Electron-stimulated dissociation of ammonia adsorbed on Ge(100)

Electron-stimulated dissociation of adsorbed ammonia on Ge(100) at 110 K was studied using temperature-programmed desorption (TPD), electron-stimulated desorption, and X-ray photoelectron spectroscopy (XPS). Electron-induced dissociation and nitridation of the Si(100) surface using ammonia as a precursor has been extensively explored recently in our laboratory. Since Ge(100) exhibits the same (2 x 1) reconstruction as does Si(100), we have initiated studies to determine whether this similarity extends to germanium nitride formation stimulated by low energy electron irradiation. TPD spectra over a wide coverage range are shown indicating presence of several types of states denoted by alpha, beta, and gamma, depending upon the exposure range. No evidence was found for dissociation of ammonia upon adsorption regardless of the coverage. XPS studies of binding energy changes associated with both the N 1s and Ge 2p(3/2) states will be presented resulting from electron irradiation of adsorbed ammonia, which indicates formation of germanium nitride. Time-of-flight spectra of desorbing H+ will also be shown over a wide range of coverages. A recently observed phenomenon characterized as electron-stimulated associative desorption will also be discussed in which irradiation of a condensed layer of ammonia results in desorption of neutral H-2 and N-2 as well as several molecular ions. (C) 2000 Elsevier Science B.V. All rights reserved.