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Title: First-principles study of twin grain boundaries in epitaxial BaSi{sub 2} on Si(111)

Abstract

Epitaxial films of BaSi{sub 2} on Si(111) for solar cell applications possess three epitaxial variants and exhibit a minority carrier diffusion length (ca. 9.4 μm) much larger than the domain size (ca. 0.2 μm); thus, the domain boundaries (DBs) between the variants do not act as carrier recombination centers. In this work, transmission electron microscopy (TEM) was used to observe the atomic arrangements around the DBs in BaSi{sub 2} epitaxial films on Si(111), and the most stable atomic configuration was determined by first-principles calculations based on density functional theory to provide possible interface models. Bright-field TEM along the a-axis of BaSi{sub 2} revealed that each DB was a twin boundary between two different epitaxial variants, and that Ba{sup (II)} atoms form hexagons containing central Ba{sup (I)} atoms in both the bulk and DB regions. Four possible interface models containing Ba{sup (I)}-atom interface layers were constructed, each consistent with TEM observations and distinguished by the relationship between the Si tetrahedron arrays in the two domains adjacent across the interface. This study assessed the structural relaxation of initial interface models constructed from surface slabs terminated by Ba{sup (I)} atoms or from zigzag surface slabs terminated by Si tetrahedra and Ba{sup (II)} atoms. In thesemore » models, the interactions or relative positions between Si tetrahedra appear to dominate the relaxation behavior and DB energies. One of the four interface models whose relationship between first-neighboring Si tetrahedra across the interface was the same as that in the bulk was particularly stable, with a DB energy of 95 mJ/m{sup 2}. There were no significant differences in the partial densities of states and band gaps between the bulk and DB regions, and it was therefore concluded that such DBs do not affect the minority carrier properties of BaSi{sub 2}.« less

Authors:
;  [1];  [2]
  1. Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan)
  2. Research Institute of Electrochemical Energy, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology, Ikeda, Osaka 563-8577 (Japan)
Publication Date:
OSTI Identifier:
22598845
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMS; BARIUM COMPOUNDS; DENSITY FUNCTIONAL METHOD; DENSITY OF STATES; DIFFUSION LENGTH; EPITAXY; FILMS; GRAIN BOUNDARIES; INTERFACES; RECOMBINATION; RELAXATION; SILICON SOLAR CELLS; SLABS; SURFACES; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Baba, Masakazu, Suemasu, Takashi, E-mail: suemasu@bk.tsukuba.ac.jp, and Kohyama, Masanori. First-principles study of twin grain boundaries in epitaxial BaSi{sub 2} on Si(111). United States: N. p., 2016. Web. doi:10.1063/1.4961603.
Baba, Masakazu, Suemasu, Takashi, E-mail: suemasu@bk.tsukuba.ac.jp, & Kohyama, Masanori. First-principles study of twin grain boundaries in epitaxial BaSi{sub 2} on Si(111). United States. doi:10.1063/1.4961603.
Baba, Masakazu, Suemasu, Takashi, E-mail: suemasu@bk.tsukuba.ac.jp, and Kohyama, Masanori. Sun . "First-principles study of twin grain boundaries in epitaxial BaSi{sub 2} on Si(111)". United States. doi:10.1063/1.4961603.
@article{osti_22598845,
title = {First-principles study of twin grain boundaries in epitaxial BaSi{sub 2} on Si(111)},
author = {Baba, Masakazu and Suemasu, Takashi, E-mail: suemasu@bk.tsukuba.ac.jp and Kohyama, Masanori},
abstractNote = {Epitaxial films of BaSi{sub 2} on Si(111) for solar cell applications possess three epitaxial variants and exhibit a minority carrier diffusion length (ca. 9.4 μm) much larger than the domain size (ca. 0.2 μm); thus, the domain boundaries (DBs) between the variants do not act as carrier recombination centers. In this work, transmission electron microscopy (TEM) was used to observe the atomic arrangements around the DBs in BaSi{sub 2} epitaxial films on Si(111), and the most stable atomic configuration was determined by first-principles calculations based on density functional theory to provide possible interface models. Bright-field TEM along the a-axis of BaSi{sub 2} revealed that each DB was a twin boundary between two different epitaxial variants, and that Ba{sup (II)} atoms form hexagons containing central Ba{sup (I)} atoms in both the bulk and DB regions. Four possible interface models containing Ba{sup (I)}-atom interface layers were constructed, each consistent with TEM observations and distinguished by the relationship between the Si tetrahedron arrays in the two domains adjacent across the interface. This study assessed the structural relaxation of initial interface models constructed from surface slabs terminated by Ba{sup (I)} atoms or from zigzag surface slabs terminated by Si tetrahedra and Ba{sup (II)} atoms. In these models, the interactions or relative positions between Si tetrahedra appear to dominate the relaxation behavior and DB energies. One of the four interface models whose relationship between first-neighboring Si tetrahedra across the interface was the same as that in the bulk was particularly stable, with a DB energy of 95 mJ/m{sup 2}. There were no significant differences in the partial densities of states and band gaps between the bulk and DB regions, and it was therefore concluded that such DBs do not affect the minority carrier properties of BaSi{sub 2}.},
doi = {10.1063/1.4961603},
journal = {Journal of Applied Physics},
number = 8,
volume = 120,
place = {United States},
year = {Sun Aug 28 00:00:00 EDT 2016},
month = {Sun Aug 28 00:00:00 EDT 2016}
}