Elastically Relaxed Free-standing Strained-Si Nanomembranes

Strain plays a critical role in the properties of materials. In silicon and silicon-germanium, strain provides a mechanism for control of both carrier mobility and band offsets. In materials integra-tion, strain is typically tuned through the use of dislocations and elemental composition. We demonstrate a versatile method to control strain, by fabricating membranes in which the final strain state is controlled by elastic strain sharing, i.e., without the formation of defects. We grow Si/SiGe layers on a substrate from which they can be released, forming nanomembranes. X-ray diffraction measurements confirm a final strain predicted by elasticity theory. The effec-tiveness of elastic strain to alter electronic properties is demonstrated by low-temperature longi-tudinal-Hall effect measurements on a strained-Si quantum well before and after release. Elastic strain sharing and film transfer offers an intriguing path towards complex, multiple-layer struc-tures in which each layer's properties are controlled elastically, without the introduction of unde-sirable defects.

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