利用激光感生热电电压效应测量薄膜的各向异性泽贝克系数

Method of Measuring Anisotropy Seeback Coefficient of Thin Film Based on Laser Induced Thermoelectric Voltage Effect

利用激光对半无限大物限加热的一维热传导模型,分析La0.67 Ca0.33 MnO3 (LCMO)薄膜在KrF准分子激光照射下的温度变化。在纳秒级激光单次脉冲照射下,薄膜表面温度与照射时间的平方根成正比。并通过拟合La0.67 Ca0.33 MnO3薄膜在此激光照射下的感生电压响应信号,得到薄膜的时间常数为1.39μs。利用薄薄厚度与时间常数的关系,计算出薄膜的热扩散系数及热穿透深度,分别为4.5×108m2/s和71nm。根据测量到的脉冲响应信号的时间常数,将激光感生电压公式中薄膜厚度与热扩散系数参量简化,得到一种求符向异性泽贝克(seeback)系数的方法,计算出出La0.67 Ca0.33 MnO3的各向异性泽贝克系数为2.80μV/K。

An analytical formula of temperature distrbution in La0.87 Ca0.33MnO3 （LCMO） film irradiated by KrF excimer laser is presented using one-dimensional thermodiffusion model. The relation between surface temperature and irradiation duration of pulsed laser is obtained. Fitting the laser induced thermoelectric voltage （LITV） response waveform of LCMO film, it shows that the time constant is 1.39 μs. The thermal diffusion coefficient and conduction length of the film are calculated, and the results are 4.5 × 10^-8m^-2/s and 71 nm respectively. Based on the time constant and a simplified LITV formula, the anisotropy Seeback coefficient of thin films can be deduced, and it is 2.80 μV/K for LCMO.