A new photoconductive medium made from lanthanum titanate (LTO) on a substrate of strontium titanate (STO) holds promise1 as material for designing new electronic devices.
The researchers grew nano-sized layers of LTO on STO single crystal surface using pulsed-laser deposition technique. To apply electric field, they fabricated field-effect devices by depositing a chromium–silver bilayer on the other side of the STO substrate. This structure was exposed to ultraviolet light and electric field in the temperature range of 10 to 300K. The resistance of the LTO film dropped instantaneously on exposure to light.
The overall change in resistance due to the electric field and light is nearly the same as in the light-only experiment. On exposure to light, LTO loses electrons which move towards STO and accumulate at the interface of LTO and STO as two dimensional electron gases.
"The two-dimensional electron gas seen at the interface of LTO and STO can be tailored to fabricate high speed transistors and quantum dots," says lead researcher Ramesh Chandra Budhani. The sensitivity to light further makes such systems useful for sensor and detector applications, he adds.
