Engineering 2D monolayer structures in II-V binary Zintl-phase compounds ZnX (X = As, Sb, Bi)

Recently, two-dimensional (2D) materials have become an intriguing material because of its numerous applications in spintronics, optoelectronics, and sensing. We present the engineering of 2D monolayer structures in the orthorhombic compounds ZnX (X = As, Sb, Bi) that belong to the space group pbca using density functional theory (DFT). We showed the stability of the 2D monolayer (ML) structures on such materials based on i) the exfoliation energy criterion and ii) the phonon dispersion curve with the absence of imaginary modes. Our calculations on electronic band structures indicate the semiconducting nature of all the ML structures with a sizable bandgap of 1.52 eV (indirect), 0.94 eV (direct), and 0.63 eV (direct) in ZnX with X = As, Sb, and Bi respectively with decreasing trend of the forbidden gap with increasing size of electronegative X-atom. Surprisingly, the electronic properties of ZnBi change while going from metallic bulk to semiconducting monolayer. Our theoretical results on the monolayers of ZnX will pave the way for other theoretical and experimental researchers for further investigations.