This is a new symposium for the MRS Spring Meeting. The last few years have seen very strong development in the field of in situ, in operando techniques and the extension of traditionally in vacuum materials characterization methods to sample environments that are extremely relevant for important research fields such as catalysis. This tutorial will highlight recent developments in this area.
1:30 pm – 3:00 pm
Part I: Jolien Dendooven
In Situ Characterization of Atomic Layer Deposition Processes
Atomic layer deposition (ALD) is a self-limited growth method which relies on sequential reactions of gas phase precursor molecules with a solid surface to deposit oxides, metals and other materials in a layer-by-layer fashion. The technique enables thickness control at the sub-nanometer level and conformal deposition on high aspect ratio structures. While these advantages have rendered ALD a mainstream technique in microelectronics, ALD is also being investigated for applications in catalysis, gas separation, sensors, batteries, capacitors, fuel cells, photovoltaics and photonics.
When exploring ALD processes, in situ characterization techniques offer the advantage that the ALD process no longer occurs in a “black box,” but that the surface chemistry and the properties of the growing film can be monitored in real time. Over the past decade, a variety of in situ techniques have been developed, and several have become available on commercial ALD reactors.
Following a brief introduction to ALD, this tutorial aims at giving an overview of in situ methods used in current ALD research. The advantages of using in situ techniques to determine ALD growth characteristics will be discussed, and examples of quartz crystal microbalance, quadrupole mass spectroscopy, spectroscopic ellipsometry, Fourier transform infrared spectroscopy and optical emission spectroscopy will be provided. Next, the use of a variety of x-ray based diffraction, reflection, scattering and absorption techniques for in situ monitoring during ALD growth will be discussed. As will be demonstrated by several examples, the high photon flux at synchrotron facilities is beneficial during these experiments, as it lowers the acquisition times and enhances the detection limit, enabling the study of layer growth from the very first ALD cycle.
3:00 pm – 3:30 pm BREAK
3:30 pm – 5:00 pm
Part II: François Rochet
Real Time X-Ray Photoelectron Spectroscopy
X-ray photoelectron spectroscopy (XPS) is a powerful technique for determining the electronic structure and chemistry of surfaces, interfaces and nano-objects. Recent instrumental advances have made it possible to extend the scope of this spectroscopy to time-dependent phenomena, encompassing various timescales, from the in situ monitoring of chemical reactions to pump-probe experiments such as photovoltage spectroscopy. The present tutorial aims at giving examples of such innovative applications. The outline of the tutorial is the following:
1. XPS in a nutshell. The principles of photoemission. What kind of information can be retrieved?
2. Ambient pressure XPS. The recent technical breakthroughs that make possible the in situ study of chemical reactions on a surface, with a vision of both the gas and condensed phase, in the mbar range and above.
3. Chemically resolved XPS in the ms range: a boon for kinetics studies.
4. Band bending at semiconductor surfaces/interfaces, chemical and physical consequences and why time matters.
- Jolien Dendooven, Ghent University
- François Rochet, Université Pierre et Marie Curie