ELECTRON-STIMULATED DESORPTION TOTAL CROSS-SECTION DETERMINATION FOR DIGERMANE ON SI(100)

We have studied digermane-covered Si(100) using electron-stimulated de sorption (ESD). Estimates are presented for the total H(a) ESD removal cross-section for digermane-exposed Si(100) substrates at 85 K using electrons incident at 150 eV energy, It is found that electron-enhance d deposition of Ge occurs only when physisorbed digermane is present. Auger electron spectroscopy provided the means for determining the rel ative amounts of germanium adsorbed on the Si(100) surface following d igermane exposures, electron irradiation and surface reconstruction, I t is found that two coverage regimes are important: initial dosing of digermane on Si(100) at 85 K results in overlayers consisting of both physisorbed digermane and chemisorbed GeHx(a) (x = 1, 2 or 3) species; and short anneals to 200 K following exposure of the Si(100) surface at 85 K lead to the presence of only chemisorbed GeHx(a). The two cove rage regimes exhibit different ESD behavior. Two kinetic energy distri bution (KED) peaks are seen when physisorbed digermane is present, and only one when it is absent, The ESD signal decay curves obtained from the two surfaces are also different: the presence of physisorbed dige rmane results in a two-component exponential signal decay; the absence of the physisorbed species results in a single-exponential decay. The total H removal cross-section from the physisorbed digermane overlaye r was determined to be sigma similar to 1.4 x 10(-15) cm(2), while tha t from Si(100) with only adsorbed GeHx present was found to be sigma s imilar to 2.6 x 10(-16) cm(2). Our results suggest that adsorbed GeHx( a) species remain intact on the surface even when the Si(100) substrat e is annealed to 200 K, indicating that hydrogen migration from surfac e GeHx(a) to Si surface sites does not occur at 200 K. (C) 1998 John W iley & Sons, Ltd.