Processing-phase diagrams: a new tool for solution-deposited thin-film development applied to the In5O(OPri)13–In2O3 system

Abstract

Understanding processing–property relationships of a precursor is important for achieving the desired properties in opto-electronic thin-films. This work highlights the construction of a processing-phase diagram of the novel In₂O₃ precursor In₅O(OPrⁱ)₁₃ for transparent conducting oxide applications. The decomposition behavior of the precursor was profiled with thermogravimetry, differential scanning calorimetry, and temperature programmed desorption mass spectroscopy. Decomposition occurred at 150–230 °C. Higher temperature exothermic reactions were identified as structural rearrangement/ordering processes. The precursor powder was found to crystallize into the bixbyite structure at 300–350 °C, presenting a non-crystalline phase-processing window for the material. Crystallization of a film was monitored with in situ X-ray diffraction annealing, which showed a markedly higher crystallization onset of 500 °C and a much larger non-crystalline oxide window. The decomposition and crystallization behavior of the precursor powders and films were combined into a master processing-phase diagram. Solution deposited, crystalline In₂O₃ films annealed under Ar–4%H₂ achieved a conductivity of 165 S cm⁻¹ with high visible transparency (80%) and exhibited a mobility of 9.6 cm² V⁻¹ s⁻¹ with a carrier concentration of 1.1 × 10²⁰ cm⁻³.