First‐principles investigation of the (HfSe₂)_4−n–(HfSSe)_n (n = 0, 1, 2, 3, 4) lateral heterostructures

Abstract

In this work, we investigate the structural, electronic, and optical properties of the HfSe2 and Janus HfSSe monolayers, and their lateral heterostructures (LHSs) (HfSe2)4−n–(HfSSe)n (n = 1, 2, and 3) using first‐principles calculations. Stability of these two‐dimensional (2D) materials is examined through phonon dispersion curves and cohesive energy. Besides, small heat of formation suggests the feasibility of experimental synthesis of the LHSs. Calculated electronic band structures indicate an indirect gap semiconductor nature of all materials at hand, where the energy gap decreases slightly from (HfSe2)4–(HfSSe)0 to (HfSe2)0–(HfSSe)4 as a result of the increase of Coulomb effect. Moreover, the LHSs formation makes possible the indirect–direct gap transition, which can be achieved by applying proper external strain to the lattice. Energy gap of the H22‐system shows a strong strain‐dependence, increasing with tensile strain and decreasing with compressive strain. The semiconductor–metal transition may be induced at strain strengths of −6% and −8%. Optical calculations indicate a wide absorption band from visible to ultraviolet regime with large absorption coefficient. Our findings introduce new 2D LHSs with tunable properties for application in optoelectronic nano devices.

Exploring the ZrXO (X = S and Se) Janus Monolayers for Optoelectronic and Spintronic Applications

“…[13][14][15] Besides, the ZrSSe Janus has been also investigated, following the success of MoSSe monolayers [16,17] and other TMDs Janus structures. [18][19][20] For instance, Tuan et al [21] have examined the electronic and optical properties of the ZrSSe monolayer using first-principles calculations. Results assert the indirect gap semiconductor behavior with an energy gap of 1.341 eV calculated by the hybrid functional, this parameter can be effectively modulated by the external strain to induce the semiconductor-to-metal transition at a strain strength of 7%.…”