Abstract
We report on allotropic phase transformation and nanograin refinement of Ge by severe plastic deformation using high-pressure torsion (HPT) under a pressure of 24 GPa. No appreciable formation of metastable phases occurred under compression prior to torsion, while a diamond cubic Ge-I phase and a tetragonal Ge-III phase were observed in the HPT-processed samples. The formation of the Ge-III phase was enhanced by introduction of shear strain. TEM observations revealed that HPT-processed samples consisted of micro- and nanograins. It was indicated that grain refinement occurred due to the introduction of high density of lattice defects in metallic Ge-II during HPT processing, and then Ge-II transformed not only back to Ge-I but also to metastable Ge-III upon unloading. The Ge-III phase reversely transformed to Ge-I by intense Ar-ion laser irradiation or by thermal annealing. No appreciable photoluminescence (PL) was observed from the HPT-processed sample, while a broad PL peak in the range of 600–800 nm appeared after intense laser irradiation. A similar PL peak was also observed from thermally annealed samples. These results suggest that the appearance of the PL peak arises from Ge-I nanograins.
| Original language | English |
|---|---|
| Pages (from-to) | 138-143 |
| Number of pages | 6 |
| Journal | Journal of Materials Science |
| Volume | 51 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - Aug 11 2015 |
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All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering
Cite this
Allotropic phase transformation and photoluminescence of germanium nanograins processed by high-pressure torsion. / Ikoma, Yoshifumi; Toyota, Takamitsu; Ejiri, Yoshimasa; Saito, Katsuhiko; Guo, Qixin; Horita, Zenji.
In: Journal of Materials Science, Vol. 51, No. 1, 11.08.2015, p. 138-143.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Allotropic phase transformation and photoluminescence of germanium nanograins processed by high-pressure torsion
AU - Ikoma, Yoshifumi
AU - Toyota, Takamitsu
AU - Ejiri, Yoshimasa
AU - Saito, Katsuhiko
AU - Guo, Qixin
AU - Horita, Zenji
PY - 2015/8/11
Y1 - 2015/8/11
N2 - We report on allotropic phase transformation and nanograin refinement of Ge by severe plastic deformation using high-pressure torsion (HPT) under a pressure of 24 GPa. No appreciable formation of metastable phases occurred under compression prior to torsion, while a diamond cubic Ge-I phase and a tetragonal Ge-III phase were observed in the HPT-processed samples. The formation of the Ge-III phase was enhanced by introduction of shear strain. TEM observations revealed that HPT-processed samples consisted of micro- and nanograins. It was indicated that grain refinement occurred due to the introduction of high density of lattice defects in metallic Ge-II during HPT processing, and then Ge-II transformed not only back to Ge-I but also to metastable Ge-III upon unloading. The Ge-III phase reversely transformed to Ge-I by intense Ar-ion laser irradiation or by thermal annealing. No appreciable photoluminescence (PL) was observed from the HPT-processed sample, while a broad PL peak in the range of 600–800 nm appeared after intense laser irradiation. A similar PL peak was also observed from thermally annealed samples. These results suggest that the appearance of the PL peak arises from Ge-I nanograins.
AB - We report on allotropic phase transformation and nanograin refinement of Ge by severe plastic deformation using high-pressure torsion (HPT) under a pressure of 24 GPa. No appreciable formation of metastable phases occurred under compression prior to torsion, while a diamond cubic Ge-I phase and a tetragonal Ge-III phase were observed in the HPT-processed samples. The formation of the Ge-III phase was enhanced by introduction of shear strain. TEM observations revealed that HPT-processed samples consisted of micro- and nanograins. It was indicated that grain refinement occurred due to the introduction of high density of lattice defects in metallic Ge-II during HPT processing, and then Ge-II transformed not only back to Ge-I but also to metastable Ge-III upon unloading. The Ge-III phase reversely transformed to Ge-I by intense Ar-ion laser irradiation or by thermal annealing. No appreciable photoluminescence (PL) was observed from the HPT-processed sample, while a broad PL peak in the range of 600–800 nm appeared after intense laser irradiation. A similar PL peak was also observed from thermally annealed samples. These results suggest that the appearance of the PL peak arises from Ge-I nanograins.
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U2 - 10.1007/s10853-015-9328-y
DO - 10.1007/s10853-015-9328-y
M3 - Article
VL - 51
SP - 138
EP - 143
JO - Journal of Materials Science
JF - Journal of Materials Science
SN - 0022-2461
IS - 1
ER -