Aqueous solution deposition of indium hydroxide and indium oxide columnar type thin films

Crystalline In(OH)3 and UV-emitting In2O3 thin films with a unique columnar morphology have been successfully prepared for the first time via a simple aqueous solution deposition method. In the present study, sulfonate-terminated self-assembled monolayers on single-crystal Si wafers were used as substrates for the film deposition. Uniform In(OH)3 thin films formed on self-assembled monolayers in aqueous solutions of InCl3 · 4 H2O at 60 °C. These films, containing columnar In(OH)3 crystals, showed preferential growth orientation along the [100] direction. The current understanding of the film formation mechanism was discussed. After annealing in air at 400 °C, these films were converted to nanocrystalline In2O3 films without modification of the morphology. Photoluminescence emission from In2O3 films was reported at approximately 3.4 eV, which was ascribed to the near-band-edge emission.