Thermal and Optoelectrical Analysis of La_0.7Sr_0.3MnO₃ Thin Film Thermistor in 8–12 μm Range for Uncooled Microbolometer Application

Abstract

La0.7Sr0.3MnO3 as a sensing material has shown an amazing potential for uncooled thermal imaging application. Here we report the fabrication of a La0.7Sr0.3MnO3 (LSMO) thin film thermistor on a Si wafer and explored two prime figure-of-merit such as temperature coefficient of resistance (TCR) and optical responsivity, which are very useful parameters to compare the performance with any thermal sensor. The LSMO films were deposited on a SrTiO3 (STO) buffer layer with Si/SiO2 as a substrate, by a pulsed laser deposition (PLD) technique. The crystallinity and surface topography of the films were analyzed by X-ray diffraction (XRD) and atomic force microscopy (AFM). The fabricated device was then analyzed for its thermal and electrical characteristics to validate its suitability as an IR sensor. The fabricated device shows very sharp metal-to-insulator (TMI) phase transition temperature at 150 K and very high TCR of +4% K -1 and -4%K -1 near 100 K and 200 K respectively, when the temperature was sweeped from 10 K to 300 K. Fabricated Thermistor shows very good thermal response and recovery when subjected to an alternating on-off cycle of IR lamp (150 W) illumination, which confirms its suitability for the highspeed thermal imaging application. The experimental analysis shows highest responsivity of ~21085 V/W at 8.5 µm, which falls in the Long-Wave Infrared (LWIR) region, which is an ideal IR band for any thermal imaging application.