超高真空脉冲激光沉积Au、U单层膜及Au/U/Au复合膜研究

摘要

采用超高真空脉冲激光沉积(PLD)方法,在单晶Si基底表面制备了单层Au、单层U薄膜和Au/U/Au复合薄膜,应用SEM、白光干涉轮廓分析和AES分析,研究了靶基距、基片温度和激光能量对薄膜形貌、成分的影响.目前的实验结果显示,PLD所制备的Au、U薄膜表面有μm级以下粒径的液滴产生,在液滴较少位置,薄膜表面粗糙度Ra小于1 nm,在包含大液滴位置,Ra不超过15 nm.在相同沉积条件下,U薄膜表面液滴数量大于Au薄膜.优化单层薄膜沉积工艺后制备的Au/U/Au复合膜厚度约为195 nm,均方根粗糙度Rq在0.3～1.5 nm之间.AES分析显示,Au/U/Au复合膜中强化学活性的铀呈金属状态,复合膜中的氧含量低于5％(原子百分数),表层Au薄膜对U薄膜起到了良好的防氧化作用.在沉积工艺中,通过减小激光功率、增大靶基距并适当升高基片温度,可减少液滴的数量及粒径.%Metallic uranium has the characteristic of high efficiency of laser to X-ray energy conversion. The ultra-high vacuum pulsed-laser deposition (PLD) system was used to prepare Au film, U film and Au/U/Au multilayer film on single Si (100) substrate to prevent the oxidation of uranium. The SEM pictures show that there are spherical metal droplets with diameters less than several microns on the Au and U film surface prepared by PLD under present technology. The surface roughness Ra of less droplet region is less than 1 nm, and the big droplet containing region is less than 15 nm. The amount of droplet on U film surface is much more than Au film surface under the same deposition condition. The Au/U/Au multilayer film with thickness about 195 nm and Rq between 0. 3-1. 5 nm was prepared after PLD technology optimization. AES depth profile results reveal that the oxygen content in Au/U/Au multilayer film is less than 5% (atomic percentage), and uranium remains in metal chemical state. It may be effective to reduce the number and size of droplets by reducing the laser power, increasing the distance of target from the substrate and appropriately rising the substrate temperature.