Effect of twins on crystal growth of polycrystalline silicon for solar cells

Hirofumi Miyahara, Seiko Nara, Masayuki Okugawa, Keisaku Ogi

Research output: Contribution to journalArticle

Abstract

The microstructure of polycrystalline silicon has been investigated through a unidirectional solidification technique, and the mechanism of the twin growth on a reentrant corner has been evaluated. A columnar structure is observed in the rod-like silicone specimens, which are solidified at a velocity from 1.25 to 40 μm/s in an electric resistance furnace with a positive temperature gradient of 20 K/cm. At slow velocity from 1.25 to 2.5 μm/s, the grain sizes increase as solidification proceeds. However, mean grain sizes decrease with increasing solidification velocity, and at the central part of specimens the equiaxed grains appear above a critical velocity of around 40 μm/s. Most of the columnar grains have twin boundaries in them, and grains with several twins grow larger than twin-free grains. To increase grain size, it is necessary to keep the solidification velocity low and to introduce the twins. The supercooling of directional growth is less than 4 K at a velocity from 2.5 to 30 μm/s. A model of two-dimensional nucleation on the reentrant corner has been established and their critical nucleation radii are calculated from 70% to 80% of the radii of those of general two-dimensional nucleation. The decrease of the critical radius on the reentrant corner would reduce the supercooling of grain growth. Therefore, the grains with twins could preferentially grow and enlarge in a competitive growth.

Original languageEnglish
Pages (from-to)919-926
Number of pages8
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Volume68
Issue number10
DOIs
Publication statusPublished - Oct 2004

Fingerprint

Crystallization
Crystal growth
Polysilicon
crystal growth
Solar cells
solar cells
solidification
Solidification
silicon
Supercooling
Nucleation
grain size
nucleation
supercooling
radii
critical velocity
silicones
Silicones
Grain growth
Thermal gradients

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry

Cite this

Effect of twins on crystal growth of polycrystalline silicon for solar cells. / Miyahara, Hirofumi; Nara, Seiko; Okugawa, Masayuki; Ogi, Keisaku.

In: Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals, Vol. 68, No. 10, 10.2004, p. 919-926.

Research output: Contribution to journalArticle

@article{2fa53c4bec8c4df7a6761aab398d757a,
title = "Effect of twins on crystal growth of polycrystalline silicon for solar cells",
abstract = "The microstructure of polycrystalline silicon has been investigated through a unidirectional solidification technique, and the mechanism of the twin growth on a reentrant corner has been evaluated. A columnar structure is observed in the rod-like silicone specimens, which are solidified at a velocity from 1.25 to 40 μm/s in an electric resistance furnace with a positive temperature gradient of 20 K/cm. At slow velocity from 1.25 to 2.5 μm/s, the grain sizes increase as solidification proceeds. However, mean grain sizes decrease with increasing solidification velocity, and at the central part of specimens the equiaxed grains appear above a critical velocity of around 40 μm/s. Most of the columnar grains have twin boundaries in them, and grains with several twins grow larger than twin-free grains. To increase grain size, it is necessary to keep the solidification velocity low and to introduce the twins. The supercooling of directional growth is less than 4 K at a velocity from 2.5 to 30 μm/s. A model of two-dimensional nucleation on the reentrant corner has been established and their critical nucleation radii are calculated from 70{\%} to 80{\%} of the radii of those of general two-dimensional nucleation. The decrease of the critical radius on the reentrant corner would reduce the supercooling of grain growth. Therefore, the grains with twins could preferentially grow and enlarge in a competitive growth.",
author = "Hirofumi Miyahara and Seiko Nara and Masayuki Okugawa and Keisaku Ogi",
year = "2004",
month = "10",
doi = "10.2320/jinstmet.68.919",
language = "English",
volume = "68",
pages = "919--926",
journal = "Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals",
issn = "0021-4876",
publisher = "公益社団法人 日本金属学会",
number = "10",

}

TY - JOUR

T1 - Effect of twins on crystal growth of polycrystalline silicon for solar cells

AU - Miyahara, Hirofumi

AU - Nara, Seiko

AU - Okugawa, Masayuki

AU - Ogi, Keisaku

PY - 2004/10

Y1 - 2004/10

N2 - The microstructure of polycrystalline silicon has been investigated through a unidirectional solidification technique, and the mechanism of the twin growth on a reentrant corner has been evaluated. A columnar structure is observed in the rod-like silicone specimens, which are solidified at a velocity from 1.25 to 40 μm/s in an electric resistance furnace with a positive temperature gradient of 20 K/cm. At slow velocity from 1.25 to 2.5 μm/s, the grain sizes increase as solidification proceeds. However, mean grain sizes decrease with increasing solidification velocity, and at the central part of specimens the equiaxed grains appear above a critical velocity of around 40 μm/s. Most of the columnar grains have twin boundaries in them, and grains with several twins grow larger than twin-free grains. To increase grain size, it is necessary to keep the solidification velocity low and to introduce the twins. The supercooling of directional growth is less than 4 K at a velocity from 2.5 to 30 μm/s. A model of two-dimensional nucleation on the reentrant corner has been established and their critical nucleation radii are calculated from 70% to 80% of the radii of those of general two-dimensional nucleation. The decrease of the critical radius on the reentrant corner would reduce the supercooling of grain growth. Therefore, the grains with twins could preferentially grow and enlarge in a competitive growth.

AB - The microstructure of polycrystalline silicon has been investigated through a unidirectional solidification technique, and the mechanism of the twin growth on a reentrant corner has been evaluated. A columnar structure is observed in the rod-like silicone specimens, which are solidified at a velocity from 1.25 to 40 μm/s in an electric resistance furnace with a positive temperature gradient of 20 K/cm. At slow velocity from 1.25 to 2.5 μm/s, the grain sizes increase as solidification proceeds. However, mean grain sizes decrease with increasing solidification velocity, and at the central part of specimens the equiaxed grains appear above a critical velocity of around 40 μm/s. Most of the columnar grains have twin boundaries in them, and grains with several twins grow larger than twin-free grains. To increase grain size, it is necessary to keep the solidification velocity low and to introduce the twins. The supercooling of directional growth is less than 4 K at a velocity from 2.5 to 30 μm/s. A model of two-dimensional nucleation on the reentrant corner has been established and their critical nucleation radii are calculated from 70% to 80% of the radii of those of general two-dimensional nucleation. The decrease of the critical radius on the reentrant corner would reduce the supercooling of grain growth. Therefore, the grains with twins could preferentially grow and enlarge in a competitive growth.

UR - http://www.scopus.com/inward/record.url?scp=10444244299&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=10444244299&partnerID=8YFLogxK

U2 - 10.2320/jinstmet.68.919

DO - 10.2320/jinstmet.68.919

M3 - Article

AN - SCOPUS:10444244299

VL - 68

SP - 919

EP - 926

JO - Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals

JF - Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals

SN - 0021-4876

IS - 10

ER -