La_(2/3)Ca_(1/3)MnO_3薄膜的光致电阻率变化特性

The change of photo-induced resistivity properties in La_(2/3)Ca_(1/3)MnO_3 thin films

射频磁控溅射法制备了La2 3Ca1 3MnO3纳米薄膜 (LCMO) .该薄膜发生FM PM相变的转变点温度为Tc≈ 30 8K(近似为电阻峰值温度Tp) ;在不同温度下的光电导性质实验表明所制备的LCMO薄膜在连续激光作用时低温段(T <Tc)表现为光致电阻率增大效应 ,即ΔR R >0 ,并在R T曲线拐点附近取得极大值 ,(ΔR R) max=4 3 5 % ;当T>Tc 时 ,ΔR R <0 ,即光电导效应 .调制激光脉冲光响应实验发现 ,光致信号强度和温度及偏置电流之间存在非线性关系 :光致电阻率增大信号极大值为偏置电流的二次函数 ,而极大值对应的温度和偏置电流成线性关系 ,同时 ,光响应有一个截止温度 ,并且存在最佳光响应偏置电流和温度条件 .

Photo-induced resistivity change p has been studied in perovskite manganite La 2/3Ca 1/3MnO 3 thin films with a continous wave laser and modulated laser pulses in this paper. Experimental results show that in the sample films, the maximum of photo-induced resistivity change(ΔR/R) max can reach 43.5%,which is a very exciting figure in this research field. Modulated laser pulse induced signal intensity has a highly nonlinear relation with the applied current and temperature. The maximum of photo-induced resistivity increase is a second power function of the applied current, while the temperature at which the maximum appears is proportional to the bias current. There exist an optimal bias current and a temperature for optical response in this film. These results are attributed to the optical excited e g↓ carriers and polarons.