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

• Published in: Sensors and actuators. B, Chemical Chemical, 2018-02, Vol.255, p.871-883
• Main Authors: Velusamy, P., Babu, R. Ramesh, Ramamurthi, K., Elangovan, E., Viegas, J., Sridharan, M.
• Format: Article
• Language: English
• Subjects: Cadmium; Carrier mobility; Cobalt; Doping; Electric properties; Electrical properties; Energy gap; Figure of merit; Gas sensing properties; Gas sensors; Microstructure; Optical properties; Optoelectronics; Organic chemistry; Photoelectric effect; Photoelectric emission; Photonic band gaps; Spray deposition; Spray pyrolysis; Surface morphology; Thin films; X ray photoelectron spectroscopy; X-ray diffraction
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2017.08.147

•For the first time, we have prepared undoped and Co- doped CdO thin films using a simple homemade chemical spray pyrolysis setup.•The high formaldehyde gas sensing (23%) is observed for 0.50wt% Co- doped CdO thin film.•The 0.50wt% Co- doped CdO thin film has high optical transparency (84%) than that of undoped CdO (72%).•The high figure of merit (4.79×10−3Ω−1) is obtained for 0.50wt% of Co doped CdO thin film. 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 0.50wt% Co- doped CdO thin film was 23%. The electrical properties were estimated by Hall measurements in van der Pauw configuration. The 0.50wt% Co- doped CdO thin film showed a maximum carrier mobility of about 87cm2/Vs and a photocurrent of 2.50nA at 42V. The Co- doped CdO thin films showed a high optical transmittance of about 84% in the range of 600–1100nm. The band gap varies between 2.38eV and 2.50eV. The estimated high figure of merit is 4.79×10−3Ω−1 for 0.50wt% of Co- doped CdO film.