Structural, morphological, and opto-electrical characterization of Mn and Co doped CuO thin films

Abstract

Pure, Co and Mn doped CuO thin films are synthesized onto glass substrate by spray pyrolysis technique (SPT) at 350°C substrate temperature. Concentration of Co and Mn are varied as 2,4,6,8 at.%. The effect of change of doping concentration of Co and Mn on the structural, optical and electrical properties of the CuO thin film is studied. Field emission scanning electron microscopy (FESEM) is used to study the surface morphology of CuO, CuO:Co and CuO:Mn thin films. The FESEM images show that the surface of the pure CuO thin film is comprised of irregular shaped nanoparticles. For Co doping worm like agglomerates are formed and for Mn doping flower like structures are found in the CuO film surface. Energy dispersive X-Ray (EDX) analysis confirms the compositions and stoichiometry of CuO, CuO:Co and CuO:Mn thin films. Quantitative analysis shows that at.% of Co and Mn increases with the increase of Co and Mn concentration in CuO:Co and CuO:Mn thin films. X-Ray diffraction (XRD) patterns of CuO,CuO:Co and CuO:Mn thin films show monoclinic structure which remains unchanged up to 2 at.% Mn doping and 4 at.% Co doping. (1 ̅11) is the prominent peak. Crystallite size of the thin films varies from 25.54-34.00 nm. Transmittance of CuO, CuO:Co and CuO:Mn thin films are measured by UV-visible spectroscopy and optical band gap is calculated from those data. Transmittance of CuO thin films decreases with Co concentrations between 0 to 8 at.%. Transmittance decreases with Mn concentrations between 4 to 8 at.%. The maximum transmittance is found 90% for 2 at.% Mn doped CuO thin film. The direct band gap of CuO thin film is found to be 3.00 eV. Band gap decreases with increasing Co concentrations, the minimum band gap is found to be 1.98 eV for 8 at.% CuO:Co thin film. Band gap decreases with the Mn doping from 0 to 4 at.% then increases for 6 at.% and again decreases for 8 at.% Mn. The minimum band gap is found to be 2.31 eV for 4 at.% CuO:Mn thin film. Electrical resistivity of CuO, CuO:Co and CuO:Mn thin films are measured at room temperature by linear four point prob method. The resistivity is found of the order of 103 Ω-cm. The higher resistivity found at 4 at.% CuO:Co and 8 at.% CuO:Mn thin films.