Photoresponse in tilted Bi_2Sr_2Co_2O_y, thin films with nano-structured silver layer as the light absorber

摘要

Layered cobalt oxide thin films with tilted structures exhibit large light-induced transverse voltage signals due to the transverse thermoelectric effect and have great potential applications in uncooled broad-band light detectors. In this paper, we investigated the photoresponse in c-axis tilted Bi_2Sr_2Co_2O_y thin films coated with a layer of nano-structured silver light absorber by using a 532 nm continuous wave laser as the incident light. The incidence direction of the laser beam was directly perpendicular to the sample surface. The laser spot was located at the centre position between the two electrodes and its diameter was about 2 mm. The induced lateral voltage signals were recorded using a 2400 Keithley source meter. Open-circuit voltage signals were observed when the sample surface was illuminated by the 532 nm radiation. Appropriate lateral size and thickness of the nano-structured silver layer can increase the photo-thermal-electric conversion efficiency in this photoresponse process due to the effective absorption of the light at the absorption layer, leading to the improvement in voltage sensitivity. The result offers important guidance of designing the light absorption layer for high performance broad-band light detectors based on the light-induced transverse voltage effect.