摘要
作为一种新型的二维材料,蓝磷因其具有较高的载流子迁移率和较大的禁带宽度引起了研究者们极大的研究兴趣.近年来已有研究讨论了蓝磷中的结构缺陷,但是关于其缺陷带电性质的研究尚未见报道.本文利用基于密度泛函理论的第一性原理计算,讨论了蓝磷SW(Stone Wales)缺陷、单空位(SV)缺陷、两种双空位缺陷(DV-1和DV-2)以及两种替位缺陷(OP和CP)的带电性质.利用带电缺陷体系能量依赖于晶胞尺寸的渐进表达式进行外推的方法,修正了蓝磷带电缺陷体系的形成能.研究结果表明,在所讨论的缺陷中,富O条件下Op具有最低的形成能,最稳定;而SV的离化能最小,最容易电离.引入的缺陷态会对蓝磷的禁带宽度产生影响.缺陷带电过程中,缺陷态位置变化导致绝大部分缺陷转变为深能级缺陷.本研究结果对缺陷工程在二维材料上的应用提供了一定的理论指导.
Abstract
As a new two-dimensional material,blue phosphorus has attracted considerable research interest due to its high carrier mobility and large bandgap.Although the structural defects of blue phosphorus have been discussed recently,the charged properties of these defects have not been explored.In this paper,using first-principles calculations based on density functional theory,the six most stable point defects and their corresponding charged states in blue phosphorus are studied,including Stone Wales(SW),single vacancy(SV),two double-vacancy(DV-1 and DV-2)and two substitution defects(Op and CP).The converged ionization energy values of charged defects in blue phosphorus are obtained by extrapolating the asymptotic expression of the energy dependent on the cell size.Subsequently,the formation energy values for different charge states are modified to determine their structural stabilities.Finally,their electronic properties are analyzed through band structures.The results suggest that SV1-is easy to ionize,owing to its lowest ionization energy(1.08 eV).Furthermore,among the defects we are considering,OP1-is the most stable charged defect in blue phosphorus,with the lowest formation energy(-9.33 eV)under O-rich chemical potential condition.The negative formation energy indicates that O atoms can exist stably in blue phosphorus,implying that blue phosphorus is easily oxidized.The introduction of defect states will affect the bandgap of blue phosphorus,and the ionization of defects will cause the defect energy levels to shift,leading defects to transition between shallow and deep levels.This study provides theoretical guidance for the application of defect engineering in two-dimensional materials.
维普
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