Pressure-induced transformations in amorphous Si-Ge alloy

Journal Article · Wed Mar 14 00:00:00 EDT 2012 · Phys. Rev. B

DOI:https://doi.org/10.1103/PhysRevB.85.045201· OSTI ID:1033004

Coppari, F; Polian, A; Menguy, N; Trapananti, A; Congeduti, A; Newville, M; Prakapenka, V B; Choi, Y; Principi, E; Di Cicco, A ^[1]

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1. CNRS-UMR

The pressure behavior of an amorphous Si-rich SiGe alloy ({alpha}-Si{sub x}Ge{sub 1-x}, x = 0.75) has been investigated up to about 30 GPa, by a combination of Raman spectroscopy, x-ray absorption spectroscopy, and x-ray diffraction measurements. The trends of microscopic structural properties and of the Raman-active phonon modes are presented in the whole pressure range. Nucleation of nanocrystalline alloy particles and metallization have been observed above 12 GPa, with a range of about 2 GPa of coexistence of amorphous and crystalline phases. Transformations from the amorphous tetrahedral, to the crystalline tetragonal ({beta}-Sn) and to the simple hexagonal structures have been observed around 13.8 and 21.8 GPa. The recovered sample upon depressurization, below about 4 GPa, shows a local structure similar to the as-deposited one. Inhomogeneities of the amorphous texture at the nanometric scale, probed by high-resolution transmission electron microscopy, indicate that the recovered amorphous sample has a different ordering at this scale, and therefore the transformations can not be considered fully reversible. The role of disordered grain boundaries at high pressure and the possible presence of a high-density amorphous phase are discussed.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: FOREIGNNSFDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1033004
• Journal Information: Phys. Rev. B, Vol. 85, Issue (4) ; 01, 2012; ISSN 1098-0121
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
AMORPHOUS STATE
GERMANIUM ALLOYS
DEPRESSURIZATION
GRAIN BOUNDARIES
NUCLEATION
PHONONS
PRESSURE RANGE GIGA PA
RAMAN SPECTROSCOPY
SILICON ALLOYS
TEXTURE
TRANSFORMATIONS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY