Vertical strain and twist induced tunability on electronic and optical properties of Janus HfSSe/SnC van der Waals heterostructure

Abstract

To explore the combined advantages of Janus HfSSe and SnC monolayers and find new physics, we construct the HfSSe/SnC vdW heterostructure and investigate its electronic and optical properties in the intrinsic, vertical strained, twisted, and vertical strained-twisted cases, respectively. It is found that the most stable intrinsic heterostructure is a type-II semiconductor with a narrowed band gap, favorably to develop excellent photovoltaic materials and opto-electronic devices. Particularly, its infrared absorption can be greatly enhanced by four orders of magnitude compared to monolayers, with a very high solar energy converting efficiency. However, heterostructures with both HfSSe/SnC and HfSeS/SnC configurations possess different electronic and optical properties due to asymmetrically intrinsic surface dipoles in Janus monolayers. The vertical compression on heterostructure can further reduce its band gap and significantly enhance light absorption in the visible and infrared region. Twisting bilayer does not alter the type of band alignment, but holds very significant effects on the band structure in the proximity of the Fermi level, thus influencing the transport behaviors of heterostructure. And further forming a twisted-vertical strained structure, we find that its band gap and types as well as band alignment manner are likely changed substantially due to orbital hybridization strengthened.