Straining Two Dimensional Materials

Abstract

Two dimensional materials are atomically or molecularly thin materials that extend macroscopically. By mechanically probing these two dimensional materials the mechanical, thermal, and optical nature of these materials are probed in this dissertation. The coefficient of thermal expansion of graphene is measured and shown to be negative, in agreement with predictions from soft condensed matter. Also the adhesion of graphene to a substrate is shown to be temperature dependent. Through strain engineering another two dimensional material, MoS2, it is shown that its band gap is strain dependent. Strain also transitions this material from a direct band gap to an indirect band gap material at strains of approximately 1.6%. Finally, graphene is shown to behave as a two dimensional entropic spring, with an in-plane stiffness as low as 50N/m.