Elastically Relaxed Free-standing Strained-Si Nanomembranes

摘要

Strain plays a critical role in the properties of materials. In silicon andsilicon-germanium, strain provides a mechanism for control of both carriermobility and band offsets. In materials integra-tion, strain is typically tunedthrough the use of dislocations and elemental composition. We demonstrate aversatile method to control strain, by fabricating membranes in which the finalstrain state is controlled by elastic strain sharing, i.e., without theformation of defects. We grow Si/SiGe layers on a substrate from which they canbe released, forming nanomembranes. X-ray diffraction measurements confirm afinal strain predicted by elasticity theory. The effec-tiveness of elasticstrain to alter electronic properties is demonstrated by low-temperaturelongi-tudinal-Hall effect measurements on a strained-Si quantum well before andafter release. Elastic strain sharing and film transfer offers an intriguingpath towards complex, multiple-layer struc-tures in which each layer'sproperties are controlled elastically, without the introduction of unde-sirabledefects.