Pulsed laser deposited CoFe 2 O 4 thin films as supercapacitor electrodes.

The influence of the substrate temperature on pulsed laser deposited (PLD) CoFe 2 O 4 thin films for supercapacitor electrodes was thoroughly investigated. X-ray diffractometry and Raman spectroscopic analyses confirmed the formation of CoFe 2 O 4 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 CoFe 2 O 4 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 CoFe 2 O 4 along with the fast electron and ion transport at the surface.