Yves J. ChabalProfessor of Materials Science & Engineering and Physics
Department Head, Materials Science & Engineering
Texas Instruments Distinguished University Chair in Nanoelectronics
Fellow of the AVS, American Physical Society, and Materials Research Society
1980-81 Postdoc, Surface Physics Department, Bell Labs
1980 PhD Physics, Cornell University
1974 AB Physics, Princeton University
2009 APS Davisson-Germer Prize
2012 ACS Award for Encouraging Women into Careers in Chemical Sciences
2012 AVS Medard W. Welch Award
Current interests are centered on surface chemical functionalization of semiconductor and oxide surfaces, atomic layer deposition, organic electronics, biosensors and H2 storage materials.
In our laboratory, we use (and in some cases develop) optical spectroscopic and imaging techniques to explore elementary processes at surfaces and interfaces of technologically important electronic, photonic, organic and more recently biological heterostructures. For instance, we have been leading the implementation of infrared absorption spectroscopy to develop a detailed mechanistic understanding of semiconductor surface cleaning (both by wet and dry techniques), passivation, and chemical functionalization. In particular, we have devised sensitive, in-situ methods to probe the interaction of chemical species with surfaces and the formation of thin dielectric films using a variety of methods based on wet chemistry, ultra-high vacuum (UHV) and vapor deposition. We are also probing the interaction of hydrogen in a variety of environments, most recently in storage materials for the hydrogen fuel economy. The work in our group has a direct impact on:
- Microelectronics, by identifying the surface modification after various wet chemical processes (HF etching, acid/base cleaning and etching) for several types of semiconductors (groups IV, IV-IV, III-V), by characterizing the nature of H, Cl, OH and oxide passivation of semiconductor surfaces, and by uncovering the growth mechanism of high-k dielectrics on silicon and germanium. We are exploring the growth by Atomic Layer Deposition (ALD) of Al2O3, HfO2, La2O3 with sub nm equivalent oxide thickness (to replace SiO2), and of metal contacts (TaN, Cu, Ru) and investigating the best wet chemical cleaning methods for high mobility substrates (e.g., Ge, InP) to replace silicon in future CMOS devices. We are also studying elementary processes at the surface of SiC, an important substrate for high-temperature, high-speed and high-voltage electronics.
- Optoelectronics, by providing chemical information and badly needed fundamental understanding of III-V semiconductor surface passivation. After studying wet chemical etching and oxidation of InP, we are now exploring gaseous oxidation in controlled environments (e.g., UHV).
- H2 storage for hydrogen fuel economy, by examining the manner in which hydrogen molecules interact and get incorporated into complex metal hydrides and metal organic framework (MOF) materials. In the case of metal hydrides, we study the dissociation and subsequent adsorption of H2 on Ti-doped aluminum surfaces to better understand and control the formation of complex metal hydrides (e.g., NaAlH4). For the MOF materials, we focus on the weak interactions between H2 molecules and the metal and organic ligands to design more effective ways of increasing the hydrogen concentration.
- Organic electronics, by characterizing the chemical and structural nature of self-assembled monolayers (SAMs) on both metal and semiconductor surfaces. We are focusing on providing chemical and structural information to understand electronic conduction in organic materials by paying special attention to contact issues (substrate/SAM interfaces and effects of depositing top metal electrodes on SAM films). We are also developing spectroscopic methods to study the dependence of electronic conduction on conformational changes within the SAMs.
- Nanoelectronics, by using biological approaches to patterning surfaces on the nm and sub-nm scale. For instance, the possibility to manipulate DNA scaffolding is used to meet tight nanolithography requirements of integrated nano-circuits. An important aspect of this work is the control of DNA bonding to semiconductor surfaces. To this end, we are working on the fundamentals of DNA/surface interactions.
- Biosensors and graphene, by understanding the interaction of biological macro-molecules (DNA, glucose, LDL, etc.) with both organic and inorganic substrates. For instance, by studying the modulation of the electric field and charge transfer mechanisms by biological molecules, we are devising ways to implement electronic detection of biological species. We are also studying the chemistry of graphite with aim to produce high-quality graphene (via graphene oxide) and to understand the oxidation of graphene using oxygen plasma, ozone and wet chemistry.
Our group is interdisciplinary in nature, with collaborations in physics, chemistry, materials science, chemical/biomedical/electrical engineering and even with UT Southwestern Medical Center. We have ongoing collaborations with National Laboratories (NIST, BNL, Sandia), with laboratories in Belgium, France, Germany, Italy, Korea and Japan, and with U.S. industries (TI, Qualcomm, Intel, SAFC Hitech, Air Products). We also have access to the National Synchrotron Light Source at Brookhaven Laboratory. Our goal is to develop the synergy necessary for substantial scientific advances in interfacial science and nanoelectronics, and to benefit in the process core U.S. industries and national initiatives of the Department of Energy.
Turning aluminium into a noble-metal-like catalystfor low-temperature activation of molecularhydrogen, I. S. Chopra, S. Chaudhuri, J. F. Veyan, and Y. J. Chabal, Nature Materials 10 (11), 884 (2011).
Nanopatterning Si(111) surfaces as a selective surface-chemistry route, D. J. Michalak, S. R. Amy, D. Aureau, M. Dai, A. Esteve, and Y. J. Chabal, Nature Materials 9 (3), 266 (2010).
Unusual infrared-absorption mechanism in thermally reduced graphene oxide, M. Acik, G. Lee, C. Mattevi, M. Chhowalla, K. Cho, and Y. J. Chabal, Nature Materials 9 (10), 840 (2010).
Nitrogen interaction with hydrogen-terminated silicon surfaces at the atomic scale, M. Dai, Y. Wang, J. Kwon, M. D. Halls, and Y. J. Chabal, Nature Materials 8 (10), 825 (2009).
Nanochemistry at the atomic scale revealed in hydrogen-induced semiconductor surface metallization, V. Derycke, P. G. Soukiassian, F. Amy, Y. J. Chabal, M. D. D'Angelo, H. B. Enriquez, and M. G. Silly, Nature Materials 2, 253 (2003).
Structural evolution during the reduction of chemically derived graphene oxide, A. Bagri, C. Mattevi, M. Acik, Y. J. Chabal, M. Chhowalla, and V. B. Shenoy, Nature Chemistry 2 (7), 581 (2010).
Room-temperature metastability of multilayer graphene oxide films, S. Kim, S. Zhou, Y. Hu, M. Acik, Y. J. Chabal, C. Berger, W. De Heer, A. Bongiorno, and E. Riedo, Nature Materials 11 (6), 544 (2012)..
Probing the catalytic activity of porous graphene oxide and the origin of this behaviour, C. Su, M. Acik, K. Takai, J. Lu, S. J. Hao, Y. Zheng, P. Wu, Q. Bao, T. Enoki, Y. J. Chabal, and K. P. Loh, Nature Communications 3, 2315 (2012).