Strong ultraviolet and violet photoluminescence from Si-based anodic porous alumina films

We have investigated photoluminescence (PL) from Si-based anodic porous alumina films formed by realtime controlled anodization of electron-beam evaporated Al films. As-anodized samples show three strong PL bands at 295, 340, and 395 nm. These bands blueshift and their intensities decrease after the samples are annealed. When the annealing temperature increases to 1000 degreesC, the blueshift becomes specially pronounced and meanwhile the structures of the films develop toward crystalline Al2O3 Based on discussions on the thermal annealing behaviors of the PL and PL excitation spectra, we suggest that optical transitions in oxygen-related defects, F+ (oxygen vacancy with one electron) centers, are responsible for the observed ultraviolet and violet PL.