Si-H bond activation on Cu: Reaction of silane on Cu(111)

The activation and decomposition of silane on Cu(111) have been studied using Fourier transform infrared (FTIR), Auger electron (AES), and temperature-programmed reaction (TPRS) spectroscopies, as well as low-energy electron diffraction (LEED). Silane dissociatively chemisorbs on Cu(111) at 90 K. Cleavage of the Si-H bond yields two structurally distinct adsorbed silyl fragments. Infrared spectroscopy identifies the predominant intermediates formed under these conditions as being adsorbed SiH[sub 2] and SiH species. The relative and absolute concentrations of these intermediates depend sensitively on the surface coverage of both Si and H, which themselves depend upon the silane exposure. SiH[sub 2] is stable over a wide range of coverage up to 180 K, where it then undergoes Si-H bond cleavage to form surface bound SiH. At higher temperatures, bond scission in the Si-H moiety results in the formation of adsorbed silicon atoms and the desorption of dihydrogen in a peak centered at [approximately]330 K. Auger electron spectra show that the amount of silicon deposited on the Cu(111) surface in this way is approximately one-third of the amount deposited on a stable Cu[sub 3]Si surface. This latter surface is readily formed by carrying out the silane exposure at temperatures above 300 K. 39 refs., 15more » figs., 1 tab.« less