Ogura Shohei, Fukutani Katsuyuki
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
J Phys Condens Matter. 2009 Nov 25;21(47):474210. doi: 10.1088/0953-8984/21/47/474210. Epub 2009 Nov 5.
In heteroepitaxy, thin-film growth proceeds in two-dimensional layer-by-layer, three-dimensional island, or layer-plus-island modes depending on the growth conditions. Interlayer mass transport plays a crucial role in determining the growth mode. We investigate interlayer diffusion of Au atoms from Au islands grown on Ir(111) by scanning tunneling microscopy (STM) and kinetic Monte Carlo (KMC) simulations. STM measurements reveal that the first Au layer on Ir(111) grows in a complete layer at 100 K, whereas the Au layer grows in a three-dimensional fashion from the second Au layer at this temperature. Annealing these surfaces to 300 K reduces the higher-layer islands, indicating that Au atoms undergo step-down diffusion. By measuring the density of the top-layer islands and comparing them with the KMC simulation results, the additional step-down diffusion barrier for Au atoms to descend from the Au islands is estimated to be 0.02 eV on the first Au layer and 0.04 eV on the second Au layer. The layer dependence of the additional step-down diffusion barrier is explained in terms of the lattice mismatch between Au and underlying layers.
在异质外延中，薄膜生长根据生长条件以二维逐层、三维岛状或层加岛状模式进行。层间质量传输在确定生长模式中起着关键作用。我们通过扫描隧道显微镜（STM）和动力学蒙特卡罗（KMC）模拟研究了在Ir(111)上生长的金岛中Au原子的层间扩散。STM测量表明，Ir(111)上的第一层Au在100 K时以完整层的形式生长，而在此温度下，从第二层Au层开始，Au层以三维方式生长。将这些表面退火至300 K会减少较高层的岛状物，这表明Au原子经历了向下扩散。通过测量顶层岛状物的密度并将其与KMC模拟结果进行比较，估计Au原子从金岛下降时在第一层Au层上的额外向下扩散势垒为0.02 eV，在第二层Au层上为0.04 eV。额外向下扩散势垒的层依赖性是根据Au与下层之间的晶格失配来解释的。
