Formation of indium oxide thin films fabricated by a dip-coating process using indium 2-ethylhexanoate monohydroxide

The thermal change of indium 2-ethylhexanoate monohydroxide, In(OH)(O2CCH(CH2CH3)(CH2)3CH3)2, to form indium oxide, In2O3, thin film was investigated by TG–DTA–MS in a He–20%O2 atmosphere with a minute amount of specimen (∼0.1 mg) in order to clarify the formation process of the indium-tin-oxide transparent conducting films (thickness, ∼240 nm). The total mass loss at 500 °C (67.9%) agreed approximately with the value (66.8%) corresponding to the formation of In2O3 from In(OH)(O2CCH(CH2CH3)(CH2)3CH3)2. The main mass loss at approximately 250–350 °C can be divided into two steps. In the first step, the evolution of 2-ethylhexanoic acid CH3(CH2)3(CH2CH3)CHCOOH was observed. The evolution of water vapor and carbon dioxide was observed in both steps and significant in the second step. A strong exothermic peak was also observed in the second step. A small amount of water vapor was detected at ∼130–190 °C. A reaction mechanism was proposed.