Atomic structure of amorphous and crystallized Ge{sub 15}Sb{sub 85}

Journal Article · Sat May 15 00:00:00 EDT 2010 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3380667· OSTI ID:21476269

Zalden, Peter; Eijk, Julia van; Wuttig, Matthias ^[1]; Bichara, Christophe ^[2]; Braun, Carolin; Bensch, Wolfgang ^[3]

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1. I. Physikalisches Institut (IA), RWTH Aachen, 52056 Aachen (Germany)
2. CiNaM-Centre Interdisciplinaire de Nanoscience de Marseille, Campus de Luminy, 13288 Marseille (France)
3. Institut fuer Anorganische Chemie, Universitaet Kiel, Max-Eyth Str. 2, 24118 Kiel (Germany)

Ge{sub 15}Sb{sub 85} is a promising material for phase-change memory applications owing to its very short crystallization times. As deposited amorphous samples of sputter deposited Ge{sub 15}Sb{sub 85} have been investigated by extended x-ray absorption fine structure (EXAFS) measurements on both, Sb and Ge K absorption edges. After crystallizing the specimen, x-ray diffraction (XRD) and EXAFS measurements have been performed to analyze the atomic structure at different annealing conditions. Thus, experimental techniques focusing on the long range order as well as on the local order have been combined. Sb atoms have on average 3.2(2) nearest neighbors, while Ge atoms have 4.0(3). The Ge-Ge and Ge-Sb bond lengths are determined to 2.46(2) and 2.66(1) A, respectively and agree well with those observed in the amorphous phase of the common phase-change material Ge{sub 2}Sb{sub 2}Te{sub 5}. After crystallizing the sample at 250 deg. C, very different EXAFS spectra with modified Ge-Sb bond lengths are observed. The higher concentration of Ge neighbors at the Ge edge as compared to the as-deposited sample is indicative for phase separation. For the corresponding sample, XRD does not show reflections of Ge, which indicates that the agglomeration of Ge is amorphous or below the coherence length of the x-radiation. The EXAFS spectrum shows a superposition of two phases: one with bond lengths which agree with sp{sup 3}-hybridized Ge [2.43(1) A] and another one with longer Ge-Ge bond lengths [2.79(8) A]. This result can be explained by phase separation in the material.

• OSTI ID: 21476269
• Journal Information: Journal of Applied Physics, Vol. 107, Issue 10; Other Information: DOI: 10.1063/1.3380667; (c) 2010 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
AGGLOMERATION
AMORPHOUS STATE
ANNEALING
ANTIMONY ALLOYS
BOND LENGTHS
COHERENCE LENGTH
CRYSTALLIZATION
ELECTRONIC STRUCTURE
FINE STRUCTURE
GERMANIUM ALLOYS
K ABSORPTION
PHASE CHANGE MATERIALS
SPUTTERING
SURFACE COATING
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY
ABSORPTION
ALLOYS
COHERENT SCATTERING
DEPOSITION
DIFFRACTION
DIMENSIONS
HEAT TREATMENTS
LENGTH
MATERIALS
PHASE TRANSFORMATIONS
SCATTERING
SORPTION
SPECTROSCOPY