Defect formation and carrier compensation in layered oxychalcogenide La<sub>2</sub>CdO<sub>2</sub>Se<sub>2</sub>: an insight from first principles
Defect formation and carrier compensation in layered oxychalcogenide La<sub>2</sub>CdO<sub>2</sub>Se<sub>2</sub>: an insight from first principles
复制标题
层状氧硫族化物La<sub>2</sub>CdO<sub>2</sub>Se<sub>2</sub>中的缺陷形成和载流子补偿：来自第一原理的见解
DOI：
10.1039/d2tc03836f
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发表时间：
2022
影响因子：
6.4
通讯作者：
Oba Fumiyasu
中科院分区：
文献类型：
--
作者：
Gake Tomoya;Kumagai Yu;Takahashi Akira;Hiramatsu Hidenori;Oba Fumiyasu
层状氧硫属化物La 2CdO 2Se 2是n型透明导电材料的候选物，但迄今为止已报道了未掺杂和施主掺杂的La 2CdO 2Se 2的电绝缘性质。在这项研究中，我们调查本征缺陷和非本征掺杂的La 2CdO 2Se 2使用第一性原理计算的基础上的Heyd-Scuseria-Ernzerhof混合功能的方法。计算得到的能带结构和有效质量均呈现二维特征，反映了层状结构。本征缺陷的能量学表明，带负电荷的Cd空位和带正电荷的Cd空位分别在高和低费米能级位置占主导地位。这些缺陷的平衡与Cd的不足和过剩导致的平衡费米能级的中间间隙的位置，这解释了实验报道的近化学计量和电绝缘行为的未掺杂的La 2CdO 2Se 2。在选自I族至IV族元素的各种掺杂剂中，Cd位点处的Al形成浅施主能级，并且La位点处的Sr形成浅受主能级。然而，由这些掺杂剂产生的载流子严重补偿与相反的符号，与施主掺杂的La 2CdO 2Se 2的绝缘性能的报告一致的原生缺陷充电。有人建议，La 2CdO 2Se 2是容易形成镉空位和晶体相比，锌-硒化镉，它具有类似的局部结构的硒化物层在La 2CdO 2Se 2，部分是因为一个灵活的结构弛豫与其二维晶体结构。对非铜基氧硫属化物La_2CdO_2Se_2中缺陷性质的深入了解，对进一步发展透明导电材料的设计原则具有重要意义。
Layered oxychalcogenide La2CdO2Se2 is a candidate for an n-type transparent conductive material, but electrical insulating properties have hitherto been reported for both undoped and donor-doped La2CdO2Se2. In this study, we investigate native defects and extrinsic dopants in La2CdO2Se2 using first-principles calculations based on the Heyd–Scuseria–Ernzerhof hybrid functional approach. The calculated band structure and effective masses show two-dimensional characteristics, reflecting the layered structure. The energetics of the native defects indicates that negatively charged Cd vacancies and positively charged Cd interstitials are dominant at high and low Fermi level positions, respectively. The balance of these defects associated with Cd deficiency and excess leads the equilibrium Fermi level to a mid-gap position, which explains the experimentally reported nearly stoichiometric and electrical insulating behavior of undoped La2CdO2Se2. Among various dopants selected from group-I to IV elements, Al at the Cd site forms a shallow donor level, and Sr at the La site forms a shallow acceptor level. However, the carriers generated by these dopants are severely compensated by the native defects charged with the opposite sign, consistent with the reported insulating properties of donor-doped La2CdO2Se2. It is suggested that La2CdO2Se2 is prone to form Cd vacancies and interstitials compared to zinc-blende CdSe, which has a similar local structure to the selenide layer in La2CdO2Se2, partly because of a flexible structural relaxation related to its two-dimensional crystal structure. Such a detailed understanding of the defect properties in the non-Cu-based oxychalcogenide La2CdO2Se2 is meaningful for further developing design principles for transparent conductive materials.