Effects of the ion-implantation on the thermoluminescence spectra of strontium titanate

Thermoluminescence of strontium titanate at low temperature is characterised by long wavelength emission centred near 800nm which contains at least three overlapping luminescence bands. The thermoluminescence is excited by X-ray irradiation at 25 K of an entire sample. Room temperature ion-implantation into the surface layer changes the low temperature TL signals both in terms of their relative intensities and peak temperatures, as well as modifying the emission spectra. Such an intense perturbation of the bulk signals resulting from surface ion beam implantation is extremely unusual. However, it is well documented that for strontium titanate there are a variety of low temperature relaxations of the structure, and even phase transitions, which are highly sensitive to the presence of intrinsic defects, impurities and stresses. The ion-implantation damage in the surface is thus thought to act as a stress nucleation zone from which such relaxations can propagate throughout the entire crystal. There are consequent changes in the thermoluminescence in terms of defect stability and glow peak temperature. Details of such changes and modifications of emission spectra are reported. (C) 2004 Published by Elsevier B.V.