Plasmon resonance in a TiO2-Au NPs structures

Investigated structures were deposited on a pre cleaned Corning 1737 glass substrates, which provided flat optical transmission characteristics and high transmission coefficient in a visible light range. Plasmonic nanostructures were formed as a result of thermal annealing. For gold films with thickness of 2.8 nm depiction a table-top dc magnetron sputtering system (EM SCD 500, Leica), equipped with quartz microbalance for in-situ thickness measurements, was used. Films were deposited from a high purity (99.99%) gold target in pure argon (99.999%) plasma. For film deposition with a rate of ca. 0.1nm/s, ca. 10W of incident power was applied. Annealing of gold thin film, for 15 min at 550 °C in air atmosphere, resulted in forming spherical isolated islands. TiO2 thin film, with thickness of 200 nm, was prepared by radio frequency (RF) magnetron sputtering process, using Omicron NanoScience, four targets sputter system. Ti target was sputtered in an argon-oxygen atmosphere (Ar:O2 flow ratio: 5sccm:30sccm, both gasses with purity of 99.999%). Used of RF power of 60W resulted in deposition with a ratio ca. 0.05 nm/s. Substrates with plasmonic nanostructures were heated to 200 ⁰C during TiO2 film deposition process. Optical properties of manufactured structures were investigated using Evolution 220 UV-Visible Spectrophotometer in a range of 200 nm – 1000 nm. Measured optical properties of structures with various thickness of initial Au layer (1.5, 2.8 and 4.0 nm) and various profiles of heating, during manufacturing.