Tailoring the In-plane Stress Tensor in Nanomembranes for Elastic Strain Engineering

The strain state of solid state materials governs their intrinsic physical properties [1]. In recent years, there has been a growing interest in elastic strain engineering of materials for applications on many research fields such as topological insulators [2], nanophotonics [3], spintronics [4] and 2D materials [5], among others. Nevertheless, all the technological approaches used so far are based on the application of static stress fields which limits its possibilities for practical applications and fundamental studies on crystalline materials. In this work, we demonstrate for the first time a novel class of micro-machined piezoelectric actuators capable of exerting reversible in-plane stress fields on demand in semiconductor nanomembranes [6,7]. Our technological approach is based on a legged micro-machined piezoelectric substrate where a GaAs semiconductor nanomembrane is bonded (Fig. 1). The GaAs PL signal measured at the central gap between the legs is used as a probe in order to obtain the stress state of the nanomembrane through a least-square minimization algorithm based on the 8-band k.p theory and the dipole approximation. We show that by applying the appropriate combination of voltages on each of the legs, full control of the in-plane stress field magnitude, angle and anisotropy can be achieved. These results pave the way towards the exploitation of elastic strain engineering in nanomaterials in a way never realized before.