Dresden 2003 – scientific programme

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HL: Halbleiterphysik

HL 40: Grenz- und Oberfl
ächen

HL 40.3: Talk

Thursday, March 27, 2003, 11:30–11:45, BEY/154

Role of Solvent in Adsorbtion at Semiconductor/Electrolyte Interface — •Mikhail Lebedev, Thomas Mayer, and Wolfram Jaegermann — TU-Darmstadt, Surface Science Division, Petersenstr. 23, 64287 Darmstadt

The vast majority of chemical processes at semiconductor surfaces proceed at the interface between the solid and solutions, where solvation phenomena are of great importance. The role of the solvent in adsorbate interaction with semiconductor surfaces is studied by the example of the adsorption of hydrosulfide-ions at oxide-free GaAs(100) surface from different solvents in nitrogen atmosphere. XPS shows that the As-S bonds formed in aqueous sulfide solution have lower ionicity (minimal chemical shift). The treatment with alcoholic sulfide solutions with low dielectric constant results in the formation of As-S bonds with increased ionicity, as evidenced by increased chemical shifts, as well as by increased ionization energy of the semiconductor. The Ga-S component in core-level spectra is independent on the solvent. However, the valence-band spectra contain features related to Ga-S bonds with the solvent-dependent binding energy. Charge, localized in surface states decreases with the decrease of the solvent dielectric constant. Ab initio calculations have shown that these effects are related to variations in hydrosulfide-ions reactivity due to the different influence of the solvate shell in different solutions.