Formation of 2D GaXY (X = S, Se; Y = F, Cl, Br, I) with enhanced piezoelectricity via decomposition of Ga-monochalcogenide by halogenation

Abstract

Motivated by the excellent electronic and optoelectronic properties of two-dimensional (2D) Ga-monochalcogenides, we systematically investigated the effect of halogenation on physical properties of monolayer GaX (X = S, Se) by the first-principles calculations. Crystal lattices of GaX were decomposed with the halogen atom being absorbed on top of the Ga atom. Unexpectedly, a series of monolayer GaXY (X = S, Se; Y = F, Cl, Br, I) was formed. Except for GaXF, other monolayer GaXY has good structural stability at room temperature. With the broken mirror symmetry, monolayer GaXY has superior flexibility, a direct bandgap in the range of 0.78–4.43 eV, the intrinsic vertical polarization, and larger in-plane as well as out-of-plane piezoelectric coefficients than Ga-monochalcogenides. Moreover, by comparing the structural stability and side-dependent electronic band alignment, we concluded that monolayer GaXY (X = S, Se; Y = Cl, Br) is suitable for photocatalytic water-splitting applications.

Strong Vertical Piezoelectricity and Broad-pH-Value Photocatalyst in Ferroelastic Y2Se2BrF Monolayer

“…The potential difference Δ E C (Δ E V ) between E CBM vac ( E VBM vac ) and reduction potential (oxidation potential) is widely viewed as the driving force for the HER (OER) process, − calculated by normalΔ E C = E C B M v a c − E normalH + / normalH 2 normalΔ E V = E normalH 2 normalO / normalO 2 − E V B M v a c The values of Δ E C and Δ E V are summarized in Table . The Δ E C values (0.75–1.79 eV) of Y 2 Se 2 XX′ monolayers are larger than those of PtSSe (Δ E C = 0.44 eV), GaSeBr (Δ E C = 0.52 eV), and LiGaTe 2 (Δ E C = 0.58 eV) . Meanwhile, the Δ E V values (0.99–1.37 eV) of Y 2 Se 2 XX′ monolayers outperform those of MoSSe (Δ E V = 0.65 eV), SnN 3 (Δ E V = 0.34 eV), and GeSe (Δ E V = 0.83 eV) .…”

“…The potential difference Δ E C (Δ E V ) between E CBM vac ( E VBM vac ) and reduction potential (oxidation potential) is widely viewed as the driving force for the HER (OER) process, − calculated by The values of Δ E C and Δ E V are summarized in Table . The Δ E C values (0.75–1.79 eV) of Y 2 Se 2 XX′ monolayers are larger than those of PtSSe (Δ E C = 0.44 eV), GaSeBr (Δ E C = 0.52 eV), and LiGaTe 2 (Δ E C = 0.58 eV) . Meanwhile, the Δ E V values (0.99–1.37 eV) of Y 2 Se 2 XX′ monolayers outperform those of MoSSe (Δ E V = 0.65 eV), SnN 3 (Δ E V = 0.34 eV), and GeSe (Δ E V = 0.83 eV) .…”