Gas sensing and opto-electronic properties of spray deposited cobalt doped CdO thin films

Present work is focused on the improvement of gas sensing and opto-electronic properties of cadmium oxide (CdO) thin films deposited by chemical spray pyrolysis technique, with different cobalt (Co) dopant concentrations in the final spray solution. The XRD patterns reveal that the preferential growth is shifted between (111) and (200) depending on the Co- doping concentrations. The Cd-O bond vibrations were confirmed by micro-Raman analysis. The oxidization state of metal elements was determined by XPS analysis. The FE-SEM analysis revealed the variation in surface microstructure due to the variation in Co- doping concentration in CdO thin films. The elemental composition of deposited films was estimated using EDS. The formaldehyde gas response of 0.50 wt% Co- doped CdO thin film was 23%. The electrical properties were estimated by Hall measurements in van der Pauw configuration. The 0.50 wt% Co- doped CdO thin film showed a maximum carrier mobility of about 87 cm2/Vs and a photocurrent of 2.50 nA at 42 V. The Co- doped CdO thin films showed a high optical transmittance of about 84% in the range of 600-1100 nm. The band gap varies between 2.38 eV and 2.50 eV. The estimated high figure of merit is 4.79 × 10−3 Ω−1 for 0.50 wt% of Co- doped CdO film.