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Exploration of new direct gap semiconductor Na2X (X = S and Se) monolayers
Applied Surface Science Số , năm 2022 (Tập 606, trang -)
ISSN: 1694332
ISSN: 1694332
DOI: 10.1016/j.apsusc.2022.154809
Tài liệu thuộc danh mục:
Article
English
Từ khóa: Aluminum; Calculations; Density functional theory; Energy gap; Optoelectronic devices; Selenium compounds; Semiconductor doping; Sodium; Stability; Sulfur compounds; Density-functional theory calculations; Direct-gap semiconductor; Doping effects; Electronic and magnetic properties; Enthalpy dispersion curves; First principles; Formation enthalpy; Na2S and na2se monolayer; Prediction-based; Vacancy effects; Monolayers
Tóm tắt tiếng anh
In this work, we report the theoretical prediction, based on density functional theory (DFT) calculations, of new Na2X (X = S and Se) monolayers considering their structural, electronic and magnetic properties. Formation enthalpy and phonon dispersion curves are calculated to examine the structural stability. Na2S and Na2Se single layers are Γ−Γ direct gap semiconductors with energy gaps of 2.17(2.99) and 2.06(2.84) eV, respectively, as determined by standard-PBE (hybrid-HSE06) functional. These two-dimensional (2D) materials are magnetized by creating single Na vacancy, where the magnetic properties are produced mainly by X atoms closest to the defect site. Meanwhile, single X vacancy causes a significant band gap reduction, preserving the paramagnetic nature. Similar effects are observed for oxygen doping, where the energy gap decreases linearly according to increase the doping concentration. In addition, aluminum doping is also efficient to tune this important parameter. It has been found an abrupt reduction once the monolayers are doped with Al atom, however further increasing Al composition will lead to a nearly linear increase. Results presented herein introduce new 2D direct gap semiconductors with band gaps values lying in the visible regime, prospective to be applied in optoelectronic devices, as well as suggest efficient approaches to modify their fundamental properties. © 2022 Elsevier B.V.
