Optical properties of AlAu alloyed and intermetallic thin films

Noble metal alloys have been widely investigated as an alternative to pure metals for improving the optical response of optoelectronic devices operating in the visible range of the electromagnetic spectrum. However, their use is hardly extended to the ultra-violet (UV) range. As an alternative, aluminum-based alloys could expand the functionality of photonic devices into the UV range of the spectrum. In this work, we fabricated and measured the optical response of a binary mixture of gold (Au) and aluminum (Al) thin films. The thin films were deposited on a glass substrate via the co-sputtering method. The dielectric functions were measured using spectroscopic ellipsometry. Also, we investigated how the optical response of the thin films changed under a wide range of temperatures, from 25°C to 200°C. We demonstrate that, in some cases, a bimetallic material can outperform their pure metal counterparts after the temperature treatment, e.g., Al_0.15Au_0.85 shows an increased quality factor of its localized surface plasmon (Q_LSP) than pure Au and Al. Moreover, we observe that Al-rich thin films are stable, no significant changes were noticed in its dielectric function, as temperature increased.