Optical size effect in In$_2$O$_3$ nanostructured films

The optical size effect in In$_2$O$_3$ surface-nanostructured films is detected thanks to the study of the photoelectric properties of In$_2$O$_3$–$p$-InSe heterostructures with an anisotropic substrate. When fabricating such structures, the intrinsic oxide surface is structured in a nanoneedle ensemble whose topology depends on the structure-formation time. The features of oxide surface asperities are studied using an atomic-force microscope. The direct dependence between the surface topology and the structure of the photoresponse spectra of the heterostructures is established. The higher the density, height, and ordering of nanoneedles on the oxide surface, the more distinct the long-wavelength shift and the more pronounced the edge peak in the photoresponse spectra. All changes in the spectra are interpreted based on a model of the interaction of light with the nanoscale cellular oxide surface, which results in strong light diffraction.