Computational prediction of two-dimensional group-IV mono-chalcogenides

• Published in: Applied physics letters 2014-07, Vol.105 (4)
• Main Authors: Singh, Arunima K., Hennig, Richard G.
• Format: Article
• Language: English
• Subjects: Applied physics; CHALCOGENIDES; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CONFINEMENT; CRYSTAL STRUCTURE; DENSITY FUNCTIONAL METHOD; Dimensional stability; Dynamic stability; ELECTRICAL PROPERTIES; FORECASTING; FORMATION HEAT; Free energy; Germanium; Heat of formation; Heterostructures; Lead; Mathematical analysis; Molybdenum disulfide; MOLYBDENUM SULFIDES; Optoelectronics; PHONONS; Quantum confinement; Selenium; SEMICONDUCTOR MATERIALS; Sodium chloride; SODIUM CHLORIDES; SOLAR CELLS; SOLAR ENERGY CONVERSION; SPECTRA; STABILITY; Structural stability; Tin; TWO-DIMENSIONAL CALCULATIONS; VAN DER WAALS FORCES
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4891230

Density functional calculations determine the structure, stability, and electronic properties of two-dimensional materials in the family of group-IV monochalcogenides, MX (M = Ge, Sn, Pb; X = O, S, Se, Te). Calculations with a van der Waals functional show that the two-dimensional IV-VI compounds are most stable in either a highly distorted NaCl-type structure or a single-layer litharge type tetragonal structure. Their formation energies are comparable to single-layer MoS2, indicating the ease of mechanical exfoliation from their layered bulk structures. The phonon spectra confirm their dynamical stability. Using the hybrid HSE06 functional, we find that these materials are semiconductors with bandgaps that are generally larger than for their bulk counterparts due to quantum confinement. The band edge alignments of monolayer group IV-VI materials reveal several type-I and type-II heterostructures, suited for optoelectronics and solar energy conversion.