Rosini M, Kratzer P, Magri R
Dipartimento di Fisica, Università degli Studi di Modena e Reggio Emilia and S3 Research Center of CNR-INFM, via Campi 213/A, 41100 Modena, Italy.
J Phys Condens Matter. 2009 Sep 2;21(35):355007. doi: 10.1088/0953-8984/21/35/355007. Epub 2009 Aug 7.
By using density functional theory (DFT) calculations of the potential energy surface in conjunction with the analytical solution of the master equation for the time evolution of the adatom site distribution, we study the diffusion properties of an isolated In adatom on In(x)Ga(1-x)As wetting layers (WL) deposited on the GaAs(001). The WL reconstructions considered in this study are, listed in the order of increasing In coverage: c(4 × 4), (1 × 3), (2 × 3), α(2)(2 × 4) and β(2)(2 × 4). We analyze the dependence of the diffusion properties on WL reconstruction, composition and strain, and find that: (i) diffusion on the (2 × N) reconstructions is strongly anisotropic, owing to the presence of the low barrier potential in-dimer trench, favoring the diffusion along the [Formula: see text] direction over that along the [110] direction; (ii) In diffusion at a WL coverage θ = 2/3 monolayers (ML; with composition x = 2/3) is faster than on clean GaAs(001) c(4 × 4), and decreases at θ = 1.75 ML (x = 1; e.g. InAs/GaAs(001)); (iii) diffusion and nucleation on the (2 × 4) WL is affected by the presence of adsorption sites for indium inside the As dimers; (iv) the approximation used for the exchange-correlation potential within DFT has an important effect on the description of the diffusion properties.
通过使用势能面的密度泛函理论（DFT）计算，并结合吸附原子位置分布随时间演化的主方程的解析解，我们研究了孤立的铟（In）吸附原子在沉积于砷化镓（GaAs）(001)上的In(x)Ga(1 - x)As润湿层（WL）上的扩散特性。本研究中考虑的WL重构按铟覆盖度增加的顺序列出：c(4×4)、(1×3)、(2×3)、α(2)(2×4)和β(2)(2×4)。我们分析了扩散特性对WL重构、成分和应变的依赖性，发现：(i) 在(2×N)重构上的扩散具有很强的各向异性，这是由于存在低势垒的二聚体内沟槽，有利于沿[公式：见原文]方向的扩散，而不是沿[110]方向；(ii) 在WL覆盖度θ = 2/3单层（ML；成分x = 2/3）时铟的扩散比在清洁的GaAs(001) c(4×4)上更快，而在θ = 1.75 ML（x = 1；例如InAs/GaAs(001)）时扩散速率降低；(iii) 在(2×4) WL上的扩散和成核受砷二聚体内铟吸附位点的存在影响；(iv) DFT中用于交换关联势的近似对扩散特性的描述有重要影响。
