Design of opto-electronic properties in two dimensional materials by enhanced flexoelectric coupling.

Electromechanical effects, such as piezo- and flexoelectricity, are a consequence of the coupling of an applied electric field to the strain and the strain gradient, respectively. These effects are expected to be strongly enhanced in two dimensional materials (2D), first, due to the reduction in lattice symmetries in the 2D limit, and second, due to the superior elastic properties, allowing strains even up to 10% in some cases. Furthermore, 2D materials are fully flexible and bendable, thus ushering a new era of flexible opto-electronic devices. In this proposal, we will first investigate the fundamental flexoelectric properties of a wide variety of 2D materials by using a combination of analytical and ab-initio approaches. Important questions related to the magnitude of the coupling coefficients, the effect of phonon anharmonicity and the identification of materials with optimal electro- and mechanical properties will be answered. Subsequently we will model specific strain configurations as out-of-plane (ripples, folds, kirigami) and in-plane geometries (patterned layers, heterostructures, etc.). These are of significant importance because, as opposed to bulk electromechanical effects, modifications at the nanoscale in 2D materials greatly affect their optoelectronic properties. As concrete examples we will investigate the possibility of creating flexotransistors or flexo-photovoltaic devices.

Keywords:OPTO ELECTRONICS

Disciplines:Condensed matter physics and nanophysics, Electronics