Microstructure of α-alumina thin films deposited at low temperatures on chromia template layers
2004 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, Vol. 22, no 1, 117-121 p.Article in journal (Refereed) Published
Radio frequency sputtering has been used to deposit -alumina (-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 phase was achieved by in situ predeposition of a chromia template layer. Chromia crystallizes in the same hexagonal structure as -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 -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 -alumina deposition at low temperatures is possible once initial grain nucleation has occurred. Results are also presented demonstrating chromia/-alumina growth on a technological substrate (Haynes230 Ni-based super alloy, Haynes International, Inc.).
Place, publisher, year, edition, pages
2004. Vol. 22, no 1, 117-121 p.
alumina, chromium compounds, sputtered coatings, indentation, elastic moduli, hardness, sputter deposition, transmission electron microscopy, epitaxial layers, grain size, surface diffusion, nucleation, wear resistant coatings, thermal barrier coatings
National CategoryNatural Sciences
IdentifiersURN: urn:nbn:se:liu:diva-13578DOI: 10.1116/1.1636157OAI: oai:DiVA.org:liu-13578DiVA: diva2:20982