The Electronic Properties of O-Doped Pure and Sulfur Vacancy-Defect Monolayer WS2: A First-Principles Study

Abstract

Based on the density functional theory (DFT), the electronic properties of O-doped pure and sulfur vacancy-defect monolayer WS2 are investigated by using the first-principles method. For the O-doped pure monolayer WS2, four sizes (2 × 2 × 1, 3 × 3 × 1, 4 × 4 × 1 and 5 × 5 × 1) of supercell are discussed to probe the effects of O doping concentration on the electronic structure. For the 2 × 2 × 1 supercell with 12.5% O doping concentration, the band gap of O-doped pure WS2 is reduced by 8.9% displaying an indirect band gap. The band gaps in 3 × 3 × 1 and 4 × 4 × 1 supercells are both opened to some extent, respectively, for 5.55% and 3.13% O doping concentrations, while the band gap in 5 × 5 × 1 supercell with 2.0% O doping concentration is quite close to that of the pure monolayer WS2. Then, two typical point defects, including sulfur single-vacancy (VS) and sulfur divacancy (V2S), are introduced to probe the influences of O doping on the electronic properties of WS2 monolayers. The observations from DFT calculations show that O doping can broaden the band gap of monolayer WS2 with VS defect to a certain degree, but weaken the band gap of monolayer WS2 with V2S defect. Doping O element into either pure or sulfur vacancy-defect monolayer WS2 cannot change their band gaps significantly, however, it still can be regarded as a potential method to slightly tune the electronic properties of monolayer WS2.

Recent Advances in Layered Tungsten Disulfide as Electrocatalyst for Water Splitting

“…Similarly, Wang et al [210] also studied the influence of O doping on WS 2 using a theoretical calculation. The calculation results suggested that the relatively high doping concentration would reduce the band gap, while the conclusion was opposite at a relatively low concentration.…”

Electronic and Magnetic Properties of Bulk and Monolayer CrSi2: A First-Principle Study

“…It was consistent with the Hund's rules, that electrons always take precedence of different orbits and have the same spin direction occupying the equivalent orbital. Owing to quantum size and surface effects, two-dimensional (2D) materials may present extensive novel physical and chemical properties, when downsizing from three dimensions to two dimensions or one dimension [20][21][22][23][44][45][46][47]. To further investigate the interrelationship between thickness and magnetism in CrSi2, we also calculated magnetic moment of unit cell of 2D multilayer nanosheets with different layers.…”

“…As the layers increase, the decrease of magnetic moments occurs in CrSi 2 nanosheets. Considering weak van der Waals force and strong chemical bonds between layers, quantum size [20][21][22][23]46] and surface effects [44] occur when downsizing from bilayers to monolayer in CrSi 2 nanosheets. We deduced that the band energy between layers, as well as quantum size and surface effects play an important role in magnetism of materials.…”

“…Contrasting with bulk materials, low-dimensional materials with unusual physical properties are important for potential applications in spintronics [12][13][14][15], magnetic storage [16,17], and molecular scale electronic devices [18,19], etc. Two-dimensional (2D) materials present extensive novel properties due to quantum size effects [20][21][22][23]. The properties of materials strongly depend on the crystal structure.…”

“…Thus, we can change structure phases to tune the properties of materials. Previous investigations have proved that controlling the crystal structure and thickness of materials can tune magnetic moment [20], transform metal to semimetal or semiconductor transition [21], and phase segregation [22], as well as alter electronic properties [23]. Among transition metal silicide, CrSi 2 received numerous attention due to important applications in Si-based device technology [24][25][26].…”