IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Semiconductors Thursday Sessions
       Session SC+SS+EL-ThM

Paper SC+SS+EL-ThM9
Are Silicon and Germanium Surfaces Chemically Similar? Reactions of Amines

Thursday, November 1, 2001, 11:00 am, Room 111

Session: Interaction of Hydrogen and Organics with Silicon
Presenter: C. Mui, Stanford University
Authors: C. Mui, Stanford University
G.T. Wang, Stanford University
J.H. Han, Stanford University
C.B. Musgrave, Stanford University
S.F. Bent, Stanford University
Correspondent: Click to Email
The organic chemistry at silicon and germanium surfaces has been studied in the past, and the chemical similarity between the two materials is often exploited. In this study, we will present an example in which the surface chemistry of silicon and germanium are notably different. We have used surface infrared spectroscopy and temperature programmed desorption to investigate the chemistry of amines at the Si(100)-2x1 and the Ge(100)-2x1 surfaces. We find that surface reaction of methylamine and dimethylamine on the Si(100)-2x1 surface results in facile N-H dissociation, whereas molecular adsorption occurs on the Ge(100)-2x1 surface. We also show that molecular adsorption of amines on both the Si(100)-2x1 and the Ge(100)-2x1 surfaces occurs through the formation of surface dative bonds which are stable at room temperature. Quantum chemistry calculations are used to explain the observed reactivity difference between the two surfaces. We find that N-H dissociation of dimethylamine is kinetically favored compared to N-CH3 cleavage on both surfaces. However, while N-H dissociation on the Si(100)-2x1 surface is unactivated, the overall activation energy for N-H cleavage on the Ge(100)-2x1 surface is above the vacuum level, explaining the lack of reactivity on the Ge(100)-2x1 surface. We will also discuss our theoretical approach for modeling reactions at semiconductor surfaces, including the effect of surface cluster models and basis sets.