Fabrication of the Mn3O4 thin film electrodes by electron beam evaporation for supercapacitor applications

Electron beam evaporation technique has been employed for the fabrication ofMn(3)O(4)thin films on various substrates such as Pyrex Glass (PG), Stainless Steel (SS) and Au/Ti/SiO2/(textured) Silicon (ATS). The structural properties of as deposited Mn3O4 films are investigated using XRD, Raman spectroscopy, SEM, EDS and AFM. The optical properties of Mn(3)O(4 )films are studied for the films deposited on PG substrates. The electrochemical performance of Mn3O4 films deposited on SS and ATS substrates are examined by Cyclic Voltammetry, Chronopotentiometry and Electrochemical Impedance Spectroscopy. The films grown on PG, SS and ATS substrates are poor crystalline, polycrystalline and crystalline in nature, respectively. The major Raman peak at 654 cm(-1) and FTIR absorption peak at 624 cm(-1) confirm the existence of Mn-O bonding. The SEM and AFM analysis revealed that the films deposited on PG, SS and ATS substrates covered with non-uniform spherical grains, flakes like grains and well dispersed pyramidal grains, respectively. The optical band gap of the films grown on PG substrates is 2.86 eV. The films deposited on ATS substrates exhibited superior electrochemical properties by offering the high specific capacitance of 754 F g(-1) at a specific current of 1 A g(-1)and good cycling retention (89%) even after 4000 cycles. The specific capacitance and cycling performance are further improved after annealing the films in a controlled oxygen ambience. Prime novelty statement: Mn3O4 thin film micro electrodes were prepared on Au/Ti/SiO2/Si substrates. Further to improve the structural and morphological features of the films, the films were annealed at different temperatures. The improved electrochemical performance in terms of discharge specific capacitance and cycling stability is correlated with microstructure. (C) 2019 Elsevier B.V. All rights reserved.