Oxidation of the InSb surface at room temperature

Abstract

The formation and composition of room-temperature surface oxides on (110) orientated InSb samples was studied with ESCA and AES. The oxides are composed of a mixture of In2O3 and Sb2O5. It is shown that the Sb oxide is Sb2O5 and not Sb2O3, as has been previously generally assumed. Four surface-preparation techniques were compared: free etching, mechanical polishing, chemo-mechanical polishing and anodic oxidation. Chemo-mechanical polishing and free etching yield comparable oxide thicknesses of about 30 AA. Mechanical polishing produces a 100 AA thick disturbed oxide layer. Anodic oxidation allows a choice of the thickness but introduces a strong carbon contamination. The first monocell layer of natural oxide grows very fast, within 80 s a 15 AA layer has formed. Thereafter the oxidation is diffusion controlled and much slower. From renormalisation curves it is concluded that the oxide mainly consists of In2O3 with some Sb2O5. The In oxide stays near the oxide/bulk interface and finally after some 25 days stops further oxidation, while the Sb oxide moves towards the oxide/air interface. In contrast to thermal oxides no Sb layer is found at the oxide/bulk interface.