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

    Research output: Contribution to journalArticlepeer-review

    12 Citations (Scopus)

    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 languageEnglish
    Article number175108
    JournalJournal of Applied Physics
    Volume122
    Issue number17
    DOIs
    Publication statusPublished - 7 Nov 2017

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