采用基于密度泛函理论结合投影缀加平面波方法的VASP软件包,在考虑所有掺杂原子构型的前提下,对Cd掺杂ZnO合金的晶格常数、禁带宽度、电子态密度和形成焓进行了计算,分析了Cd含量和掺杂原子构型对纤锌矿wz-Zn1-xCdxO合金的电子结构和结构稳定性的影响.计算结果表明:随着Cd含量的不断增加,纤锌矿ZnCdO合金的平均晶格常数a,c均线性增加,但c/a的比值不会发生显著的变化;纤锌矿ZnCdO合金的能带宽度随着Cd含量增加而减小,满足Eg(x)=3.28-5.04x+4.60x2,与实验结果相符合.但是,不同掺杂原子构型的禁带宽度之间存在比较明显的差异,是ZnCdO合金PL光谱宽化的重要因素之一;Cd掺杂导致纤锌矿ZnCdO合金的导带电子态密度分布整体向低能方向移动,引起带隙宽度变小;Cd的5s电子态是能带窄化的主要贡献;纤锌矿、闪锌矿和熔岩矿三种相结构的ZnCdO合金形成焓对比分析发现:当CdO掺杂比例在0.25-0.75的范围内时,纤锌矿和闪锌矿ZnCdO存在共生的可能;当CdO掺杂比例达到0.75时,ZnCdO合金开始发生从纤锌矿结构到熔岩矿的结构相变.%The VASP (Vienna Ab-initio Simulation Package) based on the density-functional theory (DFT) method combined with projector augmented wave (PAW) method is used to calculate the lattice parameters, band gap, density of states ( DOS), and formation enthalpy of ZnCdO alloy by considering all the doping configurations. The calculation results indicate that the average parameters of wurtzite (wz) Zn1-x Cdx O alloy, a and c, increase linearly, but the ratio of c/a does not change obviously with the increase of Cd content. With increasing Cd content, the band gap is reduced and the variation of band gap can be fitted by Eg (x) = 3.28 - 5.04x + 4.60x2, which is consistent with the experimental results.At a given Cd content, different doping configurations result in different Eg values, being one of the reasons of widening of the photoluminescence spectra of ZnCdO alloy. The DOS of wz-ZnCdO alloy in conduction band is shifted towards the lower energy side after Cd doping, causing the reduction of band gap. The reduction of band gap can be attributed to the contribution of 5s states of Cd. By comparing the formation enthalpy of wz-ZnCdO with those of zinc blende and rocksalt ZnCdO alloys, we find that the wurtzite phase of ZnCdO can coexist with zinc blende phase in the range of Cd content from 0. 25 to 0.75 and will transit to the rocksalt phase at the Cd content of about 0. 80.
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