Oxygen adsorption on the indium antimonide (110) surface

The formation and structure of the natural oxide on UHV-cleaved InSb(110) surfaces are studied using ultraviolet photoemission spectroscopy (UPS), electron-energy-loss spectroscopy (ELS), and spectroscopic ellipsometry ($1.5<h\nu <4.5\mathrm{}$ eV). The exposure of the as-cleaved surface to small amounts of ${\mathrm{O}}_2$ [∼30 L (1 Langmuir = ${10}^{-6\mathrm{}}$ Torr sec)] causes a slight rearrangement of surface atoms leading to changes in the shape of the upper valence band and in the surface optical dielectric function. Increasing ${\mathrm{O}}_2$ exposure causes oxide formation which is first detectable (as a chemical shift in the $\mathrm{In}4d$ UPS) at ∼ ${10}^5$ L. The oxide growth is spatially uniform, and the first monolayer is complete by approximately ${10}^6$ L. Overall, the oxide is a mixture of In and Sb oxides and is a good insulator. The outermost surface of the oxide appears to be Sb rich. ELS transitions involving intrinsic surface states are observed in the oxide and possibly also on the clean surface.