Institute of Semiconductor Physics SB RAS, Academician Lavrentiev Avenue 13, Novosibirsk 630090, Russia.
Phys Rev Lett. 2013 Jul 19;111(3):036105. doi: 10.1103/PhysRevLett.111.036105.
The critical terrace width λ for 2D island nucleation and growth (2DNG) on large-scale atomically flat terraces of a step-bunched Si(111)-(7×7) surface has been studied by in situ ultrahigh vacuum reflection electron microscopy as a function of the substrate temperature T and Si deposition rate R. The dependence of λ(2)(R) is characterized by a power law with scaling exponent χ=1.36-1.46, validating an attachment limited (AL) growth kinetics up to 720 °C. At this temperature, the Arrhenius dependencies lnλ(2)(1/T) change their slope, so that the effective 2DNG activation energy E(2D) drops from 2.4 eV down to 0.5 eV at T>720 °C. We first show that the E(2D) change is caused by a transition between AL and DL (diffusion limited) growth kinetics accompanied by a step shape transformation. The AL growth mode is characterized by kinetic length d(-)~10(5)a and the preferential step-down attachment of atoms to steps limited by an energy barrier E(ES)(-)≈0.9 eV.
二维岛状形核和生长（2DNG）在具有台阶堆积 Si(111)-(7×7)表面的大规模原子级平坦台阶上的临界平台宽度 λ 已通过原位超高真空反射电子显微镜研究了其作为衬底温度 T 和 Si 沉积速率 R 的函数。λ(2)(R)的依赖性由标度指数 χ=1.36-1.46 的幂律来表征，验证了直至 720°C 的附着限制（AL）生长动力学。在该温度下，lnλ(2)(1/T)的 Arrhenius 依赖性改变了斜率，使得有效 2DNG 激活能 E(2D)从 2.4 eV 降低到 T>720°C 时的 0.5 eV。我们首先表明，E(2D)的变化是由 AL 和 DL（扩散限制）生长动力学之间的转变引起的，伴随着台阶形状的转变。AL 生长模式的特征是动力学长度 d(-)~10(5)a，原子优先向下沿台阶附着，受能量势垒 E(ES)(-)≈0.9 eV 限制。
