ABSTRACT
The influence of the substrate temperature on pulsed laser deposited (PLD) CoFe2O4 thin films for supercapacitor electrodes was thoroughly investigated. X-ray diffractometry and Raman spectroscopic analyses confirmed the formation of CoFe2O4 phase for films deposited at a substrate temperature of 450 °C. Topography and surface smoothness was measured using atomic force microscopy. We observed that the films deposited at room temperature showed improved electrochemical performance and supercapacitive properties compared to those of films deposited at 450 °C. Specific capacitances of about 777.4 F g-1 and 258.5 F g-1 were obtained for electrodes deposited at RT and 450 °C, respectively, at 0.5 mA cm-2 current density. The CoFe2O4 films deposited at room temperature exhibited an excellent power density (3277 W kg-1) and energy density (17 W h kg-1). Using electrochemical impedance spectroscopy, the series resistance and charge transfer resistance were found to be 1.1 Ω and 1.5 Ω, respectively. The cyclic stability was increased up to 125% after 1500 cycles due to the increasing electroactive surface of CoFe2O4 along with the fast electron and ion transport at the surface.
ABSTRACT
Cobalt ferrite thin films were pulsed laser deposited on fused quartz substrates at different substrate temperatures and ex-situ annealed at 750 degrees C in air. Grain size of these films was found to be 6-44 nm. Magnetization of these nanocrystalline thin films was found to be dependent on the substrate temperature. Magnetization higher than the cobalt ferrite bulk value was observed in the room temperature deposited film after post deposition annealing at 750 degrees C. This could be explained on the basis of a changed cation distribution in the film caused by quenching during deposition.
ABSTRACT
Nanocrystalline magnetite thin film was prepared on to fused quartz substrate by sputtering at an rf power of 50 W. X-ray diffraction study showed that the sputtered film was (110) oriented. The stoichiometry in the thin film has been confirmed through a variety of characterization techniques. The room temperature spontaneous magnetization value (4piMs) of the film was 5100 G. This is about 85% of the bulk value. The resistivity of the film showed a sharp change around 120 K, indicative of the Verwey transition.
