SURFACE CHEMISTRY OF SEMICONDUCTORS AND OXIDES

A. Amorphous silica, metal oxides:

This project aims to: 1) develop a quantitative understanding of the surface structure and chemistry of amorphous silica (a-SiO₂) materials associated with point-like defects, surface charges, external stresses, and chemical additives, and 2) apply the mechanistic understanding toward development of a detailed model for the controlled synthesis of silica-supported semiconductor (silicon [Si]) and metal (gold[Au]) nanostructures which have various novel applications such as nanocrystal memories, optical interconnects, and microporous catalytic membranes for hydrogen purification. Atomic-level manipulation and accurate determination of the surface structure and function of amorphous oxides has long been an issue of great importance due to their many applications in electronics, optics, catalysis, and sensors. However, the difficulty of direct characterization has impeded progress towards understanding the complex nature of amorphous oxide surfaces. Recent significant advances in theoretical techniques and computing power now make it possible to explore chemical and physical phenomena occurring at the oxide surface at the atomic scale.

§ C.-L. Kuo, S. Lee and G.S. Hwang, “Strain-induced Formation of Surface Defects in Amorphous Silica: A Theoretical Prediction,” Phys. Rev. Lett. 100, 076104 (2008).

§ Kuo and G.S. Hwang, “Structure and Interconversion of Oxygen Vacancy Related Defects on Amorphous Silica,“ Phys. Rev. Lett. 97, 66101 (2006).

§ Pillay, Y. Wang, and G.S. Hwang, “Prediction of Tetraoxygen Formation on Rutile TiO₂(110),“ J. Am. Chem. Soc. 128, 14000 (2006).

§ Pillay and G.S. Hwang, “O₂-Coverage Dependent CO Oxidation on Reduced TiO₂(110): A First Principles Study,“ J. Chem. Phys. 125, 144706 (2006).

§ Y. Wang, D. Pillay and G. S. Hwang, “Dynamics of oxygen species on reduced TiO₂(110) rutile,” Phys. Rev. B, 70(4), 193410 (2004).

§ Y. Wang and G. S. Hwang, “Adsorption of Au atoms on stoichiometric and reduced TiO₂(110) rutile surfaces: a first principles study,” Surf. Sci. 542 (1-2), 72 (2003).

B. Group IV semiconductors:

This project intends to develop a detailed understanding of the interaction of organics with clean, defective, and modified semiconductor surfaces, which can in turn assist in finding new and reliable ways to synthesize desired organic structures on a semiconductor surface for future molecular devices. Imparting organic functions with atomic-scale precision onto well-defined semiconductor surfaces may provide an enormous opportunity to develop novel molecular devices including: chemical and biological sensors and molecular electronics.

§ M.C. Kim, G.S. Hwang, and R.S. Ruoff, “Epoxide Reduction by Hydrazine on Graphene: A First Principles Study,” J. Chem. Phys. 131, 064704 (2009).

§ Y. Wang and G. S. Hwang, “Origin of Non-local Interactions in Adsorption of Polar Molecules on Si(001)-2´1,” J. Chem. Phys. 122, 164706 (2005).

§ Y. Wang and G. S. Hwang, “P-Assisted Growth of Molecular Wires on Si(001)-2´1,” Appl. Phys. Lett. 86(2), 23108 (2005).

§ Y. Wang, S. Lee and G. S. Hwang, “Effect of Subsurface Boron and Phosphorus on the Surface Reactivity of Si(001),” J. Phys. Chem. B 108, 16147 (2004).

§ Y. Wang and G. S. Hwang^#, “Two Dimensional Arrangement of CH₃NH₂ Adsorption on Si(001)-2´1,” Chem. Phys. Lett. 385 (1-2), 144 (2004).

§ Y. Wang and G. S. Hwang^#, “Function of Subsurface Boron on Si (100)-2´1: Water Adsorption,” Surf. Sci. 547, L882 (2003).

§ Pillay, B. Steward, C. Shin and G. S. Hwang^#, “Revisit to an Ising Model for Order-Disorder Phase Transition on Si(001),” Surf. Sci. 554 (2-3), 150 (2004).