University of Wisconsin-Madison, Madison, WI, 53706, USA.
Nanoscale Res Lett. 2012 Nov 15;7(1):628. doi: 10.1186/1556-276X-7-628.
New phenomena arise in single-crystal semiconductors when these are fabricated in very thin sheets, with thickness at the nanometer scale. We review recent research on Si and Ge nanomembranes, including the use of elastic strain sharing, layer release, and transfer, that demonstrate new science and enable the fabrication of materials with unique properties. Strain engineering produces new strained forms of Si or Ge not possible in nature, new layered structures, defect-free SiGe sheets, and new electronic band structure and photonic properties. Through-membrane elastic interactions cause the double-sided ordering of epitaxially grown nanostressors on Si nanomembranes, resulting in a spatially and periodically varying strain field in the thin crystalline semiconductor sheet. The inherent influence of strain on the band structure creates band gap modulation, thereby creating effectively a single-element electronic superlattice. Conversely, large-enough externally applied strain can make Ge a direct-band gap semiconductor, giving promise for Group IV element light sources.
当这些单晶体半导体被制造得非常薄，厚度达到纳米尺度时，就会出现新的现象。我们回顾了最近关于 Si 和 Ge 纳米膜的研究，包括利用弹性应变共享、层释放和转移，这些研究展示了新的科学，并能够制造具有独特性能的材料。应变工程产生了自然界中不可能存在的新型应变 Si 或 Ge 形式、新型层状结构、无缺陷的 SiGe 薄片以及新型电子能带结构和光子特性。通过膜的弹性相互作用导致在 Si 纳米膜上的外延生长纳米压电器件的双面有序排列，从而在薄的结晶半导体片中产生空间和周期性变化的应变场。应变对能带结构的固有影响会产生带隙调制，从而有效地创建了一个单元素电子超晶格。相反，足够大的外部施加应变可以使 Ge 成为直接带隙半导体，为 Group IV 元素光源带来了希望。
