Reversible Control of In-Plane Elastic Stress Tensor in Nanomembranes

The physical properties of materials critically depend on the interatomic distances of the constituent atoms, which in turn can be tuned by introducing elastic strain (stress). While about four decades ago strain was generally regarded as a feature to be avoided in semiconductors,[1] strain engineering is nowadays ubiquitously used, e.g., to enhance the carrier mobility in transistors[2,3] and to achieve lasing action at reduced current densities in heterostructure lasers.[4] For this reason, its potential impact on our society has been compared to that of chemical alloying.[5] Strain can be used not only to enhance specific material/device properties, but also to impart completely new properties to a given material, thus opening the way to previously inaccessible applications. Examples are Ge turning into a direct-band gap semiconductor suitable for lasers,[6-9] exciton dynamics tailoring in nanowires induced by strain gradients,[10] graphene electronic states engineering and strain-induced giant pseudo-magnetic fields up to 300 T,[11,12] a topological insulator turning into a semiconductor,[13] linear electro-optical effects in Si,[14] bandgap modulation in atomically thin films [15] or surface chemical and electronic states tuning.[16]