Optical properties and photoconductivity of amorphous silicon carbon nitride thin film and its application for UV detection

Optical properties of amorphous silicon carbon nitride thin films as a function of carbon content have been studied by the spectral microreflectometry. The compositions of a-SiCN thin films deposited with different CH4 flow rates were analyzed by X-ray photoemission spectroscopy (XPS). It was found that the transmittance of a-SiCN thin films decreases with the increasing carbon content; the index of refraction n varies from ~2.0 to ~2.2 and the optical gap (Tauc gap) Eopt value progressively decreases from 4.1 to 3.3 eV while the carbon content changes from 0 to 25% in the films. In addition, a MSM (metal-semiconductor-metal) photodetector device based on the a-SiCN thin film demonstrates excellent selective sensing features with a large photo-to-dark current ratio about 1800 under illumination of the 250 nm UV light source, providing potential applications for low-cost UV detection. D 2004 Elsevier B.V. All rights reserved.