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

Electron-stimulated dissociation of adsorbed ammonia on Ge(100) at 110 K wa s studied using temperature-programmed desorption (TPD), electron-stimulate d desorption, and X-ray photoelectron spectroscopy (XPS). Electron-induced dissociation and nitridation of the Si(100) surface using ammonia as a prec ursor has been extensively explored recently in our laboratory. Since Ge(10 0) exhibits the same (2 x 1) reconstruction as does Si(100), we have initia ted studies to determine whether this similarity extends to germanium nitri de formation stimulated by low energy electron irradiation. TPD spectra ove r a wide coverage range are shown indicating presence of several types of s tates denoted by alpha, beta, and gamma, depending upon the exposure range. No evidence was found for dissociation of ammonia upon adsorption regardle ss of the coverage. XPS studies of binding energy changes associated with b oth the N 1s and Ge 2p(3/2) states will be presented resulting from electro n irradiation of adsorbed ammonia, which indicates formation of germanium n itride. Time-of-flight spectra of desorbing H+ will also be shown over a wi de range of coverages. A recently observed phenomenon characterized as elec tron-stimulated associative desorption will also be discussed in which irra diation 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.