激光感生热电电压信号的衰减时间研究

Decay time of laser-induced thermoelectric voltage signals

为了研究激光感生热电电压(laser-induced thermoelectric voltage,LITV)信号的衰减时间与薄膜物性参量的定量关系,采用脉冲激光沉积法制备了 YBa_2Cu_3O_(7-x),La(0.67)Ca_(0.33)MnO_3,La_(0.67)Pb_(0.33)MnO_3薄膜,测量了248nm 的脉冲激光辐照在薄膜中诱导产生的 LITV 信号,并且基于激光与薄膜相互作用的光热过程推导出的 LITV 信号衰减时间常数的表达式。结果表明,LITV 信号呈指数衰减,变化规律与 LITV 效应的理论模型相吻合;LITV 信号的衰减时间仅决定于薄膜的热传导性能,是薄膜热扩散系数的函数;根据 LITV 信号的衰减时间可以计算薄膜的热扩散系数,从而提出通过测量LITV 信号的衰减时间来研究薄膜热扩散系数的新方法。

In order to get the quantitative relationship between the decay time constant （ DTC ） of the laser-induced thermoelectric voltage （LITV） signals and the physical parameters of the thin films, YBa2Cu3O7-x,La0.67Ca0.33MnO3,La0.67Pb0.33MnO thin films were prepared by means of pulsed laser deposition. The corresponding LITV signals were detected with these films illuminated by 248nm pulsed laser. An exact function of DTC was deduced based on the interaction between the laser pulses and the fihns. The measured LITV signals were observed decaying exponentially, which is in agreement with the model of LITV effect. The DTC is just limited by the thermal transition properties of the films, and is the function of the thermal diffusion constant. According to the measured decay time, the thermal diffusion constants of the thin films can be calculated. Thus the measurement of DTC of LITV signals is a new way to investigate the thermal diffusion constant of thin films.