The effect of the degree of hydration of aluminium oxide thin films on the afterglow luminescence phenomena

Abstract

The occurrence of afterglow luminescence in aluminum oxide thin films obtained by non-electrolytic aluminum oxide conversion coating has been proved. The kinetic parameters of luminescence decay and its spectral distribution were determined using the single photon counting method. The obtained samples of hydrated aluminum oxide, supported on metallic aluminum, were subjected to dehydration and dehydroxylation. The process of dehydroxylation led to a significant (by over two orders of magnitude) increase in the efficiency of afterglow luminescence. On the basis of the luminescence decay spectrum, the emitters in the systems studied were identified to be oxygen vacancies in the structure of Al2O3, including F, F2, F+. Moreover, a high probability of involvement of electrons from the conductivity band and F and F+ states photoconversion in determination of the character of afterglow luminescence was indicated. Durations of afterglow luminescence measured for the barrier layers and porous aluminum oxide films, obtained by electrochemical oxidation, were compared. Significant differences were detected between the kinetic parameters of luminescence decay and the character of emission spectra, whose analysis permitted proposing mechanisms of the processes.