Laboratório Nacional de Nanotecnologia (LNNano), Rua Giuseppe Máximo Scolfaro 10000, 13083-100 Campinas, SP, Brazil.
ACS Nano. 2012 Nov 27;6(11):10287-95. doi: 10.1021/nn304151j. Epub 2012 Oct 17.
Freestanding, edge-supported silicon nanomembranes are defined by selective underetching of patterned silicon-on-insulator substrates. The membranes are afterward introduced into a molecular beam epitaxy chamber and overgrown with InAs, resulting in the formation of InAs islands on flat areas and at the top of the Si nanomembranes. A detailed analysis of sample morphology, island structure, and strain is carried out. Scanning electron microscopy shows that the membrane stays intact during overgrowth. Atomic force microscopy reveals a lower island density on top of the freestanding membranes, denoting a modified wetting or diffusivity in these areas. An observed bending of the membrane indicates a strain transfer from the InAs islands to the compliant substrate. X-ray diffraction and finite-element modeling indicate a nonuniform strain state of the island ensemble grown on the freestanding membrane. A simulation of the bending of the nanomembranes indicates that the islands at the center of the freestanding area are highly strained, whereas islands on the border tend to be fully relaxed. Finally, continuum elasticity calculations suggest that for a sufficiently thin membrane InAs could transfer enough strain to the membrane to allow coherent epitaxial growth, something not possible on bulk substrates.
独立式、边缘支撑的硅纳米膜是通过对图案化的绝缘体上硅衬底进行选择性刻蚀来定义的。然后，将这些薄膜引入分子束外延腔中，并在其上外延生长砷化铟，从而在平坦区域和硅纳米膜的顶部形成砷化铟岛。对样品形貌、岛结构和应变进行了详细分析。扫描电子显微镜显示，在外延生长过程中膜保持完整。原子力显微镜显示，在独立式膜的顶部岛的密度较低，表明这些区域的润湿性或扩散性发生了改变。观察到的膜弯曲表明应变从砷化铟岛传递到弹性衬底。X 射线衍射和有限元建模表明，在独立式膜上生长的岛的集合体具有不均匀的应变状态。对纳米膜弯曲的模拟表明，独立区域中心的岛处于高度应变状态，而边缘的岛则趋于完全松弛。最后，连续弹性体计算表明，对于足够薄的膜，砷化铟可以将足够的应变传递到膜上，以允许相干外延生长，这在体衬底上是不可能的。
