铝传感层蒸镀速率对飞秒激光抽运探测热反射方法测量热导率影响的研究

Effect of deposition rate of aluminum transducer on thermal conductivity measurement by femto-second laser pump-probe technique

对飞秒激光抽运探测热反射实验中的一个关键因素传感层进行了研究，发现铝传感层的蒸镀速率对飞秒激光抽运实验有着很大的影响。分别在3种不同类型的硅片和玻璃片基底上用不同的蒸镀速率蒸镀了100nnm的铝膜蒸镀速率控制在2×10^-10到15×10^-10m／s。通过扫描电子显微镜（SEM）和X射线反射（XRR）研究了蒸镀铝膜表面的形貌及铝膜的厚度。基于飞秒激光抽运探测热反射方法对基底的热导率进行了测量，发现随着蒸镀速率的增大，不同基底测量得到的热导率呈现一致的规律。结果表明，蒸镀速率越大，铝传感层的晶粒越大，传感层的体积热容越小，当蒸镀速率大到一定程度时，由于晶粒的不规则度越来越大，反过来又影响体积热容的大小，从而影响了飞秒激光抽运探测热反射。

Aluminum （A1） films with thickness of 100 nm were grown on 3 different silicon and glass substrates by electron beam evaporation. The deposition rates were adjusted in the range between 2 and 15A/s. The structure, surface morphology and thickness of the as-deposited A1 films were studied using scanning electron microscopy （SEM） and X-ray reflectivity（XRR）. Femto-second laser pump-probe technique was used to measure the thermal properties of substrates deposited A1 films. SEM imaging of the films showed that the mean grain size of thin A1 films on all of the substrates increased with increase of the deposition. The thermal conductivity of the substrates has the same trend as the deposition rate increased. The observed effects of the deposition rate on the femto-second laser pump-probe experiment are explained by the change of volumetric capacity of aluminum transducer.