Microscopic structure of the discommensurate phases in Ge(111)/Ga. II. Domain superstructure and discommensurations.
Microscopic structure of the discommensurate phases in Ge(111)/Ga. II. Domain superstructure and discommensurations.
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DOI：
10.1103/physrevb.51.9965
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发表时间：
1995-04
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影响因子：
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通讯作者：
Boehringer;Molinàs-Mata;Artacho;Zegenhagen
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文献类型：
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作者：
Boehringer;Molinàs-Mata;Artacho;Zegenhagen
本文报道了Ge（111）/Ga系统中两种不同公度相γ和β的原子分辨扫描隧道显微镜（STM）图像。在这两个阶段中，Ga原子取代衬底表面层的Ge原子，导致畴内的局部（1× 1）结构。在β相中，其发生在比γ相稍高的Ga覆盖率下，在一半的畴中可见堆垛层错。磁畴由基本的位错隔开，即所谓的畴壁。在本研究中，我们专注于这些墙壁的微观结构，这是很难访问的STM以外的方法的问题。从STM数据中，我们推导出β相壁的微观模型，其中几乎所有的悬挂键都是饱和的-与γ相中的情况相反。这种能量上有利的情况是由于堆垛层错的存在而实现的。我们提出，由于β相壁中所有悬挂键的去除而导致的能量增益超过了与堆垛层错相关的能量损失，从而驱动了从γ相到β相的转变。
We present atomically resolved scanning tunneling microscope (STM) images of two of the discommensurate phases—γ and β—occurring in the system Ge (111)/Ga. In both phases Ga atoms substitute the Ge atoms of the substrate surface layer, resulting in a local (1× 1) structure within domains. In the β phase, which occurs at slightly higher Ga coverages than the γ phase, a stacking fault is visible in half of the domains. The domains are separated by elementary discommensurations, so-called domain walls. In the present study we focus on the microscopic structure of these walls—a problem that is hard to access with methods other than STM. From the STM data we deduce a microscopic model of the walls of the β phase, where virtually all dangling bonds are saturated—in contrast to the situation in the γ phase. This energetically favorable situation is enabled by the presence of the stacking fault. We propose that the gain in energy due to the removal of all dangling bonds in the walls of the β phase exceeds the loss in energy associated with the stacking fault, driving the transition from the γ to the β phase.