ELECTRON-INDUCED SURFACE-CHEMISTRY - SYNTHESIS OF NHX FRAGMENTS ON AG(111)

Electron-induced decomposition of chemisorbed NH3, dosed on Ag(lll), a t 115 K has been studied using x-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). There is no thermally act ivated dissociation during dosing or TPD. The N(ls) XPS peak is at 400 .1 eV binding energy (BE) and, in TPD, there is a sharp peak at 130 K with a trailing edge toward higher temperatures. Following low energy (50 eV) electron irradiation the 130 K TPD peak area drops sharply whi le the XPS N(ls) peak area drops much less. This indicates that, while some N-containing species are ejected during electron irradiation, mo st of the initial N is retained in some form. After irradiating with 5 x10(16)e cm(-2) the N(1s) BE shifts lower and the peak can be fit with two peaks, one corresponding to residual NH3, and a second to NH2 (39 8.9-399.1 eV BE). Increasing the fluence to 1x10(17) e cm(-2), shifts the N(ls) profile to even lower BE; two peaks assigned to NH2 and NH ( 398.1 eV BE) give an acceptable fit. (C) 1996 American Vacuum Society.