Pulsed laser deposition of manganese oxide thin films for supercapacitor applications

Abstract

Thin films of manganese oxides have been grown by the pulsed laser deposition (PLD) process on silicon wafer and stainless steel substrates at different substrate temperatures and oxygen gas pressures. By proper selection of processing parameters such as temperature and oxygen pressure during the PLD process, pure crystalline phases of Mn2O3, Mn3O4 as well as amorphous phase of MnOx were successfully fabricated as identified by X-ray diffraction. The pseudo-capacitance behaviours of these different phases of manganese oxides have also been evaluated by the electrochemical cyclic voltammetry measured in 0.1M Na2SO4 aqueous electrolyte at different scan rates. Their specific current and capacitance determined by electrochemical measurements were compared and the results show that crystalline Mn2O3 phase has the highest specific current and capacitance, while the values for crystalline Mn3O4 films are the lowest. The specific current and capacitance values of the amorphous MnOx films are lower than Mn2O3 but higher than Mn3O4. The specific capacitance of Mn2O3 films of 120nm thick reaches 210Fg−1 at 1mVs−1 scan rate with excellent stability and cyclic durability. This work has demonstrated that PLD is a very promising technique for screening high performance active materials for supercapacitor applications due to its excellent flexibility and capability of easily controlling chemical composition, microstructures and phases of materials.