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]