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
IdentifiersURN: urn:nbn:se:liu:diva-13578DOI: 10.1116/1.1636157OAI: oai:DiVA.org:liu-13578DiVA: diva2:20982