Photo-induced persistent enhancement of dielectric permittivity in Zn:BaAl_2O_4

摘要

Photo-induced persistent enhancement of dielectric permittivity has been demonstrated in Ba(Al_(0.97)Zn_(0.03))_2O_(4-δ) (BAZ) with a stuffed-tridymite-type structure under photo-irradiation with an energy of 3.4 eV (365 nm). The dielectric permittivity is enhanced by more than 20% and shows a weak frequency dependency. The dielectric loss (tanδ) shows only a slight increment for frequencies up to 1 MHz, indicating that the incremental change in dielectric permittivity of BAZ is not caused by photoconduction. This enhancement persists on termination of photo-irradiation. The results of this study suggest that the origin of the enhancement of dielectric permittivity is related to the dielectric response of the photo-excited dipole moments, which are composed of photo-excited electrons trapped in in-gap states and photo-excited holes generated in the valence band maximum. These findings shed light on the development of devices that can control dielectric properties by photo-irradiation.