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arXiv 0907.4770cond-mat.mes-hallcond-mat.mtrl-sci
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Si(001)表面低温分子束外延生长Ge Hut团簇的分类

Classification of Ge hut clusters in the arrays formed by molecular beam epitaxy at low temperatures on the Si(001) surface

Larisa V Arapkina, Vladimir A Yuryev

摘要:

本文用原位扫描隧道显微镜对低温真空分子束外延过程中Si(001)表面形成量子点阵列的Ge hut团簇进行了形态学研究和分类。两种主要的Ge hut团簇组成的阵列-金字塔和楔形的-已被发现有不同的原子结构。由此推断,金字塔和楔形体之间的形状过渡是不可能的。在阵列形成的初始阶段,金字塔形和楔形形的成核概率等于1/2。随着沉积锗量的增加,楔形物成为主要物种。随着Ge覆盖率的增加,阵列中金字塔的分数和密度迅速下降。的衍生类型的集群-方尖碑(或截断楔)和吸积楔-已被发现和调查的第一次,他们已被发现开始占主导地位,在高Ge覆盖。方尖碑起源于楔形体,这是由于楔形体的高度限制和梯形刻面的进一步生长。方尖碑的顶点由一组平行的(001)脊形成。簇阵列的均匀性已被证明是由楔形簇的长度控制。在低生长温度(360 ℃)的成核过程中观察到的新的集群的阵列生长在所有的Ge覆盖率的值,除了一个特定的点,在该点上的阵列是更均匀的比在更高或更低的覆盖率。在较高的温度下(530 ℃),在阵列形成的初始阶段之后没有观察到簇成核。

英文摘要:

Morphological investigations and classification of Ge hut clusters forming the arrays of quantum dots on the Si(001) surface at low temperatures in the process of the ultrahigh vacuum molecular beam epitaxy have been carried out using in situ scanning tunnelling microscopy. Two main species of Ge hut clusters composing the arrays - pyramidal and wedge-shaped ones - have been found to have different atomic structures. The inference is made that shape transitions between pyramids and wedges are impossible. The nucleation probabilities of pyramids and wedges equal 1/2 at the initial stage of the array formation. The wedges become the dominating species as the amount of the deposited germanium is increased. A fraction and a density of the pyramids in the arrays are rapidly decreased with the growth of Ge coverage. The derivative types of the clusters - obelisks (or truncated wedges) and accreted wedges - have been revealed and investigated for the first time, they have been found to start dominating at high Ge coverages. The obelisks originate from the wedges as a result of their height limitation and further growth of trapezoid facets. The apexes of the obelisks are formed by sets of the parallel (001) ridges. The uniformity of the cluster arrays have been evidenced to be controlled by the length of the wedge-like clusters. At low growth temperatures (360C) nucleation of new clusters is observed during the array growth at all values of Ge coverage except for a particular point at which the arrays are more uniform than at higher or lower coverages. At higher (530C) temperatures cluster nucleation has not been observed after the initial stage of the array formation.

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