Prediction of hydrogenated group IV\u2013V hexagonal binary monolayers

Abstract

Group IV and V monolayers are very crucial 2D materials for their high carrier mobilities, tunable band gaps, and optical linear dichroism. Very recently, a novel group IV–V binary compound, {hbox {Sn}}_2{hbox {Bi}}, has been synthesized on silicon substrate, and has shown very interesting electronic properties. Further investigations have revealed that the monolayer would be stable in freestanding form by hydrogenation. Inspired by this, by means of first-principles calculations, we systematically predict and investigate eight counterparts of {hbox {Sn}}_2{hbox {Bi}}, namely {hbox {Si}}_2{hbox {P}}, {hbox {Si}}_2{hbox {As}}, {hbox {Si}}_2{hbox {Sb}}, {hbox {Si}}_2{hbox {Bi}}, {hbox {Ge}}_2{hbox {P}}, {hbox {Ge}}_2{hbox {As}}, {hbox {Ge}}_2{hbox {Sb}}, and {hbox {Ge}}_2{hbox {Bi}}. The cohesive energies, phonon dispersions, and AIMD calculations show that, similar to {hbox {Sn}}_2{hbox {Bi}}, all of these freestanding monolayers are stable in hydrogenated form. These hydrogenated monolayers are semiconductors with wide band gaps, which are favorable for opto-electronic purposes. The {hbox {Si}}_2{hbox {YH}}_2 and {hbox {Ge}}_2{hbox {YH}}_2 structures possess indirect and direct band gaps, respectively. They represent very interesting optical characteristics, such as good absorption in the visible region and linear dichroism, which are crucial for solar cell and beam-splitting devices, respectively. Finally, the {hbox {Si}}_2{hbox {SbH}}_2 and {hbox {Si}}_2{hbox {BiH}}_2 monolayers have suitable band gaps and band edge positions for photocatalytic water splitting. Summarily, our investigations offer very interesting and promising properties for this family of binary compounds. We hope that our predictions open ways to new experimental studies and fabrication of suitable 2D materials for next generation opto-electronic and photocatalytic devices.