Cesium-induced electronic states and space-charge-layer formation in Cs/InSb(110) interface

We report a study of the electronic properties of Cs overlayers on the narrow-band-gap III-V semiconductor InSb(110) as determined by means of photoemission and high-resolution electron-energy-loss spectroscopy. The electric and electronic properties of Cs-deposited on InSb(110) present two distinguishable phases, which can be related to the morphological transition observed in the scanning tunneling microscopy from one-dimensional chains to the two-dimensional (2D) Cs layer. The earlier stages of Cs adsorption induce an accumulation layer, while an additional Cs deposition results in a depletion of carriers in coincidence with the appearance of Cs-induced states in the semiconductor gap. When a 2D layer of cesium is formed on the InSb(110) surface, the interface is insulating with the surface band gap at 0.65 eV, larger than the underlying InSb bulk gap (0.175 eV at room temperature).