Effect of annealing treatment on characteristics of surface plasmon resonance for indium tin oxide

Abstract

With the development of modern micro-processing technology, the basic theory and relevant applications for surface plasmon have formed a new research direction which is known as surface plasmon photonics. The traditional plasmonic materials are noble metals, such as gold and silver, but they have some limitations that may hinder their application in plasmonic devices, such as lack of the chemical stability in air, difficulty in modulating by external field, large optical losses in the infrared wavelength range, etc. It has been demonstrated that transparent conducting oxides are a good candidate of plasmonic materials working in the infrared frequency range because of their low optical loss and tenability. Here in this work, the quasi-three dimensional silica nano-sphere array is prepared by nano-imprint lithography. Indium tin oxide (ITO) film is deposited on the array. The transmission properties are measured and the excitation modes of surface plasmons are analyzed for the samples obtained. Then, we focus on the effect of annealing treatment on characteristics of surface plasmon resonance for ITO thin films. The carrier concentration and carrier mobility of the ITO thin films annealed under different conditions are changed, and the corresponding surface plasmon resonance characteristics are investigated. The main results obtained in this work are as follows. 1) Mono-disperse SiO2 spheres, quasi-ordered monolayer SiO2 mask and ITO films with high transmittance ( 85%) and high electrical conductivity are obtained. Experimental results show that a surface plasma resonance at a wavelength of 1780 nm is excited for the glass/sphere/ITO system. 2) The grain size of ITO thin film after being annealed turns large, resulting in the increased optical transmittance of samples. 3) The carrier concentration of ITO film annealed in the air decreases, leading the resonance peak of surface plasmon to be red-shifted. 4) The carrier concentration of ITO thin film annealed in vacuum increases and the resonance peak is blue-shifted. These results obtained in this work contribute to the application of surface plasmon devices fabricated by ITO materials.