Physicochemical Properties of Spray-Deposited CoFe2O4 Thin Films
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Cobalt ferrite thin films are deposited onto quartz glass substrates by chemical spray pyrolysis technique at different substrate temperatures using ferric nitrate and cobalt nitrate as precursors. Thermogravimetric analysis (TGA) study indicates the formation of CoFe2O4 by decomposition of cobalt and ferric nitrates after 800 °C. X-ray diffraction studies reveal that annealed films are polycrystalline in nature and exhibit spinel cubic crystal structure. Crystallite size varies from 39 to 44 nm with the substrate temperatures. Direct optical band gap energy of CoFe2O4 thin films is found to be 2.57 eV. The AFM images show that roughness and grain size of the CoFe2O4 thin film are about 9 and 138 nm, respectively. The measured DC resistivity of the deposited thin films indicates that as temperature increases the resistivity decreases indicating the semiconductor nature of the films. Decrease in dielectric constant (ε′) and loss tangent (tanδ) has been observed with frequency and attains the constant value at higher frequencies. The AC conductivity of cobalt ferrite thin films increases with increase in frequency. Thus, the prepared films show normal dielectric performance of the spinel ferrite thin film. Room-temperature complex impedance spectra show the incomplete semicircles as films exhibit high resistance values at lower frequencies.
KeywordsAFM CoFe2O4 thin films dielectric properties spray pyrolysis temperature
Authors are very thankful to the council of scientific and industrial research (CSIR), New Delhi, for the financial support through its Project No. “03(1284)/13/EMR-II.” Also authors are very thankful to the University Grants Commission (UGC), New Delhi, for the financial support through its Project No. “41-869/2012 (SR)”. One of the author V.V. Ganbavle is thankful to University Grants Commission, New Delhi for providing financial support through UGC-BSR fellowship.
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