AVS 52nd International Symposium
    Surface Science Thursday Sessions
       Session SS2-ThM

Paper SS2-ThM3
Amide Chemistry at the Ge(100)-2x1 Interface

Thursday, November 3, 2005, 9:00 am, Room 202

Session: Functionalization of Semiconductor Surfaces
Presenter: A.J. Keung, Stanford University
Authors: A.J. Keung, Stanford University
M.A. Filler, Stanford University
S.F. Bent, Stanford University
Correspondent: Click to Email
Organic functionalization of semiconductor surfaces has many potential applications including semiconductor processing, molecular electronics, and chemical sensors. In particular, understanding the surface reactivity of the amide linkage could be important in developing biologically-based devices. In situ vibrational spectra were obtained as a function of coverage, temperature, and time for a series of primary, secondary, and tertiary amides absorbed on the Ge(100)-2x1 surface under ultrahigh vacuum conditions. For the tertiary amides, including dimethyl formamide, 1-methyl-2-pyrrolidinone, and n,n-dimethyl acetamide, asymmetric and symmetric N-C-O stretching, aldehydic C-H bending, as well as methyl deformation modes were observed, while Ge-H stretching modes were absent. This data provides evidence that tertiary amides form a dative-bond between the carbonyl oxygen and the electrophilic germanium dimer atom. Theoretical spectra of dative-bonded structures, calculated with density functional theory, agree well with experiment. In addition, these products desorbed at 310K on the timescale of minutes suggesting dative-bonded tertiary amides are just at the cusp of stability on Ge(100)-2x1. The primary and secondary amides, formamide and n-methyl formamide, respectively, were also investigated. Two types of products were observed for each compound at room temperature. Comparison to the experimental spectra of dimethyl formamide provides evidence for dative-bonded products. Dissociation products were also formed as evidenced by the growth of Ge-H stretches. The dissociation products were favored at higher temperatures, and there is evidence for dative-bonded adducts converting to these products upon annealing. Due to a kinetic barrier to this reaction, the dative-bonded state can be isolated at low temperature. These results have implications for understanding the reactivity of larger biological molecules such as peptides.