Synthesis and Properties of (Bi, Cd)-doped CuMn2O4 thin films by sol-gel dip-coating method

In the present experimental research work, thin films of pure and (Bi,Cd)-doped CuMn2O4 have been deposited onto pyrex glass substrates at optimized substrate temperature of 500 degrees C, using sol-gel dip-coating method. The copper nitrate, manganese nitrate, bismuth nitrate and cadmium nitrate were used as precursor materials with distilled water as solvent. Deposited thin films were studied using X-ray diffraction, absorption UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and impedance spectroscopy. The X-ray diffraction pattern indicated a copper manganite (CuMn2O4) spinel structure. The crystallite size determined using Debye-Scherrer's formula, increased with increasing the Bi and Cd concentration and found in the range of 19,46-52,32 nm. FTIR spectrum depicted the presence of two distinct bands at 663.5 cm-1and 567 cm-1 characterizing CuMn2O4 spinel-type structure. Thin films have the best absorbance in the ultra-violet and blue regions. The highest absorbance observed was for the Cd-doped sample at 6%. Moreover, the optical energy band gaps (Eg) of deposited thin films determined by Tauc's relation decreases with addition of Bi and Cd content. The impedance spectra (Nyquist plots) of the films show semicircle arcs and the electrical resistance of the thin films was reduced from 81.6 to 31.20 Omega for the doped Bi and from 81.6 to 43.62 Omega for the doped Cd. An RC electrical equivalent circuit can be proposed. Thus, our results indicate the possibility of developing semiconductor materials with a spinel structure having interesting optoelectrical properties for different technological applications.