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Articles you may be interested inPhotovoltage imaging of a single As-vacancy at a GaAs(110) surface: Evidence for electron trapping by a charged defect?

The interaction of UHV cleaved FeS2(100) surfaces with adsorbed H2O as an electron donor and adsorbed Br2 as an electron acceptor has been studied with LEED, LEISS, UPS, and XPS to simulate semiconductor/electrolyte interfaces in UHV. The (100) cleavage plane is characterized by a c(2 × 2) or p(√2 × 2)R 45° LEED pattern which is interpreted in terms of the unreconstructed FeS2 surface. H2O is molecularly adsorbed at low temperatures (100 K) and desorbs completely at room temperature (RT). LEIS‐spectra taken at low coverages (<0.5 ML) suggest a preferential interaction with the Fe sites. Br2 is ionosorbed at low coverages (<0.5 ML) as well interacting specifically with Fe‐sites. It is molecularly adsorbed at higher coverages. The ionosorbed part does not desorb at RT. The behavior of specific adsorption is related to the electronic nature of the band edges which are derived from Fe d‐states.

The effect of passing cathodic currents at potentials of hydrogen evolution through differently pretreated n‐type pyrite (FeS2) electrodes is studied by XPS. It is shown that hydrogen evolution results in an etching of the crystal via dissolution of FeS2. Surfaces that are destroyed through sputtering or polishing are restored through this etching procedure. (100) and (111) surfaces behave similar to each other. When depositing gold onto the electrochemically etched surface in ultrahigh vacuum no change of the band bending of the clean surface (650 meV) is observed. An abrupt interface with FeS‐like defects in the pyrite is formed. Deposition of platinum yields a ternary PtFeS interlayer between pyrite and metallic Pt. The band bending is reduced by 200 meV during contact formation. Concerning the chemical composition and the electronic structure the etched surfaces behave nearly identical to clean (100) cleavage planes of pyrite.