Photoinduced phenomena and shallow levels in K_1−xLi_xTaO₃

Abstract

Li admixture greatly enhances n-type photoconductivity of KTaO³ crystals. Thermally stimulated current experiments indicate that this phenomenon is related with the presence of hole-trapping levels with depths of 50–100 meV. This is in good agreement with recent energy structure calculations showing the existence of levels at these energies above the top of the VB, due to perturbed O^2- p-states. The study of visible photoluminescence and thermo-luminescence shows that the hole-trapping centre also controls the emission process. We conclude in favour of radiative recombination involving O⁻Ta⁴⁺polaron pairs.

Keywords: ferroelectric perovskites: photoconductivity

Key Words:

• photoluminescence