Journal ArticleDOI
Microstructure of α-alumina thin films deposited at low temperatures on chromia template layers
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In this paper, radio frequency sputtering has been used to deposit α-alumina (α-Al2O3) thin films at substrate temperatures of 280-560°C.Abstract:
Radio frequency sputtering has been used to deposit α-alumina (α-Al2O3) thin films at substrate temperatures of 280–560 °C. The films are shown to be single phased and hard. Nanoindentation gives values of 306±31 and 27±3 GPa for elastic modulus and hardness, respectively, for a substrate temperature of 280 °C. Growth of the α phase was achieved by in situ predeposition of a chromia template layer. Chromia crystallizes in the same hexagonal structure as α-alumina, with a lattice mismatch of 4.1% in the a- and 4.6% in the c-parameter, and is shown to nucleate readily on the amorphous substrates (silicon with a natural oxide layer). This results in local epitaxy of α-alumina on the chromia layer, as is shown by transmission electron microscopy. The alumina grains are columnar with grain widths increasing from 22±7 to 41±9 nm, as the temperature increases from 280 to 560 °C. This is consistent with a surface diffusion dominated growth mode and suggests that α-alumina deposition at low temperatures is possibl...read more
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Pulse enhanced electron emission (P3e™) arc evaporation and the synthesis of wear resistant Al–Cr–O coatings in corundum structure
TL;DR: P3e (TM) is a new approach in PVD technology for the deposition of metal oxides as mentioned in this paper, which is dedicated to the formation of alumina-based and other metallic oxide layers and comprises high current pulse technique for arc sources.
Journal ArticleDOI
Thermal stability of alumina thin films containing γ-Al2O3 phase prepared by reactive magnetron sputtering
TL;DR: In this paper, the thermal stability of alumina thin films containing γ-Al2O3 phase and its conversion to a thermodynamically stable α-Al 2O 3 phase during a post-deposition equilibrium thermal annealing was reported.
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Structure and surface energy of low-index surfaces of stoichiometric α-Al2O3 and α-Cr2O3
TL;DR: In this paper, the Hartree-Fock analysis of the surface energy of α-alumina and α-chromia has been used as a template for α-Al2O3 growth.
Journal ArticleDOI
Synthesis of α-Al2O3 thin films using reactive high-power impulse magnetron sputtering
TL;DR: In this article, α-alumina coatings have been deposited directly onto cemented-carbide and Mo substrates at a temperature as low as 650 °C using reactive high-power impulse magnetron sputtering (HiPIMS) of Al in an...
Journal ArticleDOI
Phase control of Al2O3 thin films grown at low temperatures
TL;DR: In this paper, a low-temperature growth of α-Al2O3 thin films by reactive magnetron sputtering was achieved for the first time, and the films were grown onto Cr2O 3 nucleation layers and the effects of the tota...
References
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Journal ArticleDOI
An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments
Warren C. Oliver,George M. Pharr +1 more
TL;DR: In this paper, the authors used a Berkovich indenter to determine hardness and elastic modulus from indentation load-displacement data, and showed that the curve of the curve is not linear, even in the initial stages of the unloading process.
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Influence of apparatus geometry and deposition conditions on the structure and topography of thick sputtered coatings
TL;DR: Two cylindrically symmetric and complementary sputtering geometries, the post and hollow cathodes, were used to deposit thick coatings of various metals (Mo, Cr, Ti, Fe, Cu, and Al-alloy) onto glass and metallic substrates at deposition rates of 1000-2000 A/min under various conditions of substrate temperature, argon pressure, and plasma bombardment as mentioned in this paper.
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Metastable alumina polymorphs : Crystal structures and transition sequences
Igor Levin,David Brandon +1 more
TL;DR: The available literature on the crystal structure of the metastable alumina polymorphs and their associated transitions is critically reviewed and summarized in this article, where possible mechanisms for the phase transitions between the different alumina morphological polymorphs also discussed.
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Surface Energies and Thermodynamic Phase Stability in Nanocrystalline Aluminas
J. M. McHale,A. Auroux,A. Auroux,A. Auroux,A. J. Perrotta,A. J. Perrotta,A. J. Perrotta,Alexandra Navrotsky,Alexandra Navrotsky,Alexandra Navrotsky +9 more
TL;DR: In this article, it was shown that α-Al 2 O 3 is the thermodynamically stable phase of coarsely crystalline aluminum oxide and becomes thermodynamic stable at surface areas greater than 125 square meters per gram at 800 kelvin.
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Molecular dynamics simulations of α-alumina and γ-alumina surfaces
TL;DR: In this paper, molecular dynamics simulations of crystalline aluminum oxide were performed for α-Al2O3 and γ-Al 2O3 phases, both bulk crystals and surfaces of each phase were studied.