晶格失配对异质外延超薄膜生长中成核特性的影响

The effect of lattice mismatch on the nucleation process of heteroepitaxial growth of ultrathin film

利用动力学蒙特卡罗方法模拟了异质外延超薄膜生长中的成核过程 .研究了薄膜与衬底的晶格失配对超薄膜生长中成核密度、平均核尺寸、标度关系及生长模式的影响 .结果发现产生压 (张 )应变的晶格负 (正 )失配使生长过程更早 (迟 )从成核区进入过渡区 ,失配越大 ,这一效应越明显 .在相同的沉积条件下 ,负失配导致超薄膜形成较低的成核密度与较大的平均核尺寸 ,而正失配则相反 .成核密度满足标度关系Ns≈ (F D)χ ,随着失配度从 - 0 0 4增加到 0 0 2 ,标度系数 χ从 0 37逐渐减小到 0 33,对应超薄膜生长过程从包含二聚体扩散模式转变到无二聚体扩散模式 .此外 ,模拟结果还表明 。

The effect of lattice mismatch between the substrate and the heteroepitaxial film on the initial process of ultra thin film growth, such as the nuclear density, the average size of cluster, the scale behavior and the growth mode, is studied by the kinetic Monte Carlo method. It is found that the negative (positive) mismatch, corresponding to the compressive (tensile) strain, can induce the growth process transferring from the nucleation stage to the intermediate one earlier (later). The larger the mismatch, the more apparent the above behavior. Under the same deposition condition, the negative mismatch can bring about lower nuclear density and larger average cluster size than the positive mismatch does. Furthermore, the nuclear density is found to follow the power law of N s≈(F/D) χ , and χ decreases from 0 37 to 0 33 while the mismatch changes from -0 04 to 0 02. This behavior indicates that the growth mode of the ultra thin film changes from including dimer diffusion into excluding dimer diffusion. Additionally, the scale theory of the cluster size is found to be valid even for the heteroepitaxial growth.