Cu薄膜的瞬态反射率及退火处理的影响

Transient reflectivity of Cu films and influence of annealing

为了研究激光辐照金属薄膜后的超快热化动力学过程,利用磁控溅射技术在玻璃衬底上制备了Cu薄膜样品,同时取部分样品进行不同温度的退火处理.运用飞秒激光泵浦-探测技术观测了薄膜表面的反射率变化,研究了薄膜退火处理对反射率的影响.结果表明:飞秒激光作用下,Cu薄膜的瞬态反射率曲线分为稳定、快速上升、衰减和恢复4个阶段;退火处理对反射率曲线的峰值和衰减阶段的时间有影响,退火温度越高,反射率变化的峰值越小,衰减阶段所用的时间越长,即电子的冷却速率越慢;基于双温模型预测的电子温度与试验结果大致吻合,但是预测的电子冷却时间比试验要长.

A In order to study ultrafast thermalization dynamics of short-pulsed laser irradiated metal, Cu films were deposited on glass substrates by magnetron sputtering, and some samples were annealed at dif- ferent temperatures. The transient reflectivity of films was detected by femtosecond laser pump-probe, and the influence of annealing on transient reflectivity was also discussed. The results show that the tran- sient reflectivity curve of Cu films can be divided into four stages of stable state, rapid increase, attenua- tion and recover. The peak value and the delay time of attenuation stage of transient refleetivity curve are sensitive to annealing. With increased annealing temperature, the attenuation stage time is increased with decreased peak value, which means the cooling rate is slow. The predicted electron temperature based on two-temperature model is consistent with experimental data, but the predicted electron cooling time is lon- ger than that of experiment.