硒掺杂锗碲相变存储材料的第一性原理研究

方治乾; 缪奶华; 周健

doi:10.13700/j.bh.1001-5965.2017.0332

硒掺杂锗碲相变存储材料的第一性原理研究

doi: 10.13700/j.bh.1001-5965.2017.0332

方治乾¹,
缪奶华^{1, 2},
周健^{1, 2, ,}

1.
北京航空航天大学材料科学与工程学院, 北京 100083
2.
北京航空航天大学国际交叉科学研究院集成计算材料工程中心, 北京 100083

基金项目:

国家自然科学基金 61274005

详细信息

作者简介:
方治乾  男, 硕士研究生。主要研究方向:相变存储材料

缪奶华  男, 博士, 副教授, 硕士生导师。主要研究方向:计算材料学、相变存储材料、热电材料

周健  男, 博士, 副教授, 硕士生导师。主要研究方向:计算材料学、相变存储材料、热电材料

通讯作者:
周健, E-mail: jzhou@buaa.edu.cn

中图分类号: TB34;O474
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出版历程
- 收稿日期: 2017-05-18
- 录用日期: 2017-06-12
- 网络出版日期: 2018-05-20

First-principles study of Se doped GeTe phase-change material

FANG Zhiqian¹,
MIAO Naihua^{1, 2},
ZHOU Jian^{1, 2
, ,}

1.
School of Material Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
2.
Center for Integrated Computational Materials Engineering, International Research Institute for Multidisciplinary Science, Beijing University of Aeronautics and Astronautics, Beijing 100083, China

Funds:

National Natural Science Foundation of China 61274005

More Information

Corresponding author: ZHOU Jian, E-mail: jzhou@buaa.edu.cn

摘要

摘要:
硒（Se）掺杂可以大幅提高锗碲（GeTe）相变存储材料的再结晶温度，使其具有更高的服役温度和更好的数据保持力，然而Se掺杂对GeTe微观结构和电学性质的影响机制尚不清楚。采用第一性原理计算方法，对Se掺杂GeTe相变存储材料的几何构型、成键性质和电子性质进行了理论研究。结果表明，对于GeTe完美晶体，掺杂的Se原子优先取代Te原子。而对含本征Ge空位的GeTe体系，Se倾向于取代与Ge空位最近邻的Te原子。Se原子与Ge空位具有吸引作用，抑制了Ge空位的移动，从而提高其再结晶温度。Se掺杂导致含Ge空位的菱方相体积收缩，带隙减小，而使含Ge空位的面心立方相体积膨胀，带隙增大。Se掺杂减小了GeTe两晶相的体积差异。计算结果为解释实验中Se掺杂导致的奇特相变性质提供了重要线索。
- Se掺杂GeTe /
- Ge空位 /
- 相变存储材料 /
- 第一性原理计算 /
- 元素掺杂
Abstract:
Doping Se can significantly improve the recrystallization temperature of GeTe phase-change material according to recent experiments, endowing GeTe with a higher working temperature and better data retention. However, the impact of Se on the structure and electrical properties of GeTe is not clear. In this paper, we investigated the effect of Se on the microstructure, bonding characters and electrical properties of crystalline GeTe using first-principles calculation. The results show that the doping Se atom prefers to replace Te in ideal GeTe, while for GeTe systems with intrinsic Ge vacancies, Se tends to replace the Te atoms which are the nearest neighbors of Ge vacancy. The attraction between Se atom and Ge vacancies hinders the movement of Ge vacancies, and thus increases the recrystallization temperature. Furthermore, a shrink of lattice volume and a small reduction of band gap are found in rhombohedral GeTe with Ge vacancies through doping Se, while in face-centered cubic GeTe with Ge vacancies, Se doping causes an expansion in lattice volume and an increase in band gap. Doping Se reduces the volume discrepancy between the two crystalline phases. The calculation results provide clues for explaining the unique phase transformation phenomena of Se doped phase-change materials.
- Se doped GeTe /
- Ge vacancy /
- phase-change materials /
- first-principles calculation /
- elemental doping

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图 1 GeTe晶体结构

Figure 1. Crystalline structure of GeTe

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图 2 完美GeTe晶体掺杂前后在(100)面上的ELF截面图(等高线间隔为0.14)

Figure 2. ELF contour plots on (100) plane for Se doped ideal GeTe crystal (interval is 0.14)

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图 3 Se掺杂Ge₃₁Te₃₂菱方相和Ge₃₁Te₃₂面心立方相的形成能随Se原子与Ge空位之间距离的变化

Figure 3. Formation energy of Se doping in rhombohedral Ge₃₁Te₃₂ and fcc Ge₃₁Te₃₂ versus distance between doped Se atom and Ge vacancy

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图 4 Se掺杂GeTe的2种构型

Figure 4. Two configurations of Se doped GeTe

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图 5 Se掺杂含Ge空位的GeTe体系的在(100)面上的ELF截面图(等高线间隔为0.12)

Figure 5. ELF contour plots on (100) plane for Se doped GeTe systems with intrinsic Ge vacancy (interval is 0.12)

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图 6 菱方相和面心立方相总态密度

Figure 6. Total density of states for rhombohedral phase and fcc

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图 7 菱方相Ge₃₂Te₃₁Se₁和面心立方相Ge₃₂Te₃₁Se₁ Ge原子、Te原子和Se原子的分波态密度

Figure 7. Partial density of states for Ge atom, Te atom and Se atom in rhombohedral Ge₃₂Te₃₁Se₁ and fcc Ge₃₂Te₃₁Se₁

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表 1 计算得到的单胞晶格数据

Table 1. Calculated crystal lattice datas of single cell

结构	a₀/nm	α/(°)	V/nm³	E_g/eV
菱方相GeTe	0.608 6	88.14	0.225 05	0.62
菱方相Ge₃₂Te₃₁Se₁	0.608 3	87.94	0.224 62	0.58
菱方相Ge₃₁Te₃₁Se₁	0.605 8	87.77	0.221 88	0.58
菱方相Ge₃₁Te₃₂	0.606 2	87.82	0.222 34	0.59
菱方相Ge₃₁Se₁Te₃₂	0.608 4	88.12	0.224 86	—
面心立方相GeTe	0.601 9	90	0.218 08	0.38
面心立方相Ge₃₂Te₃₁Se₁	0.600 3	90	0.216 34	0.40
面心立方相Ge₃₁Te₃₁Se₁	0.602 4	90	0.218 52	0.52
面心立方相Ge₃₁Te₃₂	0.599 4	90	0.215 37	0.31
面心立方相Ge₃₁Se₁Te₃₂	0.601 0	90	0.217 04	—
注：晶格常数a₀、晶胞角度α、惯用胞体积V以及带隙E_g。

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表 2 Se掺杂完美GeTe不同取代位置的形成能

Table 2. Formation energy of Se doping at different substitution positions in ideal GeTe eV

eV
Se掺杂	菱方相		面心立方相
Se掺杂	富Ge	富Te	富Ge	富Te
取代Ge	1.05	0.88	0.67	0.50
取代Te	-0.41	-0.24	-0.54	-0.37

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