Abstract
Two-dimensional (2D) materials present a new class of materials whose structures and properties can differ from their bulk counterparts. We perform a genetic algorithm structure search using density-functional theory to identify low-energy structures of 2D group-IV dioxides (, Ge, Sn, Pb). We find that 2D is most stable in the experimentally determined bi-tetrahedral structure, while 2D and are most stable in the structure. For 2D , the genetic algorithm finds a new low-energy 2D structure with monoclinic symmetry. Each system exhibits 2D structures with formation energies ranging from 26 to 151 meV/atom, below those of certain already synthesized 2D materials. The phonon spectra confirm their dynamic stability. Using the HSE06 hybrid functional, we determine that the 2D dioxides are insulators or semiconductors, with a direct band gap of 7.2 eV at for 2D , and indirect band gaps of 4.8–2.7 eV for the other dioxides. To guide future applications of these 2D materials in nanoelectronic devices, we determine their band-edge alignment with graphene, phosphorene, and single-layer BN and . An assessment of the dielectric properties and electrochemical stability of the 2D group-IV dioxides shows that 2D and are particularly promising candidates for gate oxides and 2D also as a protective layer in heterostructure nanoelectronic devices.
- Received 7 November 2016
DOI:https://doi.org/10.1103/PhysRevB.95.155426
©2017 American Physical Society
Physics Subject Headings (PhySH)
Synopsis
A Crystal Ball for 2D Materials
Published 18 April 2017
Researchers predict new two-dimensional materials whose structures differ from their three-dimensional counterparts.
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