Edge preference and band gap characters of MoS2 and WS2 nanoribbons

Structure, stability, electronic structure and magnetic property of MoS2 and WS2 nanoribbons are studied based on density functional theory. Formation enthalpies of nanoribbons with a series of widths are calculated and the formation enthalpy versus width curve of zigzag nanoribbon is lower than that of armchair nanoribbon. Edge energy (energy required to create one unit of edge length), which can be regarded as a 1D analog of surface energy (energy required to create one unit of surface area), is defined. For both MoS2 and WS2, zigzag edge energy is always smaller than armchair edge energy, indicating zigzag edge is more preferable than, armchair edge. Band structure calculations show that all zigzag MoS2 and WS2 nanoribbons are magnetic and metallic, except for the narrowest monolayer MoS2 nanoribbon with a width of 0.36 nm, which is a magnetic semiconductor. MoS2 and WS2 nanoribbons with armchair edge keep the semiconducting character of their 2D and 3D counterparts. The effect of nanoribbon width as well as layer thickness to the band gap characters is investigated. (C) 2016 Elsevier B.V. All rights reserved.