Thermal stability of simple tetragonal and hexagonal diamond germanium

L. Q. Huston; B. C. Johnson; B. Haberl; S. Wong; J. S. Williams; J. E. Bradby

doi:10.1063/1.5002705

Thermal stability of simple tetragonal and hexagonal diamond germanium

L. Q. Huston, B. C. Johnson, B. Haberl, S. Wong, J. S. Williams, J. E. Bradby

High Pressure

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Abstract

Exotic phases of germanium, that form under high pressure but persist under ambient conditions, are of technological interest due to their unique optical and electrical properties. The thermal evolution and stability of two of these exotic Ge phases, the simple tetragonal (st12) and hexagonal diamond (hd) phases, are investigated in detail. These metastable phases, formed by high pressure decompression in either a diamond anvil cell or by nanoindentation, are annealed at temperatures ranging from 280 to 320 °C for st12-Ge and 200 to 550 °C for hd-Ge. In both cases, the exotic phases originated from entirely pure Ge precursor materials. Raman microspectroscopy is used to monitor the phase changes ex situ following annealing. Our results show that hd-Ge synthesized via a pure form of a-Ge first undergoes a subtle change in structure and then an irreversible phase transformation to dc-Ge with an activation energy of (4.3 ± 0.2) eV at higher temperatures. St12-Ge was found to transform to dc-Ge with an activation energy of (1.44 ± 0.08) eV. Taken together with results from previous studies, this study allows for intriguing comparisons with silicon and suggests promising technological applications.

Original language	English
Article number	175108
Journal	Journal of Applied Physics
Volume	122
Issue number	17
DOIs	https://doi.org/10.1063/1.5002705
State	Published - Nov 7 2017

Funding

The authors would like to thank AFAiiR (NCRIS), the Centre for Advanced Microscopy (CAM), and the Australian National Fabrication Facility (ANFF) for use of their facilities and technical support. This work was supported by the Australian Research Council under the Discovery Project Scheme. L.Q.H. is supported by an Australian Government Research Training Program Scholarship. J.E.B. acknowledges the ARC for the award of a Future Fellowship. B.H. was supported through a Weinberg Fellowship (ORNL) and the Neutron Scattering User Facilities (ORNL), supported by the U.S. Department of Energy, Office of Sciences, Basic Energy Sciences. The ORNL is funded under DOE-BES Contract No. DE-AC05-00OR22725 and the Alvin M. Weinberg Fellowship by the ORNL LDRD scheme under Project No. 7620.

Funders	Funder number
DOE-BES	DE-AC05-00OR22725
ORNL LDRD	7620
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Oak Ridge National Laboratory
Australian Research Council

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abstract = "Exotic phases of germanium, that form under high pressure but persist under ambient conditions, are of technological interest due to their unique optical and electrical properties. The thermal evolution and stability of two of these exotic Ge phases, the simple tetragonal (st12) and hexagonal diamond (hd) phases, are investigated in detail. These metastable phases, formed by high pressure decompression in either a diamond anvil cell or by nanoindentation, are annealed at temperatures ranging from 280 to 320 °C for st12-Ge and 200 to 550 °C for hd-Ge. In both cases, the exotic phases originated from entirely pure Ge precursor materials. Raman microspectroscopy is used to monitor the phase changes ex situ following annealing. Our results show that hd-Ge synthesized via a pure form of a-Ge first undergoes a subtle change in structure and then an irreversible phase transformation to dc-Ge with an activation energy of (4.3 ± 0.2) eV at higher temperatures. St12-Ge was found to transform to dc-Ge with an activation energy of (1.44 ± 0.08) eV. Taken together with results from previous studies, this study allows for intriguing comparisons with silicon and suggests promising technological applications.",

author = "Huston, {L. Q.} and Johnson, {B. C.} and B. Haberl and S. Wong and Williams, {J. S.} and Bradby, {J. E.}",

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AU - Johnson, B. C.

AU - Haberl, B.

AU - Wong, S.

AU - Williams, J. S.

AU - Bradby, J. E.

PY - 2017/11/7

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N2 - Exotic phases of germanium, that form under high pressure but persist under ambient conditions, are of technological interest due to their unique optical and electrical properties. The thermal evolution and stability of two of these exotic Ge phases, the simple tetragonal (st12) and hexagonal diamond (hd) phases, are investigated in detail. These metastable phases, formed by high pressure decompression in either a diamond anvil cell or by nanoindentation, are annealed at temperatures ranging from 280 to 320 °C for st12-Ge and 200 to 550 °C for hd-Ge. In both cases, the exotic phases originated from entirely pure Ge precursor materials. Raman microspectroscopy is used to monitor the phase changes ex situ following annealing. Our results show that hd-Ge synthesized via a pure form of a-Ge first undergoes a subtle change in structure and then an irreversible phase transformation to dc-Ge with an activation energy of (4.3 ± 0.2) eV at higher temperatures. St12-Ge was found to transform to dc-Ge with an activation energy of (1.44 ± 0.08) eV. Taken together with results from previous studies, this study allows for intriguing comparisons with silicon and suggests promising technological applications.

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Thermal stability of simple tetragonal and hexagonal diamond germanium

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