Dielectric Properties of SnO 2 Thin Film Using SPR Technique for Gas Sensing Applications

Focus has been made on the determination of dielectric constant of thin dielectric layer (SnO 2 thin film) using surface plasmon resonance (SPR) technique and exploiting it for the detection of NH 3 gas. SnO 2 thin film has been deposited by rf-sputtering technique on gold coated glass prism (BK-7) and its SPR response was measured in the Kretschmann configuration of attenuated total reflection using a p-polarised light beam at 633 nm wavelength. The SPR response of bilayer film was fitted with Fresnel’s equations in order to calculate the dielectric constant of SnO 2 thin film. The air/SnO 2 /Au/prim system has been utilized for detecting varying concentration (500 ppm to 2000 ppm) of NH 3 gas at room temperature using SPR technique. SPR curve shows significant shift in resonance angle from 44.8° to 56.7° on exposure of fixed concentration of NH 3 gas (500 ppm to 2000 ppm) with very fast response and recovery speeds.