Performance modulation of transparent ALD indium oxide films on flexible substrates: transition between metal-like conductor and high performance semiconductor states

Abstract

Indium oxide (InO_x) films are grown by atomic layer deposition (ALD) using [1,1,1-trimethyl-N-(trimethylsilyl)silanaminato]-indium (InCA-1) as the metal precursor and hydrogen peroxide (H₂O₂) as the oxidant. It is found that the electrical properties of the indium oxide layers strongly depend on the ALD growth temperature. Relatively low electrical resistivity (∼10⁻⁴ Ω cm) and high optical transparency (>85%) are obtained at growth temperatures higher than 200 °C, which make the indium oxide film suitable for transparent conducting oxide (TCO) applications. On the other hand, at relatively low growth temperatures below 150 °C, indium oxide behaves as a transparent semiconducting oxide (TSO). Thin film transistors (TFTs) incorporating this material as the active layer exhibit reasonably high performance with saturation mobility exceeding 10 cm² V⁻¹ s⁻¹ and a threshold voltage near 0 V.