Polarization-resolved and helicity-resolved Raman spectra of monolayer XP₃ (X = Ge and In)

Abstract

Monolayer XP3 (X=Ge, In) is a theoretically predicted two-dimensional (2D) material with fascinating adsorption efficiency, foreshadowing its potential applications in the photovoltaic and optoelectronic communities. To achieve a comprehensive understanding...

The direct Z-scheme character and roles of S vacancy in BiOCl/Bi2S3-(001) heterostructures for superior photocatalytic activity: a hybrid density functional investigation

“…1(b), in Bi 2 S 3 , there are two nonequivalent Bi sites and three nonequivalent S sites, which are all located at 4c Wyckoff positions of space group Pbnm, and are denoted as Bi1, Bi2, S1, S2, and S3 with blue, cyan, orange, gray and pink colors, respectively. 37,38 In order to evaluate the stability of three possible cases for S vacancy, the defect formation energies (E f ) under different circumstances are calculated using the following equations: [39][40][41]…”

Defect physics of intrinsic point defects in BiPO4 photocatalysts: a hybrid functional study

“…This means that only the À3 charge state is stable for the Bi vacancy defect. In contrast, all O-type vacancies (including V O1 , V O2 , V O3 , and V O4 ) exhibit 0 and +2 charge states, presenting an unusual negative U-centered behavior 42,54 in Fig. 3.…”

“…Since there is one type of Bi atom, one type of P atom, and four nonequivalent O atoms (denoted as O1, O2, O3, and O4) in BiPO 4 , therefore, in principle, there are 21 intrinsic point defects, including six kinds of vacancies (V Bi , V P , V O1 , V O2 , V O3 , and V O4 ), three kinds of interstitials (Bi i , P i , and O i ), and twelve kinds of antisites (Bi P , P Bi , Bi O1 , Bi O2 , Bi O3 , Bi O4 , O Bi , P O1 , P O2 , P O3 , P O4 , and O P ). However, as a result of the previous calculations in BiOCl and Bi 2 O 3 , 15,54 it is challenging to form anti-substitution defects between Bi and O, most likely due to the very different physicochemical properties (mainly electronegativity and atomic radius) between metal Bi and non-metal O. Therefore, here, we do not consider anti-substitutions between Bi and O atoms and only 16 kinds of intrinsic defects in BiPO 4 , are investigated.…”

“…In contrast, as the Bi vacancies easily provide p-type carriers, they simultaneously could become the active sites of the photocatalytic reactions because of its dominant À3 charge state. For the O vacancy defect, because of its deeper charge transition energy level from 0 to +2 charge states, the ionization of the O vacancies is difficult under ambient conditions, 54 and the neutral O vacancies are primary under Opoor conditions. Fig.…”