用泵浦探针法实验研究了红外激光辐照二氧化钒薄膜的相变特性.首先利用氧源-分子束外延法制备了薄膜厚度分别为20 nm、40 nm、60 nm的三组VO2单晶外延薄膜, 并且以10.6 μm的CO2连续激光作为泵浦光, 分别以1 064 nm和3 459 nm的纳秒脉冲激光作为探针光, 对这三组薄膜分别进行了辐照实验.实验发现三组薄膜相变后对1 064 nm探针光的透过率降低量平均值分别为5.26%、6.2%、8.92%, 反射率降低量分别为3.09%、6.56%、4.93%; 对3 459 nm探针光透过率降低量平均值分别为28.4%、47.78%、55.13%, 反射率升高量平均值分别为6.65%、17.87%、7.49%.结果表明: 利用分子束外延法制备的纳米级VO2薄膜相变前后对入射激光为镜面反射; 薄膜对3 459 nm探针光的相变特性比对1 064 nm探针光相变特性显著; 薄膜厚度的增加会降低相变前透过率, 但是对相变后透过率降低更为明显; 薄膜对10.6 μm CO2连续激光相变前后始终保持几乎不透.研究结果可为薄膜的应用提供参考.

To investigate the phase transformation characteristics of vanadium dioxide thin film irradiated by infrared laser, the experiment was carried out based on pump probe method. First, three groups of VO2 monocrystalline epitaxial thin films with thickness of 20 nm, 40 nm and 60 nm were prepared by oxy-molecular beam epitaxy, moreover, the CO2 continuous laser with 10.6 μm was used as the pump beam, nanosecond pulse laser with 1 064 nm and 3 459 nm wavelength were used as probe light respectively, and the three groups of films were irradiated respectively. It was found that the mean values of transmittance reduction of 1 064 nm probe laser after phase transformation of the three groups of films were 5.26%, 6.2% and 8.92%, respectively, and the reflectivity reduction was 3.09%, 6.56% and 4.93%, respectively; for the 3 459 nm probe laser, the mean values of transmittance reduction were 28.4%, 47.78%, 55.13%, and reflectance increase were 6.65%, 17.87% and 7.49% respectively. The results show that the incident laser before and after the phase transformation of VO2 thin films prepared by molecular beam epitaxy were both mirror reflected; the phase transition properties of 1 064 nm probe were not as significant as that of 3 459 nm probe; the increase of film thickness will reduce the transmittance before the phase change, while the decrease after the phase change is more obvious; before and after the phase transition, the film keeps almost opaque to CO2 laser. The investigation will provide a reference for the application of film.