Preparation and characterization of indium oxide film by electrochemical deposition

Abstract A novel method of electrolytic Indium oxide coating has been investigated in In 2 (SO 4 ) 3 ·9H 2 O aqueous solution. Through cathodic polarization tests, three major reactions were verified: (1) O 2 + 4H + + 4e − → 2H 2 O (∼ 0.6 to − 0.25 V), (2) 2H + + 2e − → H 2 (− 0.25 to − 0.6V), (3) 2H 2 O + 2e − → H 2 + 2OH − (− 0.6 to − 1.5 V). The coated specimens obtained at the third stage were further annealed and characterized by Fourier transform infrared (FTIR), thermo-gravimetric/differential thermal analysis (TG/DTA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The TGA curve of the as-coated films was divided into four steps. The first and second were the evaporation of physical water from 2 In(OH) 3 surface between 20 and 200 °C, transformed into 2 InOOH by the removal of 2H 2 O from the gel bulk, corresponding to 10% weight loss, between 200 and 300 °C, and finally condensed into In 2 O 3 and H 2 O, corresponding to 5% weight loss, between 300 and 500 °C. From cross-sectional view, the In 2 O 3 coated film with thickness of about 100 nm revealed excellent adhesion with substrate. Particles exhibit a uniform distribution in terms of the particle shape, size and texture.