Layered post-transition-metal dichalcogenide SnGe2N4 as a promising photoelectric material: a DFT study

• Published in: RSC advances Vol. 12; no. 17; pp. 10249 - 10257
• Main Authors: Dat, Vo D, Vu, Tuan V
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 31.03.2022; The Royal Society of Chemistry
• Subjects: Chalcogenides; Chemistry; Compressive properties; Conduction bands; Density of states; Electric field strength; Electric fields; Electron mobility; Electronic structure; Energy gap; First principles; Hole mobility; Infrared radiation; Lattice parameters; Mechanical properties; Modulus of elasticity; Photoelectricity; Poisson's ratio; Tensile strain; Thermal stability; Transition metal compounds; Valence band
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d2ra00935h

First-principles calculations were performed to study a novel layered SnGe2N4 compound, which was found to be dynamically and thermally stable in the 2H phase, with the space group P6m2 and lattice constant a = 3.143 Å. Due to its hexagonal structure, SnGe2N4 exhibits isotropic mechanical properties on the x–y plane, where the Young’s modulus is 335.49 N m−1 and the Poisson’s ratio is 0.862. The layered 2H SnGe2N4 is a semiconductor with a direct band gap of 1.832 eV, allowing the absorption of infrared and visible light at a rate of about 104 cm−1. The DOS is characterized by multiple high peaks in the valence and conduction bands, making it possible for this semiconductor to absorb light in the ultraviolet region with an even higher rate of 105 cm−1. The band structure, with a strongly concave downward conduction band and rather flat valence band, leads to a high electron mobility of 1061.66 cm2 V−1 s−1, which is substantially greater than the hole mobility of 28.35 cm2 V−1 s−1. This difference in mobility is favorable for electron–hole separation. These advantages make layered 2H SnGe2N4 a very promising photoelectric material. Furthermore, the electronic structure of 2H SnGe2N4 responds well to strain and an external electric field due to the specificity of the p–d hybridization, which predominantly constructs the valence bands. As a result, strain and external electric fields can efficiently tune the band gap value of 2H SnGe2N4, where compressive strain widens the band gap, meanwhile tensile strain and external electric fields cause band gap reduction. In particular, the band gap is decreased by about 0.25 eV when the electric field strength increases by 0.1 V Å−1, making a semiconductor–metal transition possible for the layered SnGe2N4.