Abstract
Adsorption of acetic acid on the Si (001)-(2X1) surface is studied by x-ray photoelectron spectroscopy (XPS), scanning-tunneling microscopy (STM), and ab initio calculations. We find that C 1s line of the acetic acid on the surface is composed of mainly methyl and adsorbed carboxyl groups. The filled-state STM images indicate that protrusions of the adsorbate are located on center of single Si dimer. The on-top configuration with a vertical Si-O-C(CH3)-O-Si linkage to the Si dimer is supported by these XPS and STM results. The ab initio calculations show a plausible reaction pathway from the initial adsorption structure with O-H cleavage to the on-top configuration.