Adsorption of partially and fully dissociatedH2Smolecules on the Si(001) and Ge(001) surfaces

Abstract

Ab initio calculations, based on pseudopotentials and the density functional theory, have been made to investigate the equilibrium atomic geometry, electronic states, and bonding of the H 2 S molecule on the Si͑001͒ and Ge͑001͒ surfaces within two dissociative adsorption geometries. First we consider adsorption of partially dissociated species (SH) Ϫ and H ϩ onto the Si or Ge dimer with a (1ϫ2) surface periodicity. Secondly, we consider adsorption of fully dissociated species S and 2H on the surface with a (1ϫ2) periodicity but without dimer formation. In general, the adsorption of H 2 S on the Si͑001͒ and Ge͑001͒ surfaces shows similar behavior. For both geometries studied here, the fundamental band gap is free of surface states, with the highest occupied state lying below the valence band maximum. ͓S0163-1829͑99͒14531-4͔

Ab initio surface reaction energetics of H2X (X=O or S) on Si(001)-(2×1)

“…1. Key structural parameters are presented in Table 1, where these are also compared with other works [1,[11][12][13]. In agreement with other works, we find that the adsorption of both the H 2 S and H 2 O molecules enlarges the original surface dimer length by approximately 4%, and that the dimer tilt is completely removed upon the partially dissociated molecular adsorption.…”

“…Using a simple argument based on the Arrhenius equation with a reasonable Table 1 Calculated values of the key structural parameters shown in Fig. 1 For comparison, also shown in parentheses are the results from other works: Slab-1 Ç akmak and Srivastava [1], 2 Seino and Schmidt [13], 3 Konečný and Doren [12] and 4 Cho et al [11].…”

“…With the on-going reduction in device size, the control of monolayer and submonolayer reactions is becoming more important to understand and control. The deposition of H 2 S upon Si(0 0 1)-(2 · 1) has been previously studied both theoretically [1] and experimentally [2]. Sulphur is known to be effective in electronically and chemically passivating semiconducting surfaces [3].…”

“…In this paper we present ab initio calculations of plausible reaction paths to the previously reported static structures [1,5] of H 2 X into the partial dissociation XH + H and the full dissociation X + H + H. For one fully dissociated structure the Si dimer is considered to be broken and each of the two Si dimer atoms is bonded symmetrically to both H and X. Another fully dissociated structure presented is also considered with an interstitially bonded X atom (X = O or S situated in one of the dimer back-bonds).…”

A first principles study of H2S adsorption and decomposition on a Ge(100) surface

“…The adsorption of sulfur on Ge(100) surface has been studied both experimentally and theoretically. [16][17][18] Previously, the S-passivation on Ge(100) surface has been investigated using low-energy electron diffraction (LEED), 8,19 high-resolution electron-energy loss spectroscopy (EELS), 20 ultraviolet photoelectron spectra (UPS), 21 X-ray photoelectron spectra (XPS), 22 temperature programmed desorption (TPD), 23 Near edge X-ray absorption ne structure (NEXAFS) 24 and multiple internal reection-Fourier transform infrared spectrometer (MIR-IR). 25 Kuhr and Ranke 21 showed in their UPS study that, H 2 S adsorbs dissociatively at 300 K on a Ge surface; then decomposes completely to form sulfur at 550 K. To understand the suldation of the Ge(100) surfaces and its possible passivating reactions, we choose H 2 S as a passivant to be adsorbed on the Ge(100) surface.…”