薄膜生长的计算机模拟

建立了一个比较合理的三维模型,并通过模拟成像和定量计算研究了薄膜生长过程中的两个重要问题,早期成核与表面粗糙度.结果表明,薄膜的长生过程是原子吸附、迁移、脱附、连带等微观过程的积累.随着衬底温度的升高或入射率的降低,沉积在衬底上的原子逐步由各自独立的离散型分布向聚集状态转变形成岛核,并由二维岛核向三维岛核转变.衬底温度越高、入射率越低,成核尺寸越大.存在一个最佳成核温度,成核率出现一个极大值.随着衬底温度的升高,薄膜的粗糙度先降低后来又增加.存在一个生长转变温度Tr,薄膜的粗糙度达到极小值.当衬底温度小于Tr时,入射率越大,薄膜的粗糙度越大.当衬底温度大于Tr时,入射率越大,粗糙度越小.薄膜生长的主要微观机理是原子热运动对薄膜生长的影响.

Computer simulation of thin film growth

A three-dimensional kinetic Monte Carlo technique has been developed for simulating growth of thin Cu films. The model involves incident atom attachments, diffusion of the atoms and detachment of the atoms from the growing surface. A great improvement was made on calculation of the activation energy for atom diffusion based on a reasonable assumption of interaction potential (between atoms. The formation nucleation rate at the early stage and the surface roughness of the films were simulated as functions of growth substrate temperature and deposition rate. The results showed that 1) there exists an optimum growth temperature Tn, at which the nucleation rate reaches maximum. When the temperature is lower than Tn, the nucleation rates are close to the same. The nucleation rates decrease with decreasing the deposition rates as the substrate temperature is higher than Tn; 2) there exists another optimum growth temperature Tr, at which the surface roughness minimizes.