文章信息/Info

Title:

Complex Doping of Ga, In and related defect study in caged skuttterudites CoSb3

作者:

席麗麗1; 邱雨婷1; 史訊1; 楊炯2;  陳立東1; 楊繼輝2; 張文清1

1中國科學院上海硅酸鹽研究所，上海 200050 中國
 2美國華盛頓大學，西雅圖，98195-2120美國

Author(s):

Xi Lili1;  Qiu Yuting1;  Shi Xun1;  Yang Jiong2;  Chen Lidong1;  Yang Jihui2;  Zhang Wenqing1

1Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

2University of Washington, Seattle, WA 98195-2120, USA

關鍵詞:

方鈷礦; 第一性原理; 熱電材料; 復雜缺陷結構

DOI:

10.7502/j.issn.1674-3962.2015.01.04

文獻標志碼:

A

摘要:

本文通過第一性原理與熱力學結合的方法，研究了Ga, In等元素摻雜的CoSb3基方鈷礦化合物中的復雜缺陷問題。詳細計算了Ga，In在CoSb3中填充，Co，Sb位置替換以及填充--替換同時共存等缺陷的形成能。研究結果表明, 缺陷形成能與費米能級、化學勢等相關，Ga，In等元素在方鈷礦中不是單純的填充，而是填充和Sb位置替換同時共存的復雜缺陷。Ga摻雜以填充--替換比例2:1的缺陷為主，而In元素摻雜，根據不同的條件可形成填充, 替換, 以及不同比例的填充替換復合缺陷, 其中尤其以4:2和2:1的最多。根據巨正則系宗, 研究了Ga, In摻雜系統的載流子濃度和各缺陷的濃度。 發現Ga, In摻雜的方鈷礦由于填充和替換電荷的自補償效應, 其載流子濃度較低，尤其是Ga填充, 具有類似本證半導體的低載流子濃度，且得到實驗證實。In摻雜系統由于填充替換的比例偏離2:1, 填充位置的In比Ga的稍高一些，因此具有比Ga摻雜更高的載流子濃度。

Abstract:

Complex doping is one of the challenging problems to be understood in doping and the associated structure tuning in materials science. Here we investigate the single-impurity-induced complex doping behaviors of group 13 elements Ga or In in caged skutterudite CoSb3 through a combination of ab initio total-energy calculations and thermodynamics. Formation energies of void filling, Sb-substitution, and complex dual-site occupancy defects with different charge states, and their dependence on chemical potentials of species are considered. Our results show that Ga atoms predominantly form the dual-site 2GaVF-GaSb defects and substitute for Sb only at very high Fermi levels or electron concentrations. Indium atoms, on the other hand, can play multiple roles in skutterudites, including filling in the crystalline voids, substituting for Sb atoms, or forming dual-site occupancy, among which the fully charge-compensated dual-site defects (2InVF-InSb and 4InVF-2InSb) are dominant. The total defect concentrations are studied by using overall charge neutrality under the grand canonical ensemble. The concentration ratio of impurities at void-filling sites and that at Sb-substitution sites for Ga-doped CoSb3 is very close to be 2:1, while this value visibly deviates from 2:1 for In-doped CoSb3. The 2:1 ratio of Ga-doping in CoSb3 causes low electron concentration (~2*1019cm-3) and makes the doped system a semiconductor. The underlying physics of the doping behavior for group 13 elements in CoSb3 is also analyzed.