Prediction of hydrogenated group IV–V 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, $${\hbox {Sn}}_2{\hbox {Bi}}$$ Sn 2 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 $${\hbox {Sn}}_2{\hbox {Bi}}$$ Sn 2 Bi , namely $${\hbox {Si}}_2{\hbox {P}}$$ Si 2 P , $${\hbox {Si}}_2{\hbox {As}}$$ Si 2 As , $${\hbox {Si}}_2{\hbox {Sb}}$$ Si 2 Sb , $${\hbox {Si}}_2{\hbox {Bi}}$$ Si 2 Bi , $${\hbox {Ge}}_2{\hbox {P}}$$ Ge 2 P , $${\hbox {Ge}}_2{\hbox {As}}$$ Ge 2 As , $${\hbox {Ge}}_2{\hbox {Sb}}$$ Ge 2 Sb , and $${\hbox {Ge}}_2{\hbox {Bi}}$$ Ge 2 Bi . The cohesive energies, phonon dispersions, and AIMD calculations show that, similar to $${\hbox {Sn}}_2{\hbox {Bi}}$$ Sn 2 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 $${\hbox {Si}}_2{\hbox {YH}}_2$$ Si 2 YH 2 and $${\hbox {Ge}}_2{\hbox {YH}}_2$$ Ge 2 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 $${\hbox {Si}}_2{\hbox {SbH}}_2$$ Si 2 SbH 2 and $${\hbox {Si}}_2{\hbox {BiH}}_2$$ Si 2 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.

Thermoelectric characteristics of X$$_2$$YH$$_2$$ monolayers (X=Si, Ge; Y=P, As, Sb, Bi): a first-principles study

“…The lattice thermal conductivity follows the expected trend with increasing the atomic mass. More specifically, Si BiH and Ge BiH have the lowest thermal conductivity of 0.09 Wm K at 300 K. This is due to their lower Debye temperature, smaller phonon group velocity, and stronger anharmonicity compared to other monolayers as discussed in the previous work 33 . Also, Si SbH and Ge SbH exhibit very low thermal conductivity of 0.12 Wm K .…”

“…All the structural parameters are listed in Table 1 . The structural, dynamical, and thermal stabilities of the monolayers were already validated by cohesive energy, phonon dispersion, and ab-initio molecular dynamics (AIMD) analyses in previous work 33 . We also calculated the formation energies through: where is the total energy of monolayer, is the energy of a single atom X ( Y ) of the bulk structure, and is the ground state energy of a hydrogen molecule.…”

“…Inspired by these results, in our previous work 33 , for the first time, we introduced and investigated a new class of 2D binary monolayers with an empirical formula of X Y, where X and Y are selected from group-IV (Si and Ge) and V (P, As, Sb, and Bi), respectively, including Si P, Si As, Si Sb, Si Bi, Ge P, Ge As, Ge Sb, and Ge Bi. We found that the pure X Y monolayers are unstable metals owing to the dangling bonds of X atoms.…”

“…In our previous study 33 , it was discussed that to compensate the octet rule, X (Si and Ge) atoms should adsorb hydrogen. Different hydrogenation structures were considered.…”

Functionalized few-layer silicene nanosheets: density functional theory on stability, structural, and electronic properties

“…This behavior has been found in some theoretical investigations of 2D materials, and has been generally associated with the difficulty in converging the out-of-plane ZA transverse acoustic mode. 17,47 We computed the elastic constants of the systems with Eq. have Poisson ratio ν between 0.17 and 0.30, in the 0-0.5 range which has been observed in 2D materials 39 and isotropic systems.…”