Time-resolved luminescence of defects and Cr 3+ impurity centers in nanosized alumina crystals under vacuum-ultraviolet excitation

Abstract

The photoluminescence (PL) of intrinsic defects and Cr 3+ impurity centers in nanosized alumina (Al 2O 3) crystals of various phase compositions (δ + θ and α phases) has been studied by the method of time-resolved spectroscopy with vacuum-ultraviolet (VUV) excitation at T = 7. 5 and 295 K. It is established that the PL excitation spectrum and its kinetic parameters for α-Al 2O 3 phase can change depending on the crystal grain size. In α-Al 2O 3 samples with grain sizes below 100 nm, excitons localized on Cr 3+ impurity centers and surface-modified defects of the crystal structure are observed even at T = 295 K. Manifestations of these exciton states in the PL spectra strongly depend on the grain size. © 2012 Pleiades Publishing, Ltd.