XPS and AFM studies of surface chemistry and morphology of In₂O₃ ultrathin films deposited by rheotaxial growth and vacuum oxidation after air exposure

In this paper we present the results of an XPS study of the surface chemistry of In₂O₃ (IO) ultrathin deposited by rheotaxial growth and vacuum oxidation after their air exposure and subsequent UHV annealing. For the freshly deposited RGVO IO ultrathin films the relative [O]/[In] concentration is equal to 1.17 ±0.05. After exposure to air it increases to 1.25 ±0.05. However, a strong C contamination appears, confirmed by the relative [C]/[In] concentration that is equal to 1.07 ±0.05. After subsequent UHV annealing at 200 the relative [O]/[In] concentration remains and only slightly increases to 1.30 ±0.05 after subsequent UHV annealing at 350 C. After this process the relative [C]/[In] concentration decreases to 0.43 ±0.05. The additional AFM experiments showed that the RGVO IO ultrathin films exhibit the granular-type surface morphology, with an average grain height and width in the range of 2-5 nm, and 10-50 nm, respectively, and an average roughness of 1.1 nm.