Stacey F. Bent, Stanford University, Dept of Chemical Engineering, Stanford, CA 94305
Recent studies of the covalent attachment of organic molecules at group-IV (100)-2x1 semiconductor surfaces reveal that even for simple compounds, complex pathways and bonding geometries are common. To understand the factors that lead to such chemistry as well as to establish an integrated theory of bonding on these surfaces, a series of carbonyl-containing molecules were investigated on Ge(100)-2x1. The reactions of formaldehyde, acetic acid, acetyl chloride, formamide and their derivatives were studied with multiple internal reflection infrared spectroscopy, X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory. Several common themes in the adsorption chemistry of these carbonyl compounds are observed. Formation of dative-bonded precursor states occurs via donation from the carbonyl oxygen, subsequently leading to a variety of surface adducts which depend on the substituent attached to the carbonyl functionality. A bidentate bridging structure, where two heteroatoms from the molecule interact directly with the surface, was identified for several of the molecules. Results will be discussed within the context of classical organic chemistry.