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.本研究制备的结构均沉积于经预清洁处理的康宁1737玻璃衬底（Corning 1737）之上，该衬底在可见光波段具备平坦的光学透射特性与较高的透射系数。等离子体纳米结构（plasmonic nanostructures）通过热退火工艺制备得到。针对厚度为2.8 nm的金薄膜，本研究采用台式直流磁控溅射系统（EM SCD 500，徕卡）进行沉积，该系统配备石英微天平以实现原位厚度监测。薄膜以纯度为99.99%的金靶材为原料，在纯度99.999%的氩等离子体环境中完成沉积。当沉积速率控制在约0.1 nm/s时，入射功率设置为约10 W。将金薄膜置于空气氛围中于550 ℃退火15 min，即可得到球形孤立岛状结构。厚度为200 nm的二氧化钛（TiO₂）薄膜通过射频（RF）磁控溅射工艺制备，所用设备为Omicron NanoScience公司的四靶溅射系统。溅射钛靶材的氛围为氩氧混合气体，流量比为Ar:O₂=5sccm:30sccm，两种气体的纯度均为99.999%。设置射频功率为60 W时，沉积速率约为0.05 nm/s。在二氧化钛薄膜沉积过程中，搭载等离子体纳米结构的衬底被加热至200 ℃。采用Evolution 220型紫外-可见分光光度计，在200 nm至1000 nm的波段范围内对所制备结构的光学性能进行了表征。本研究对初始金层厚度分别为1.5 nm、2.8 nm与4.0 nm，且制备过程中采用不同热制程曲线的结构的光学性能进行了测试。