Thin films of PtAl<inf>2</inf> and AuAl<inf>2</inf> by solid-state reactive synthesis
- Publication Type:
- Journal Article
- Thin Solid Films, 2015, 589 pp. 805 - 812
- Issue Date:
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© 2015 Elsevier B.V. The intermetallic compounds AuAl
2 and PtAl 2 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 AuAl 2, PtAl 2 and (Au,Pt)Al 2 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)Al 2 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)Al 2 phase is metastable, decomposing when heated above 420 °C. In contrast, the pure AuAl 2 or PtAl 2 phases are stable to about 580 °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 AuAl 2 and PtAl 2 is also assessed. Either scheme will provide a range of colors lying between those of the binary compound endpoints. Calculations predict that deposition of AuAl 2 onto PtAl 2 will produce more intense colors than vice versa, an unexpected finding that is worth further investigation.
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