IHP, Im Technologiepark 25, D-15236 Frankfurt (Oder), Germany.
Nanotechnology. 2012 Sep 7;23(35):355706. doi: 10.1088/0957-4484/23/35/355706. Epub 2012 Aug 15.
We study the growth and relaxation processes of Ge nano-clusters selectively grown by chemical vapor deposition on free-standing 90 nm wide Si(001) nano-pillars with a thin Si(0.23)Ge(0.77) buffer layer. We found that the dome-shaped SiGe layer with a height of about 28 nm as well as the Ge dot deposited on top of it partially relaxes, mainly by elastic lattice bending. The Si nano-pillar shows a clear compliance behavior-an elastic response of the substrate on the growing film-with the tensile strained top part of the pillar. Additional annealing at 800 °C leads to the generation of misfit dislocation and reduces the compliance effect significantly. This example demonstrates that despite the compressive strain generated due to the surrounding SiO(2) growth mask it is possible to realize an overall tensile strain in the Si nano-pillar and following a compliant substrate effect by using a SiGe buffer layer. We further show that the SiGe buffer is able to improve the structural quality of the Ge nano-dot.
我们研究了通过化学气相沉积在自由-standing90nm 宽的 Si(001)纳米柱上选择性生长的 Ge 纳米团簇的生长和弛豫过程，这些纳米柱具有一个薄的 Si(0.23)Ge(0.77)缓冲层。我们发现，高度约为 28nm 的穹顶形 SiGe 层以及沉积在其顶部的 Ge 点部分弛豫，主要通过弹性晶格弯曲。Si 纳米柱表现出明显的顺应行为，即基底对生长膜的弹性响应，其顶部部分受拉伸应变。在 800°C 下进一步退火会导致失配位错的产生，并显著降低顺应性效应。这个例子表明，尽管由于周围的 SiO2 生长掩模产生了压缩应变，但通过使用 SiGe 缓冲层，仍然有可能实现 Si 纳米柱的整体拉伸应变和顺应性基底效应。我们进一步表明，SiGe 缓冲层能够提高 Ge 纳米点的结构质量。
