Solution Combustion Synthesis: Low-Temperature Processing for p-Type Cu:NiO Thin Films for Transparent Electronics

Low-temperature solution processing opens a new window for the fabrication of oxide semiconductors due to its simple, low cost, and large-area uniformity. Herein, by using solution combustion synthesis (SCS), p-type Cu-doped NiO (Cu:NiO) thin films are fabricated at a temperature lower than 150 °C. The light doping of Cu substitutes the Ni site and disperses the valence band of the NiO matrix, leading to an enhanced p-type conductivity. Their integration into thin-film transistors (TFTs) demonstrates typical p-type semiconducting behavior. The optimized Cu_5%NiO TFT exhibits outstanding electrical performance with a hole mobility of 1.5 cm² V⁻¹ s⁻¹, a large on/off current ratio of ≈10⁴, and clear switching characteristics under dynamic measurements. The employment of a high-k ZrO₂ gate dielectric enables a low operating voltage (≤2 V) of the TFTs, which is critical for portable and battery-driven devices. The construction of a light-emitting-diode driving circuit demonstrates the high current control capability of the resultant TFTs. The achievement of the low-temperature-processed Cu:NiO thin films via SCS not only provides a feasible approach for low-cost flexible p-type oxide electronics but also represents a significant step toward the development of complementary metal–oxide semiconductor circuits.

A solution combustion synthesis is utilized to fabricate p-type oxide thin-film transistors (TFTs) at 150 °C. The doping of Cu into the NiO matrix can replace the Ni sites and enhance the p-type conductivity. The optimized Cu_5%NiO TFTs on both Si and ITO (indium tin oxide)/glass with ZrO₂ gate dielectrics exhibit an average hole mobility of >1 cm² V⁻¹ s⁻¹ and I_on/I_off of 10⁴.

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