Surface Electronic States of Low Temperature H-plasma Cleaned Si(100) and Ge(100) Surfaces

Abstract

The surfaces of Si(100) and Ge(100), cleaned at low temperatures by H-plasma, were studied by Angle Resolved UV-Photoemission Spectroscopy(ARUPS). In the case of Si(100), H-plasma exposure produced ordered H-terminated crystallographic structures with either a 2×1 or 1×1 LEED pattern while for Ge(100) a weak H-terminated 2x1 pattern was obtained. The hydride phases, found on the surfaces of the cleaned Si(100), were shown to depend on the temperature of the surface during H-plasma cleaning. The electronic states for the monohydride and dihydride phases were identified by ARUPS. When the plasma cleaned surface was annealed, the phase transition from the dihydride to monohydride was observed. For the Ge(100) surface, an ordered 2x1 monohydride phase was obtained from the surface cleaned at 180°C. After plasma exposure at ≤170°C a 1×1 surface was observed, but the ARUPS indicated that the surface was predominantly composed of disordered monohydride structures. After annealing above the H-dissociation temperatures, the dangling bond surface states were identified for both Si and Ge. The Si(100) and Ge(100) ARUPS spectra shifted after annealing, indicating that the H-terminated surfaces were unpinned.

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