Thin films of PtAl2 and AuAl2 by solid-state reactive synthesis

The intermetallic compounds AuAl2 and PtAl2 are colored purple and yellow respectively. In the past they have been prepared by bulk melting techniques or by co-deposition in a magnetron sputterer. Here, however, we investigate films of AuAl2, PtAl2 and (Au,Pt)Al2 prepared by sequential physical vapo...

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Bibliographic Details
Published in:Thin solid films 2015-08, Vol.589, p.805-812
Main Authors: Supansomboon, S., Dowd, A., Gentle, A., van der Lingen, E., Cortie, M.B.
Format: Article
Language:English
Subjects:
Color
Decomposition
Deposition
Dielectric properties
Diffraction
Intermetallics
Melting
Microstructure
Thin films
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Summary:The intermetallic compounds AuAl2 and PtAl2 are colored purple and yellow respectively. In the past they have been prepared by bulk melting techniques or by co-deposition in a magnetron sputterer. Here, however, we investigate films of AuAl2, PtAl2 and (Au,Pt)Al2 prepared by sequential physical vapor deposition of the elements, followed by in situ solid-state reaction. The microstructure, dielectric functions, optical properties and thermal stability of the resulting films are characterized and compared to those prepared by bulk melting or co-deposition. The (Au,Pt)Al2 films show a color gamut that stretches from purple to brassy yellow depending on composition and microstructure. High temperature synchrotron X-ray diffraction experiments show that the (Au,Pt)Al2 phase is metastable, decomposing when heated above 420 degree C. In contrast, the pure AuAl2 or PtAl2 phases are stable to about 580 degree C before they oxidize or decompose. The alternative possibility of producing the purple-to-yellow color gamut by depositing optical stacks of very thin films of AuAl2 and PtAl2 is also assessed. Either scheme will provide a range of colors lying between those of the binary compound endpoints. Calculations predict that deposition of AuAl2 onto PtAl2 will produce more intense colors than vice versa, an unexpected finding that is worth further investigation.
ISSN:0040-6090
DOI:10.1016/j.tsf.2015.07.019