By combining ab initio calculations and experiments, we demonstrate how the band gap of the transition metal trichalcogenide TiS₃ can be modified by inducing tensile or compressive strain. In addition, using our calculations, we predicted that the material would exhibit a transition from a direct to an indirect band gap upon application of a compressive strain in the direction of easy electrical transport. The ability to control the band gap and its nature could have a significant impact on the use of TiS₃ for optical applications. We go on to verify our prediction via optical absorption experiments that demonstrate a band gap increase of up to 9% (from 0.99 to 1.08 eV) upon application of tensile stress along the easy transport direction.

Controlling the strain in two-dimensional (2D) materials is an interesting avenue to tailor the mechanical properties of nanoelectromechanical systems. Here, we demonstrate a technique to fabricate ultrathin tantalum oxide nanomechanical resonators with large stress by the laser oxidation of nano-drumhead resonators composed of tantalum diselenide (TaSe₂), a layered 2D material belonging to the metal dichalcogenides. Before the study of their mechanical properties with a laser interferometer, we verified the oxidation and crystallinity of the freely suspended tantalum oxide using high-resolution electron microscopy. We demonstrate that the stress of tantalum oxide resonators increases by 140 MPa (with respect to pristine TaSe₂ resonators), which causes an enhancement in the quality factor (14 times larger) and resonance frequency (9 times larger) of these resonators.