High-resolution transmission electron microscopy analysis of nanograined germanium produced by high-pressure torsion

Yoshifumi Ikoma, Kazuki Kumano, Kaveh Edalati, Martha McCartney, David Smith, Zenji Horita

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The nanostructure of bulk nanograined germanium (Ge) processed by high-pressure torsion (HPT) has been analyzed by high-resolution electron microscopy. Crystalline Ge disks were subjected to HPT under the nominal pressure of 24 GPa. The samples processed at room temperature consisted of diamond-cubic Ge-I and simple-tetragonal Ge-III nanograins in addition to amorphous regions. The samples contained lattice defects such as dislocations, nanotwins, and stacking faults. Subsequent annealing at 573 K led to the phase transformation from Ge-III to Ge-I, but residual Ge-III nanograins and lattice defects remained due to the low annealing temperature. It was found that Ge-I as well as residual Ge-III nanograins and some amorphous phase were present after processing by HPT at cryogenic temperature. No other metastable phases such as body-centered-cubic Ge-IV or hexagonal-diamond Ge-V were observed in the cryogenic HPT-processed sample.

Original languageEnglish (US)
Pages (from-to)132-138
Number of pages7
JournalMaterials Characterization
Volume132
DOIs
StatePublished - Oct 1 2017

Fingerprint

Germanium
High resolution transmission electron microscopy
Torsional stress
torsion
germanium
transmission electron microscopy
high resolution
Diamond
Crystal defects
Cryogenics
Diamonds
diamonds
Annealing
annealing
Metastable phases
High resolution electron microscopy
defects
Stacking faults
cryogenic temperature
Dislocations (crystals)

Keywords

  • High-pressure torsion
  • HRTEM
  • Lattice defects
  • Metastable phase
  • Phase transformation

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

High-resolution transmission electron microscopy analysis of nanograined germanium produced by high-pressure torsion. / Ikoma, Yoshifumi; Kumano, Kazuki; Edalati, Kaveh; McCartney, Martha; Smith, David; Horita, Zenji.

In: Materials Characterization, Vol. 132, 01.10.2017, p. 132-138.

Research output: Contribution to journalArticle

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AU - Smith, David

AU - Horita, Zenji

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AB - The nanostructure of bulk nanograined germanium (Ge) processed by high-pressure torsion (HPT) has been analyzed by high-resolution electron microscopy. Crystalline Ge disks were subjected to HPT under the nominal pressure of 24 GPa. The samples processed at room temperature consisted of diamond-cubic Ge-I and simple-tetragonal Ge-III nanograins in addition to amorphous regions. The samples contained lattice defects such as dislocations, nanotwins, and stacking faults. Subsequent annealing at 573 K led to the phase transformation from Ge-III to Ge-I, but residual Ge-III nanograins and lattice defects remained due to the low annealing temperature. It was found that Ge-I as well as residual Ge-III nanograins and some amorphous phase were present after processing by HPT at cryogenic temperature. No other metastable phases such as body-centered-cubic Ge-IV or hexagonal-diamond Ge-V were observed in the cryogenic HPT-processed sample.

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