Static and dynamic elastic strain engineering of low-dimensional optically active ceramics

Abstract

I explored both static van der Waals epitaxial strain engineering and phase transition induced dynamic strain pathways that could enable a much broader horizon of the elastic strain engineering field. By taking advantage of multiple vapor deposition methods, I obtained various optically active semiconductors including halide perovskite, lead iodide and cadmium sulfide whose strain and strain-induced property changes could be revealed by optical characterization. In the context of van der Waals strain engineering, by taking advantage of the mechanically soft halide perovskite grown on mica substrate, surprisingly we found that significant strain could be present at the van der Waals interface, which is large enough to alter the material’s intrinsic properties. The van der Waals interaction could further guide the growth behavior of halide perovskite and render a one dimensional nanowire network. In another perspective, strongly correlated VO2 was used as a template for the purpose of dynamic strain engineering. It is shown that within the metal-insulator transition of VO2, a non-linear response of the coating semiconductor can be observed, a direct evidence of dynamics strain engineering. For a better application of the dynamics strain engineering idea, a novel substrate consisting of vertically aligned VO2 nanowires was developed. The VO2 nanoforest serve as a possible strategy towards the realization of significant strain at bulk. As a summary of the whole dissertation, our experimental endeavor sheds light on the new possibilities in the field of strain engineering on emergent material systems.

Elastic strain engineering has long been considered as an effective way to enhance and edit intrinsic properties of semiconductors. In the field of group IV and III-V materials, significant progresses have already been made in devices comprised of elastically strained materials. However, the existing strain engineering which mainly deals with the static epitaxial chemical strain could not cater to the rapid growth and addition of promising material families due to the lack of proper substrates and the limited strain amplitudes. In this dissertation, I hope to fundamentally understand the relation between semiconducting property and novel heterogeneous material interface.