Effect of EDTA on cadmium sulfide thin films for oxygen gas sensor applications

The cadmium sulfide/ethylenediamine tetraacetic acid (CdS/EDTA) nanostructure thin film was prepared on a glass substrate using sol-gel spin-coating method and used for gas sensor applications. The structure of the CdS and CdS/EDTA thin films were characterized. The nanostructured thin film was found both in hexagonal and cubic structure with an average crystallite size of 43 nm. The stretching vibration mode of CdS and CdS/EDTA was confirmed through fourier transform infrared spectroscopy (FTIR). The surface morphology of the CdS and EDTA doped CdS thin film was investigated using scanning electron microscope (SEM). The EDTA doped CdS surface found to be crystalline with random orientation of particles as compared with that of CdS without EDTA. The values of band gap energy for CdS and CdS/EDTA were obtained respectively, 4.20 and 4.17 eV. The photoluminescence (PL) spectra of the CdS and CdS/EDTA thin film exhibited respectively, green and yellow band emissions. Oxygen gas was suitably tailored to verify the sensor response over a concentration range of 20-100 ppm at room temperature. The observed results reveal that the performance, response and recovery time of sensors found to be increased with the addition of chelating agent to CdS.