Temperature stability of thin film refractory plasmonic materials

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Gold (Au) and silver (Ag) are standard plasmonic materials but lack high-temperature stability.
• Refractory materials offer potential for robust plasmonic applications at elevated temperatures.
• Reproducibility of optical properties after thermal cycling is crucial but understudied.

Purpose of the Study:

• To assess the viability of W, Mo, Ti, TiN, TiON, Ag, Au, SrRuO3, and SrNbO3 for refractory plasmonic applications.
• To investigate the impact of thermal cycling on the optical properties and metallic behavior of these materials.
• To compare their performance against established plasmonic materials like Au and Ag.

Main Methods:

• Thin films (50-105 nm) were deposited on MgO, SrTiO3, and Si substrates using e-beam evaporation, RF magnetron sputtering, and pulsed laser deposition.
• Characterization included Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), spectroscopic ellipsometry, and DC resistivity.
• Samples were annealed in air at temperatures from 300°C to 1000°C for one hour to determine maximum cycling temperatures and longevity.

Main Results:

• SrRuO3 maintained metallic behavior up to 800°C.
• SrNbO3 lost metallic behavior after annealing at 400°C due to a phase transition.
• TiN and TiON degraded due to oxidation, losing metallic behavior at 500°C, while Au degraded at 600°C.

Conclusions:

• TiN and TiON exhibit better high-temperature stability than Au and SrRuO3 under certain conditions.
• TiN and TiON are potentially superior to Au or SRO for high-temperature applications in vacuum.
• Further research is needed to fully understand the long-term durability and specific application niches for these refractory plasmonic materials.