Blue photoluminescence of sponge-like highly porous alumina synthesized in hydrofluoric acid based electrolytes

Abstract

For the first time nanostructures of anodized aluminum oxide (AAO) were synthesized using hydrofluoric acid based electrolytes under potentiostatic mode with varied oxidation conditions. As-grown oxide layers were amorphous and had sponge-like disordered structure with ramified pores system of 50 to 300 nm diameters. All samples under daylight demonstrated blue emission with power up to 10 μW that was seen by naked eye. It was shown that integral intensity of photoluminescence (PL) emission band in 350 - 650 range increases up to 7 - 60 times depending on synthesis details. Observed PL spectra were approximated by superposition of two components with Emax = 2.74 and 2.44 eV, FWHM = 0.63 and 0.53 eV. It was substantiated that studied emission have intrinsic origin and can be attributed to F22+ - and F2-centers.