Thin films grown via atomic layer deposition (ALD) suffer from insufficient growth rate and unreliability for temperature-sensitive electronic substrates. This study aimed to examine the growth characteristics and dielectric strength of ALD Al₂O₃ films grown at low temperatures (≤ 150 °C) for potential application in flexible electronic devices. The growth rate of the Al₂O₃ films increased from 0.9 to 1.1 Å/cycle with increasing temperature and saturated at growth temperatures ≥ 150 °C, which is the critical temperature at which a complete oxidation reaction occurred. The dielectric strength was also improved with increasing growth temperature, and the films grown at 150 °C showed a high breakdown field strength (~ 8.3 MV/cm), attributable to the decrease in the carbon impurities and oxygen defects, as confirmed by X-ray photoelectron spectroscopy. Even at low growth temperatures (≤ 150 °C), ALD Al₂O₃ films showed an overall amorphous structure and extremely smooth surfaces regardless of the growth temperature.

This minireview summarizes the latest progress on the interface engineering for solid oxide fuel cells using atomic layer deposition and provides a perspective on directions for further development.

A HfO ₂ film was grown using discrete feeding ALD, an advanced ALD process designed to improve the surface coverage of the precursor, which decreased the residual impurities in the film and increased the film density.

The properties of Al-doped SnO_x films deposited via reactive co-sputtering were examined in terms of their potential applications for the fabrication of transparent and flexible electronic devices. Al 2.2-atom %-doped SnO_x thin-film transistors (TFTs) exhibit improved semiconductor characteristics compared to non-doped films, with a lower sub-threshold swing of ~0.68 Vdec⁻¹, increased on/off current ratio of ~8 × 10⁷, threshold voltage (V_th) near 0 V, and markedly reduced (by 81%) V_th instability in air, attributable to the decrease in oxygen vacancy defects induced by the strong oxidizing potential of Al. Al-doped SnO_x films maintain amorphous crystallinity, an optical transmittance of ~97%, and an adhesive strength (to a plastic substrate) of over 0.7 kgf/mm; such films are thus promising semiconductor candidates for fabrication of transparent flexible TFTs.

Abnormal hysteresis was found to exist in amorphous Hf-In-Zn-O thin film transistors under illumination. Unlike common hysteresis, a disparity in the sub-threshold swing of the transfer curves was observed. This distinction showed a linear increase according to light intensity, and is thought to come from the light enabled motion of ionized oxygen vacancies (V_{O 2+}). The positively charged nature of these defects causes them to show a different distribution in the channel according to sweep direction. The hysteresis decreased when the sweep range was decreased, and vanished when the sweep range fell in the positive region only.