Passivation and reconstruction-dependent electron accumulation at sulphur treated InAs(001) surfaces

The effects of in situ sulphur passivation on the electronic properties of n-type InAs(0 0 1) have been studied using X-ray photoemission spectroscopy and high resolution electron energy loss spectroscopy coupled with space-charge layer calculations. Surfaces passivated by sulphur dosing followed by arsenic capping were annealed in vacuum to progressively remove the protective layers. For disordered surfaces with a sulphur coverage of almost 2 monolayers (ML), complex surface plasmon modes were observed due to strong electron accumulation at the surface, with downward band bending around 600 meV. For (2 x 1) reconstructed surfaces (sulphur coverage