Ordered and Disordered Phases in Mo1−xWxS2 Monolayer

Abstract

With special quasirandom structure approach and cluster expansion method combined with first-principle calculations, we explore the structure and electronic properties of monolayer Mo1−xWxS2 alloy with disordered phase and ordered phase. The phase transition from ordered phase to disordered phase is found to happen at 41 K and 43 K for x = 1/3 and x = 2/3, respectively. The band edge of VBM is just related with the composition x, while the band edge of CBM is sensitive to the degree of order, besides the concentration of W. Near the CBM band edge, there are two bands with the Mo-character and W-character, respectively. It is found that in disordered phase the Mo-character band is mixed with the W-character band, while the opposite happens in ordered phase. This result leads to that the splitting of two bands near CBM in ordered phase is larger than in disordered phase and gives rise to the smaller band gap in ordered phase compared to the disordered phase. The electron effective mass in ordered phase is smaller than in disordered phase, while the heavy hole effective mass in ordered phase is larger than that in disordered phase.

Ordered and disordered phases in WS<sub>2(1–</sub><sub><italic>x</italic></sub><sub>)</sub>Se<sub>2</sub><sub><italic>x</italic></sub> monolayer

“…理论上则预测了单层WS 2(1-x) Se 2x 中, 在 Se组分为x=1/3, 1/2和2/3时, 存在有序相 [25] . 之前关于 单层Mo 1-x W x S 2 的有序相和无序相 [26] 的研究发现, Mo [30,31] . 建立 的合金随机结构中, 关于S和Se的关联函数很接近无序 关联函数, 表明采用SQS建立的无序合金结构能很好地 表达实际无序合金的物理特性, 其中, 合金在超胞中的 原子结构如图1所示.…”

Layered Ternary and Quaternary Transition Metal Chalcogenide Based Catalysts for Water Splitting

“…Meanwhile, the Jeon group has reported synthesis of MoS X O y by simple CVD method to modulation of band structures of MoS 2 [68]. The Fan group has analyzed other type of ternary TMCs that contain two type of transition metal, in which they have shown different ordered and disordered phases of Mo 1−x W x S 2 monolayer [63].…”

Layered Ternary and Quaternary Transition Metal Chalcogenide Based Catalysts for Water Splitting

“…Meanwhile, the Jeon group has reported synthesis of MoSXOy by simple CVD method to modulation of band structures of MoS2 [66]. The Fan group has analyzed other type of ternary TMCs that contain two type of transition metal, in which they have shown different ordered and disordered phases of Mo1−xWxS2 monolayer [61].…”

“…However, because the transition metal atoms are generally not adsorption sites for layered TMC materials, many works have suggested that the benefit of double cation TMCs may be more attributable to electron density and local field effects, as illustrated in Figure 8a [61].…”