond substrates. This needs more work to remove defects created by diamond islands formed on the substrate.
Here, we investigate methods of increasing the area of SCD during synthesis. It is important to mitigate the growth of the PCD rim which reduces the required SCD surface area. We have conducted experiments using several variations of open and pocket holders. By adjusting the dimensions of the pocket holder, we can minimize the rim. It is observed that by using these holders, the PCD rim can be reduced by a factor of 2 or more in comparison to open holders. The difference in electric field concentration around the seed edges leads to different thicknesses of PCD rim. By designing novel substrate holders which allow the growth of diamond in both longitudinal and lateral directions, due to the absence of the rim, will help in obtaining thick large SCD substrates.
By using a series of pocket holders we have grown high quality (< 300ppb [N] impurities), thick (~ 2.2mm) SCDs on 3.5 x 3.5mm2 type Ib HPHT seeds. High growth rates of 25 - 32µm/h were achieved. These substrates have been synthesized via microwave plasma assisted CVD in a microwave cavity plasma reactor [1] whose operating conditions have been optimized for an efficient process [2].
Threaded dislocations arising from the HPHT seeds propagate parallel to growth direction <100> [3]. After removing the HPHT seed and by flipping the grown CVD SCD by 90° for another synthesis step, the propagation of the dislocations can be minimized. By subsequent flipping of substrates, after removing the PCD rim and polishing the grown surface, it is possible to obtain high quality, large type IIa SCDs. The importance of laser cutting the rim and polishing the surface after each step will be discussed.
References
[1] J. Asmussen, et.al. US Pat. 8,316,797 (2012)
[2] J. Asmussen, J. Lu, Y. Gu, & S. Nad, US Prov. Pat. (filed May 23, 2014)
[3] I. Friel et.al. Diam. & Rel. Mat. 18 (2009) 808-815
9:00 AM - R3.15
Deposition of CVD Diamond onto Zirconium
Fiona Brannan 1 Paul William May 1 Sarah Halliwell 1
1University of Bristol Bristol United Kingdom
Show AbstractZirconium alloys are used to make the hollow tubular fuel rods which hold the nuclear fuel in nuclear reactors. However at high temperatures it can react with the water and corrode, releasing hydrogen as a by-product. Under exceptional circumstances (e.g. a meltdown event such as happened at Fukushima) enough hydrogen can be released that an explosion occurs, with potentially catastrophic results.
One possible solution to this is to coat the Zr with a layer of diamond to prevent the hot Zr coming into direct contact with water. Diamond is an ideal material for this as its high thermal conductivity will help transfer heat from the fuel-rods into the water efficiently, while it&’s low atomic number means that it will not absorb neutrons and affect the nuclear reaction. Diamond is also mechanically robust and radiation hard.
However, little has been reported yet about the growth of CVD diamond onto Zr or Zr-alloys. As such, we have studied the deposition of CVD diamond onto flat samples of pure Zr using various CVD growth conditions in a hot filament reactor. We find that although growth is straightforward, adhesion of the diamond layer onto the Zr is poor, with the diamond layer often delaminating upon cooling. SIMS depth profiles show this to be due to the presence of a strongly-bonded native oxide on the Zr surface which is not removed in the reducing H2 atmosphere during CVD. This, plus the lack of any carbide interfacial layer to ‘glue&’ the diamond onto the surface, together with a poor thermal expansion mismatch between Zr and diamond, all lead to poor adhesion. Some of these difficulties can be reduced by depositing at lower temperature (<500°C) at the cost of poorer quality diamond.
9:00 AM - R3.16
Fabrication of Heterojunction Diodes Comprising Nitrogen-Doped Ultrananocrystalline Diamond/Amorphous Carbon and p-Type Silicon
Abdelrahman Zkria Ahmed 1 2 Hiroki Gima 1 Shaban Mahmoud 3 Tsuyoshi Yoshitake 1
1Kyushu Univ Kasuga Japan2Aswan University Aswan Egypt3Aswan University Aswan Egypt
Show AbstractUltrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films have a specific structure, wherein a large number of diamond nanograins are embedded in an a-C:H matrix, It has been demonstrated that their p- and n-type conduction accompanied by enhanced electrical conductivity are possible by boron and nitrogen doping, respectively.1,2) . In this study, heterojunction diodes comprising nitrogen-doped UNCD/a-C:H and p-type Si were fabricated by coaxial arc plasma deposition (CAPD) and their electrical properties were investigated at room temperature. Experimentally, 3.55 at.% nitrogen-doped UNCD/a-C:H films were deposited on p-type Si (100) substrates with an electrical resistivity of 10-20 Omega; cm by CAPD. Radio Frequency (RF) sputtering was employed to deposit Pd ohmic electrodes on both sides of the samples. The current-voltage (I-V) characteristics of the diodes were measured in the dark at room temperature. The I-V curve exhibited a rectifying action with a recti#64257;cation ratio between bias voltages of ± 5 V of more than 104, which proves that the nitrogen-doped UNCD/a-C:H evidently acts as a n-type semiconductor. Capacitance-voltage (C-V) measurements were applied to study the nature of depletion regions in the diodes. The frequency and testing signal for measuring the capacitance was 100 kHz and 50 mV, respectively. The capacitance decreased with increasing reverse voltage, which evidently indicates the expansion of the depletion region with the reverse bias. The built in potential was estimated to be 0.68 V from the intercept of the plot of 1/C2 versus V (with the x-axis). Moreover, by using known physical values such as the carrier concentration of the n-type Si substrate being 5 x 1015 cm-3, the active carrier concentration of the UNCD/a-C:H #64257;lm was estimated to be 6.0 x1015 cm-3. It was experimentally demonstrated that the heterojunctions comprising nitrogen-doped UNCD/a-C:H work as typical diodes and nitrogen-doped UNCD/a-C:H is applicable to electrical devices as a n-type semiconductor.
[1] S. Ohmagari et al., JJAP 51, 090123 (2012). [2] S. Al-Riyami et al., APEX 49, 115102 (2010).
9:00 AM - R3.17
Isotopically-Engineered High Purity Diamond Film Growth
Tokuyuki Teraji 1
1National Institute for Materials Science Tsukuba Japan
Show AbstractColor centers in diamond, such as nitrogen-vacancy (NV) centers, are intensively studied for realizing high-performance devices utilizing these unique spin properties. In order to make these centers single photon sources, their concentration should be controlled in the range of <1013 cm-3 (<0.1 ppb). This concentration is at least two orders of magnitude less than the minimum donor/acceptor concentration required for electric conduction control. Synthesis of such high chemical purity diamond is one of the challenging topics for diamond chemical vapor deposition (CVD). Carbon isotopic control is another demand together with improving crystalline quality for controlling nuclear spin density in diamond and/or increasing the spin coherent time.
In this study, 12C isotopically-enriched homoepitaxial diamond films were deposited on Ib(100) or IIa(100) single crystals by a home-built microwave plasma-assisted CVD. Oxygen was fed with rather high concentration of 2% toward total flow to inhibiting crystalline defect formation during growth. By employing this condition, rather thick (~20 mu;m) homoepitaxial layers were grown with better surface flatness (Ra <10 nm).
The highest 12C enrichment of 99.998% among the previous reports was achieved. Nitrogen concentration of the homoepitaxial diamond films was less than 1 ppb. No NV0/- and SiV- centers were detected from as-grown homoepitaxial films by using cathodeluminescence and confocal photoluminescence set-up. Single NV0/- and SiV- were, then, successfully created by introducing nitrogen or silicon source during growth.
9:00 AM - R3.18
Analysis of Single Crystal Synthetic Diamond
Jafar F. Al-Sharab 1 Robert Horvath 1 Stephen D Tse 2 Bernard H Kear 1
1Rutgers University Piscataway USA2Rutgers University Piscataway USA
Show AbstractSynthetic diamond powder is synthesized by a high pressure/high temperature method. SEM analysis shows that the diamond powder (45 µm particle size) is composed of single crystals, with well-defined cubo-octahedral faceting. On the other hand, XRD analysis displays a single crystal pattern with a high degree of peak broadening, as well as a broad low-angle peak, clearly indicating a high level of lattice defects in the crystalline material. EELS analysis confirms that the powder is composed of high purity carbon. A small sample of the diamond powder is crushed and ground into much finer particles, such that a few tapered edges are suitable for high resolution TEM. SAD analysis confirms the XRD results, indicating areas of well-defined crystallinity, associated with regions of no resolved crystallinity. A typical SAD pattern shows crystalline spots superimposed on broad diffraction rings. Dark-field imaging of the non-crystalline regions indicates the presence of a second phase or lattice disorder. No dislocations are observed in the lattice-fringe patterns. The measured lattice constants verify the diamond-cubic structure. The current work quantifies defect density from EELS, XRD, and SAD.
R1: Nanodiamond and Surface Modification
Session Chairs
Chia-Liang Cheng
Robert Hamers
Monday AM, December 01, 2014
Hynes, Level 3, Room 303
9:45 AM - *R1.01
Functionalized Nanodiamond as a Non-Reactive Probe of Nanoparticle Interactions in the Environment
Robert Hamers 1 Marco Torelli 1 Arielle Mensch 1 Joel Pedersen 1 Thomas Kuech 1 Eric Melby 1 Rebecca D. Klaper 7 Jared Bozich 7 Gustavo Dominguez 7 Christy L. Haynes 2 Ian Gunsolus 2 Galya Orr 5 Laura Olenick 4 Julianne Troiano 4 Franz M. Geiger 4 Catherine J. Murphy 3 Min Yan 6
1University of Wisconsin Madison USA2University of Minnesota Minneapolis USA3University of Illinois Urbana USA4Northwestern University Evanston USA5Pacific Northwest National Laboratory Richland USA6Thermo-Fisher Scientific Verona USA7University of Wisconsin-Milwaukee Milwaukee USA
Show AbstractThe recent growth in the technological applications of nanoparticles is fueling increased interest in understanding how nanoparticles interact with with the environment, including interactions with single- and multi-cellular organisms. Nanodiamond is of particular interest because the ability to functionalize the surface with a range of ligands in an ultra-stable manner provides a mechanism for understanding how properties such as surface charge impact the resulting biological response. We developed nanodiamond particles functionalized with different ligands and examined their interaction with supported lipid bilayers and with two model organisms: Shewanella oneidensis (a soil bacterium) and Daphnia magna (the water flea). A comparison of identically functionalized 4-nm nanodiamond and ~4-nm nano-gold shows significant differences in the biological response and in their interaction with supported lipid bilayers. Our results highlight that even with functionalized nanoparticles where the primary interactions are witih the exterior ligands, the composition and nature of the nanoparticle core still have a large effect. In this talk I will discuss some of the reasons behind these effects and the implications for understanding how nanodiamond and other nanoparticles impact the environment.
10:15 AM - R1.02
Integrated Nanocrystalline Diamond Heater and Temperature Sensing Platform
Tim Clukers 1 Sien Drijkoningen 1 Patrick Wagner 1 2 Michael Daenen 1 Ken Haenen 1 2
1Hasselt University Diepenbeek Belgium2IMEC vzw. Hasselt Belgium
Show AbstractIn recent years there has been a leap forward in the number of applications and methods to read out and measure biological markers [1,2]. Depending on the envisaged application, different materials are used for the sensor platform. In this work, an integrated diamond based temperature sensor is presented, simultaneously acting as a DNA immobilization platform capable to detect single nucleotide polymorphisms through the in-house developed heat-transfer resistance method [1]. The different fabrication steps will be discussed in detail, complemented with finite-element modelling describing the expected thermal behaviour.
To ensure reproducible high quality measurements a well delineated number of steps are required assuring a T-sensor capable of reaching an accuracy of 0,1°C. A Corning Eagle-glass substrate is overgrown with a thick heavily boron-doped nanocrystalline diamond (B-NCD) layer. After a seeding step, using a colloidal solution of ultra-dispersed nanodiamond, the growth is done in an ASTeX 6500 microwave plasma enhanced chemical vapour deposition reactor using 4 % methane with respect to hydrogen, ± 8330 ppm trimethyl boron-to-methane at an overall deposition temperature of ± 560°C. Subsequently, the layers are patterned using photo-lithography to form a double interdigital meandering structure that will form the base for both the heating and the sensing structure of the temperature sensor. To ensure a wide range of resistance values of the meandering structures, this being a key factor for the steering of the sensor, 9 different structures were designed. Once the developed patterns are imprinted on top of the B-NCD-layer, an O2-plasma etching step assured selective removal of part of the B-NCD, leaving the described meander structures, which show a total resistance ranging from 0,7 k#8486; for the simplest and widest structure to 40 k#8486; for the finest and more complicated structures. To assure heat conduction through the complete structure whilst retaining electrical separation between the two interdigitated B-NCD meanders a thin layer of undoped NCD is selectively deposited on top using AlN as a local mask during the reseeding [3].
Finally, the thermal behaviour of the design is modelled using COMSOL Multiphysics, analysing the possible existence of hotspots on the sensor surface, experimentally verified through the use of thermal imaging.
[1] B. van Grinsven, et al., ACS Nano 6(3) 2712-2721 (2012)
[2] M. Peeters, et al., Analytical and Bioanalytical Chemistry 405(20) 6453-6460 (2013)
[3] P. Pobedinskas, et al., Applied Physics Letters 102 201609 (2013)
10:30 AM - R1.03
Spectroelectrochemistry of Nitrogen Vacancy Centers in Nanodiamonds
Sinan Karaveli 1 2 Reyu Sakakibara 1 Abraham Wolcott 1 2 3 Darcy S. Peterka 4 Jonathan S. Owen 3 Ophir Gaathon 5 Rafael Yuste 4 Dirk R. Englund 1
1Massachusetts Institute of Technology Cambridge USA2Columbia University New York USA3Columbia University New York USA4Columbia University New York USA5Diamond Nanotechnologies, Inc. Boston USA
Show AbstractThe negatively charged Nitrogen-Vacancy (NV) center in diamond is a versatile quantum emitter that can be used for various quantum information and sensing applications. However, it has been shown that a NV center can randomly switch between its negative and neutral charge states, with the latter not exhibiting the optical and spin properties desired for many applications. Despite recent advances, the factors affecting the charge state stability, especially for NV centers in nanodiamonds, are not well understood. Here, we present spectroelectrochemical studies of single NV centers in high-pressure high-temperature (HPHT) nanodiamonds. Specifically, we deposit nanodiamonds on an indium-tin-oxide (ITO) coated coverslip, which functions as the working electrode of an electrochemical cell. The transparent ITO layer allows for the continuous excitation and monitoring of the NV fluorescence as a function of the voltage applied between the ITO electrode and an aqueous electrolyte. Wide-field microscopy measurements show that a high fraction of the NV centers exhibits voltage-controllable fluorescence intensity. Spectral and time-resolved measurements confirm that the applied voltage alters the NV charge state and fluorescence dynamics. We discuss models for the physical origin of the observed voltage-dependent fluorescence intensity. In addition to charge state control of NVs for quantum applications, these results indicate that NV centers in nanodiamonds could be used as optical sensors of local electric fields and voltages. Specifically, we demonstrate that the NV fluorescence can be used to detect 100 mV potential increases using wide-field microscopy and 10 ms voltage pulses using confocal detection, illustrating the potential of NV centers as fluorescent voltage indicators.
10:45 AM - R1.04
Patterned Graphene Growth on Diamond - A Solid State Approach
Andrew Evans 1 Simon Cooil 1 Yuran Niu 2 Alexei Zhakharov 2 Marco Bianchi 3 Justin Wells 4 Philip Hofmann 3
1Aberystwyth University Aberystwyth United Kingdom2Lund University Lund Sweden3Aarhus University Aarhus Denmark4Norwegian University of Science and Technology Trondheim Norway
Show AbstractThe growth of ordered graphene films on metalized diamond at reduced temperatures has been previously demonstrated[1]. The focus to date has been on the epitaxial diamond (111)/Fe interface, however recent studies have also confirmed the growth of graphene on the more industrially common diamond (001) substrates. Synchrotron radiation techniques such as photoelectron spectroscopy/microscopy (PES)/(PEEM), as well as electron illumination techniques such as low energy electron diffraction (LEED) and low energy electron microscopy (LEEM) have been used to study the growth, structure and morphology of the sample. The process has been investigated from the deposition of a thin catalyst layer, through to the growth of graphene, in situ and in real-time. The ability to laterally resolve the surface has led to further progress in patterning the catalyst on defined regions of the surface and subsequent graphene growth. Graphene areas as small 10 mu;m2 were fabricated, enabling the ability to produce patterned graphene electronic devices.
1. Cooil, S.P., F. Song, G.T. Williams, O.R. Roberts, D.P. Langstaff, B. Joslash;rgensen, K. Hoslash;ydalsvik, D.W. Breiby, E. Wahlström, D.A. Evans, and J.W. Wells, Iron-mediated growth of epitaxial graphene on SiC and diamond. Carbon, 2012. 50(14): p. 5099-5105.
11:30 AM - *R1.05
Brilliant Nanodiamond Particles
Olga Shenderova 1 2 Gary McGuire 1 2 Igor Vlasov 3 Jessica Rosenholm 4
1ITC Raleigh USA2Adamp;#225;mas Nanotechnologies, Inc Raleigh USA3General Physics Institute Moscow Russian Federation4Abo Akademi University Turku Finland
Show AbstractDespite that nanodiamond (ND) particles were discovered more than 50 years ago and experienced mass production in the early 80s, for a long time they were in the shadow of their more famous sp2 carbon cousins. Two recent major breakthroughs, the production of individual nanodiamond particles 4-5nm in size and nanodiamond particles containing colour centres exhibiting stable luminescence and unique spin properties have brought ND particles to the forefront of materials research and applications.1 Besides well-known outstanding mechanical and thermal properties diamond particles have remarkable optical properties in combination with biocompatibility, high specific surface area, and tuneable surface structure.
The optical emission, scattering and attenuation of ND are finding unique applications in a variety of fields. In life science nanoparticles are increasingly used as fluorescent probes to monitor cellular interactions and to study cellular dynamics at the single molecular level. In one approach foreign atoms can be incorporated into the lattice of ND particles providing perfectly photostable particles as well as systems for quantum sensing applications that might be used to probe the nanoscale intracellular environment of cells. Development of multimodal imaging probes based on 5-10nm ND and doping of ND with different elements to generate photoluminescence at alternative wavelengths are future directions for this field. Carbon dot-decorated ND is an alternative means of generating photoluminescent nanoparticles with tuneable emission over the visible portion of the electromagnetic spectrum and into the near-infrared region.2 The photoluminescent ND is increasingly being viewed as a means of drug delivery. Encapsulating the ND in a porous silica shell will be discussed as a means to achieve stable fluorescent imaging with high loading capacity of bioactive molecules.3
Challenges related to the large scale production of ND containing colour centres as well as material characterization and standardization toward development of a commercial product will be also discussed.
1V.N. Mochalin, O. Shenderova, D. Ho, Y. Gogotsi, Nature Nanotechnology. 7 (2012) 11-23.
2O. Shenderova, S. Hens, I.I. Vlasov, S. Turner, Y.-G. Lu, G. Van Tendeloo, A. Schrand, S. Burikov, T. Dolenko, Particle & Particle Systems Characterization, 2014; 31(5): 580-590
3E. Von Haartman, H. Jiang, A. Khomich, Shenderova O. et al. , J. Mater. Chemistry B, 1, (2013) 2358-2366
12:00 PM - *R1.06
Surface Chemistry, Functionalization, and Their Effects on Adsorption of Molecules on Nanodiamond
Vadym N. Mochalin 1 James Giammarco 1 Yury Gogotsi 1
1Drexel University Philadelphia USA
Show AbstractDiamond particles smaller than 10 nm (ND) have remarkable physical properties in combination with biocompatibility, high specific surface area, and tunable surface chemistry [1]. They are the least toxic of all carbon nanoparticles and their properties make them a favorable platform for drug delivery, cellular labeling/imaging, composites, lubricants and many other applications. However, to harness the potential of ND in all those applications, purification, characterization, particle size control and functionalization of the diamond surface is needed. We have demonstrated control of nanodiamond surface chemistry by using various dry and wet chemical methods in order to improve its dispersion stability in solvents and polymers, as well as control its adsorption capacity and strength of adsorption. For example, we have also shown that decoupling of the oxidation reaction into the oxygen chemisorption and the CO and/or COx desorption steps allows layer-by layer oxidation of nanodiamond [2], which can be used to control ND particle size, as well as its surface chemistry . The diamond nanoparticles showed a continuous size decrease and increase in the specific surface area during layer-by-layer oxidation cycles, while simple oxidation in air leads to burn-off of the smallest ND particles and an increase in the average particle size. We show on an example of several drugs that various surface modifications allow control of the amount of drug adsorbed and the strength of adsorption.
References
V. Mochalin, O. Shenderova, D. Ho, Y. Gogotsi, The properties and applications of nanodiamonds, Nature Nanotechnology,7 (1) 11-23 (2012)
B.J.M. Etzold, I. Neitzel, M. Kett, F. Strobl, V.N. Mochalin, Y. Gogotsi, Layer-by-Layer oxidation for decreasing the size of detonation nanodiamond, Chemistry of Materials, 26, 3479-3484 (2014)
V. N. Mochalin, A. Pentecost, X.-M. Li, I. Neitzel, M. Nelson, C. Wei, T. He, F. Guo, Y. Gogotsi, Adsorption of Drugs on Nanodiamond: Towards Development of a Drug Delivery Platform, Molecular Pharmaceutics, 10 (10), 3728-3735 (2013)
12:30 PM - R1.07
Diamond Surface Characterisation Using Parallel Real-Time XPS and Stand-Off Raman Spectroscopy
Simon Cooil 1 Gruffudd Williams 2 Rachel Cross 1 Andrew Evans 1
1Aberystwyth University Aberystwyth United Kingdom2Element Six Ltd Harwell United Kingdom
Show AbstractThe electrical conductivity and chemical reactivity of diamond surfaces are controlled by surface processing using high temperature annealing and metalization. Parallel, real-time X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy has been applied to the processing of low index faces of semiconducting diamond in a controlled vacuum environment. Annealing of the diamond (111) and diamond (001) surfaces to 1200 K while monitoring using electrons and photons reveals correlations between surface composition and surface conductivity with high temperature accuracy. Metalization using ultrathin Ag and Fe overlayers modifies the surface termination, changes the conductivity and enhances the surface light scattering.
12:45 PM - R1.08
Chemo-Mechanical Polishing of Diamond
Evan LH Thomas 1 Soumen Mandal 1 Emmanuel Brousseau 2 Geoffrey Nelson 3 John S Foord 4 Oliver Aneurin Williams 1
1Cardiff University Cardiff United Kingdom2Cardiff University Cardiff United Kingdom3Imperial College London United Kingdom4University of Oxford Oxford United Kingdom
Show AbstractNanocrystalline Diamond (NCD) has many extreme properties making it attractive for use in applications from Micro-Electro-Mechanical Systems (MEMS) to thermal management. The unrivalled Young&’s modulus (>1100 GPa) and thermal conductivity (2000 W/mK) as well as the possibility of integration with CMOS and III-V heterostructures have bolstered significant research efforts in the growth and applications of NCD films.
However, NCD films have a roughness that evolvesinvolves with films thickness, which can adversely affect its integration into multi-layered devices where a smooth surface is important. In order to reduce this roughness the technique of Chemical Mechanical Polishing (CMP), commonly used for polishing of dielectrics and metal interconnects in the semiconductor industry, has been applied to the polishing of NCD films. This technique is important as it is able to compensate for wafer bow which is significantly greater than the film thickness.
NCD films were grown under low methane / high power density conditions in order to realisze optimiszed diamond properties. These films were then polished with a Logitech Tribo CMP tool, using polyurethane impregnated polyester felts doused with alkaline colloidal silica (SytonTM) and characterisesied after various durations. The surface roughness was characterised over 5 x 5 µm area with Atomic Force Microscopy and the morphology with Scanning Electron Microscopy. The surface roughness was reduced from 20 nm RMS (for as grown films) to below 2 nm RMS (over 5x5 µm2) [1].
Finally, the polishing of (111) and (100) single crystal diamond surfaces will be demonstrated. A reduction in roughness from 0.92 to 0.23 nm RMS and 0.31 to 0.09 nm RMS for (100) and (111) samples respectively was observed.
1. Thomas, E.L.H., et al., Chemical mechanical polishing of thin film diamond. Carbon, 2014. 68(0): p. 473-479.