Dielectric changes under light are nothing new, but in the case of LaAl0.99Zn0.01O3-δ it is not accompanied by an increase in dielectric conductivity – it remains an insulator throughout the process. “We have demonstrated the existence of the photodielectric effect experimentally,” said researcher Hiroki Taniguchi.
It works under the illumination of a blue LED at least from 100Hz to 1Mz – the limits of the dielectric measuring instrument.
Exactly what is going on is not yet know, but LaAlO3 – the same stuff without zinc doping – doesn’t do it, suggests it has to do with defects in the material.
Light excites electrons into higher (quantized) energy states, but the quantum states of defects are confined to smaller regions, said the University, which may be preventing these photo-excited electrons from travelling far enough to generate an electric current. The hypothesis being that the electrons remain trapped which leads to more electrical insulation of the dielectric material.
Further research will look to enhance the effect, minimise any energy dissipation due to a drop of dielectric properties, and optimise the material fabrication process, Taniguchi said.
What they also want to do, is find an application for photo-dielectrics.
The work is published in Applied Physics Letters.