| Summary: | Hydrogenated polycrystalline In<sub>2</sub>O<sub>3</sub> (In<sub>2</sub>O<sub>3</sub>:H) thin-film transistors (TFTs) fabricated via the low-temperature solid-phase crystallization (SPC) process with a field-effect mobility (<i>μ</i><sub>FE</sub>) exceeding 100 cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup> are promising candidates for future electronics applications. In this study, we investigated the effects of the SPC temperature of Ar + O<sub>2</sub> + H<sub>2</sub>-sputtered In<sub>2</sub>O<sub>3</sub>:H films on the electron transport properties of In<sub>2</sub>O<sub>3</sub>:H TFTs. The In<sub>2</sub>O<sub>3</sub>:H TFT with an SPC temperature of 300 °C exhibited the best performance, having the largest <i>µ</i><sub>FE</sub> of 139.2 cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup>. In contrast, the <i>µ</i><sub>FE</sub> was slightly degraded with increasing SPC temperature (400 °C and higher). Extended X-ray absorption fine structure analysis revealed that the medium-range ordering in the In<sub>2</sub>O<sub>3</sub>:H network was further improved by annealing up to 600 °C, while a large amount of H<sub>2</sub>O was desorbed from the In<sub>2</sub>O<sub>3</sub>:H films at SPC temperatures above 400 °C, resulting in the creation of defects at grain boundaries. The threshold temperature of H<sub>2</sub>O desorption corresponded well with the carrier transport properties; the <i>µ</i><sub>FE</sub> of the TFTs started to deteriorate at SPC temperatures of 400 °C and higher. Thus, it was suggested that the hydrogen remaining in the film after SPC plays an important role in the passivation of electron traps, especially for grain boundaries, resulting in an enhancement of the <i>µ</i><sub>FE</sub> of In<sub>2</sub>O<sub>3</sub>:H TFTs.
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