Electrochemical Degradation Mechanism of Transparent Conductive Indium Tin Oxide Film in HCl Solution

Purpose: In order to offer a better understanding of the root causes of the electrochemical corrosion failure of indium tin oxide (ITO), the degradation mechanism was investigated with specific attention to changes in chemical composition and the crystalline phase, and then correlated with electrical resistance and optical transparency of the ITO film.BRMethods: An electrochemical polarization test was carried out in 1M HCl solution. For the interrupted specimens after specific corrosion times, various analytical characterizations were performed including scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, electrical resistance, and optical transmittance.BRResults: The polarization curve was divided into four distinct stages based on the varying electrochemical behaviors and the resulting changes in morphology/phase evolution were investigated. ITO film was corroded by breaking of In-O bonds followed by reduction of In3+ and Sn2+ ions. The reaction terminated with the formation of In-Cl particles as byproducts of corrosion. Electrical conductivity decreased abruptly with the dissolution of ITO film, and 5–10% variation in optical transparency of the ITO film was also recorded in response to the electrochemical activity.BRConclusion: Based on the chemical composition and phase analysis for the interrupted specimens at specific stages, the electrochemical corrosion mechanism was proposed, and this material degradation mechanism was correlated with that of the electrical resistance and optical conductivity, respectively.