Low-temperature combustion synthesis and UV treatment processed p-type Li:NiOx active semiconductors for high-performance electronics

Abstract

Solution-processed thin film transistors (TFTs) in the next generation of large-area flexible electrics not only need oxide semiconductors with high performance but also require them with low-temperature processability. To meet these requirements, we developed a low-temperature method, that is, combining solution combustion synthesis and deep-ultraviolet irradiation to prepare p-type Li-doped NiO_x (Li:NiO_x) thin films at 150 °C. The incorporation of Li into the NiO_x matrix significantly improves p-type conductivity of NiO_x because the Fermi level (E_F) shifts toward the valence band maximum. To confirm the possible application of Li:NiO_x as the channel layer in TFTs, Li:NiO_x/ZrO₂/ITO was fabricated on each of rigid glass and flexible PET substrates. This is the first report of application of Li:NiO_x semiconductor in TFT devices. The field-effect mobility, I_on/I_off and subthreshold swing for rigid and flexible Li_5%:NiO_x TFTs are 1.69 and 1.41 cm² V⁻¹ s⁻¹, 8 × 10⁶ and 10⁵, 0.21 and 0.54 V dec⁻¹, respectively. Furthermore, the counterclockwise hysteresis of transfer curves is negligible (0.1 V). Thus, the high-performance and cost-effective electronics with low fabrication temperature will definitely contribute to future large-scale flexible and wearable electronics.