Abstract

The surface structures, unoccupied and occupied electronic states, and chemical states of surface atoms for clean and (NH4)2Sx-treated InAs(111)A and (111)B surfaces have been studied using low-energy electron diffraction (LEED), inverse photoemission spectroscopy (IPES), and (x-ray and ultraviolet) photoemission spectroscopy (PES). Thermal stability of the treated surfaces upon annealing in an ultrahigh vacuum is also investigated. A diffuse (1×1) LEED pattern appears for the treated -(111)A and -(111)B surfaces annealed at 230 and 330 °C, respectively, Upon annealing the (111)B sample at 380 °C, the (1×1) structure remains and the LEED spots become clearer. For the (111)A annealed at 380 °C, the pattern changes to a clear (2×2) structure which is found for the first time for sulfurized (111) surfaces of III–V compounds. Sulfur is completely desorbed from both the (111)A and (111)B surfaces at 440 °C, exhibiting the (2×2) and (1×1) structures, respectively. IPES and PES results indicate that unoccupied and occupied dangling bonds disappear for the sulfur-adsorbed (111)A-(2×2) and (111)B-(1×1) surfaces, respectively. S 2p spectra show that sulfur is bonded to both indium and arsenic on the (111)B surface annealed at less than 340 °C and bonded only to indium at 420 °C. On the other hand, it is bonded solely to indium on the (111)A surface with and without annealing. Surface core-level shifts of In 4d and adsorption sites of sulfur are discussed.

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