Effect of biaxial strain on electronic and optical properties of vertically stacked HfS2/HfSe2 heterostructures

Abstract The structural, electronic, and optical properties of HfS 2 /HfSe 2 heterostructures (HSs) have been investigated using Density Functional Theory. The HfS 2 and HfSe 2 monolayers with H and T phases with different stacking configurations were considered for the formation of HSs. HfS 2 (1T)/HfSe 2 (2H) is found to be the most stable HS as compared to other phases. All phases of HSs show indirect band-gaps HfS 2 (1T) (2.07 eV), HfSe 2 (2H) (1.63 eV), and HfS 2 (1T)/HfSe 2 (2H) (1.44 eV) with valence band (VB) of HS dominated by HfS 2 (1T) and the conduction band (CB) dominated by HfSe 2 (2H) leading to type-II configuration. The optical properties of HS show ab-sorption peaks in the visible region of 420–430 nm with an absorption coefficient of 1.82–1.89 × 10 5 cm −1 . Further, the stability of the HS increases with tensile strain and decreases with compressive strain. Similarly, the band gap increases from 1.44 eV to 1.51 eV with the tensile strain and decreases to 1.30 eV with compressive strain. The tunability of electronic band gap and band alignment of Hf-based HSs by external strain makes them useful for possible use in futuristic optoelectronic devices.