Elastically Relaxed Free-standing Strained-Si Nanomembranes

TL;DR

This paper presents a defect-free method to control strain in silicon nanomembranes through elastic strain sharing, enabling tunable electronic properties without introducing dislocations.

Contribution

It introduces a versatile, defect-free approach to manipulate strain in silicon-based nanomembranes using elastic strain sharing and film transfer techniques.

Findings

X-ray diffraction confirms strain predictions by elasticity theory.

Strain tuning effectively alters electronic properties in quantum wells.

Method avoids defect formation common in traditional strain engineering.

Abstract

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.