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Title: Effect of Si additions on thermal stability and the phase transition sequence of sputtered amorphous alumina thin films

Si-alloyed amorphous alumina coatings having a silicon concentration of 0 to 2.7 at. % were deposited by combinatorial reactive pulsed DC magnetron sputtering of Al and Al-Si (90-10 at. %) split segments in Ar/O{sub 2} atmosphere. The effect of Si alloying on thermal stability of the as-deposited amorphous alumina thin films and the phase formation sequence was evaluated by using differential scanning calorimetry and X-ray diffraction. The thermal stability window of the amorphous phase containing 2.7 at. % of Si was increased by more than 100 °C compared to that of the unalloyed phase. A similar retarding effect of Si alloying was also observed for the α-Al{sub 2}O{sub 3} formation temperature, which increased by more than 120 °C. While for the latter retardation, the evidence for the presence of SiO{sub 2} at the grain boundaries was presented previously, this obviously cannot explain the stability enhancement reported here for the amorphous phase. Based on density functional theory molecular dynamics simulations and synchrotron X-ray diffraction experiments for amorphous Al{sub 2}O{sub 3} with and without Si incorporation, we suggest that the experimentally identified enhanced thermal stability of amorphous alumina with addition of Si is due to the formation of shorter and stronger Si–O bonds as compared to Al–Omore » bonds.« less
Authors:
; ; ; ; ; ; ;  [1] ; ;  [2]
  1. Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen (Germany)
  2. Deutsches Elektronen Synchrotron DESY, FS-PE group, Notkestrasse 85, D-22607 Hamburg (Germany)
Publication Date:
OSTI Identifier:
22412844
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM OXIDES; AMORPHOUS STATE; CALORIMETRY; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CONCENTRATION RATIO; DENSITY FUNCTIONAL METHOD; GRAIN BOUNDARIES; MOLECULAR DYNAMICS METHOD; PHASE TRANSFORMATIONS; SILICON; SILICON ALLOYS; SILICON OXIDES; SPUTTERING; THIN FILMS; X-RAY DIFFRACTION