Laser-induced Thermoelectric Voltage Effect In Strong Correlated Oxide Thin Films And Its Detector Application

The laser-induced thermoelectric voltage (LITV) effect had been found in LCMO and YBCO thin films that were grown on vicinal-cut single crystalline substrates. Recently this effect was also found in La_1-xSr_xMnO₃ (LSMO), La_1-xPb_xMnO₃ (LPMO), La_1-xSr_xCoO₃ (LSCO), Sm_1-xSr_xMnO₃ (SSMO), and La_1-xBa_xMnO₃ (LBMO) thin films. By making use of a micro-cell network model and a planar heat source model, as well as the atomic layer thermopile model, we obtained a time-dependence formula of the LITV signal, which, therefore, provides a theoretic basis for designing fast response detectors. Using the formula, the thin film parameters, such as Seebeck coefficient, thermal diffusion constant, and laser penetrating depth, can be estimated indirectly. In fact, the formula itself provides a new way to measuring some physical parameters of thin films with pulsed laser.The methods to promote the performance of the strongly correlated oxide thin film detectors were studied using the formula aforementioned. In time region: the influences of thin film parameters on sensitivity, on response time, and on figure of merit (peak voltage of LITV signal over rising time constant) were analyzed; furthermore, it was also found that the smaller the load resistance, the faster the response. In frequency region: the influence of thin film parameters on Fourier amplitude spectrum and phase spectrum were discussed as well.Based on the linear relation between the peak voltage of LITV signal and pulse laser energy deduced from the formula, peak-voltage-keep type laser energy/power meters working in broad spectrum (from ultraviolet to infrared) with fast response (from nanoseconds to picoseconds) had been developed using LCMO, YBCO, LSMO, LPMO and LSCO thin films.Time-integral type laser energy meter was put forward by making integral of the...