title: Proton transfer reactions on semiconductor surfaces.
abstract: The concept of proton affinity on semiconductor surfaces has been explored through an investigation of the chemistry of amines on the Ge(100)-2 x 1, Si(100)-2 x 1, and C(100)-2 x 1 surfaces. Multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy, temperature programmed desorption (TPD), and density functional theory (DFT) calculations were used in the studies. We find that methylamine, dimethylamine, and trimethylamine undergo molecular chemisorption on the Ge(100)-2 x 1 surface through the formation of Ge-N dative bonds. In contrast, primary and secondary amines react on the Si(100)-2 x 1 surface via N-H dissociation. Since N-H dissociation of amines at semiconductor surfaces mimics a proton-transfer reaction, the difference in chemical reactivities of the Ge(100)-2 x 1 and Si(100)-2 x 1 surfaces toward N-H dissociation can be interpreted as a decrease of proton affinity down a group in the periodic table. The trend in proton affinities of the two surfaces is explained in terms of thermodynamics and kinetics. Solid-state effects on the C(100)-2 x 1 surface and the surface proton affinity concept are discussed based on our theoretical predictions.
authors.affiliation: Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, USA.
authors.forename: Collin
authors.initials: C
authors.lastname: Mui
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Han
authors.forename: George T
authors.initials: GT
authors.lastname: Wang
authors.forename: Charles B
authors.initials: CB
authors.lastname: Musgrave
authors.forename: Stacey F
authors.initials: SF
authors.lastname: Bent