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The solution processing of metal–oxide–semiconductor devices is a less energy-intensive route for fabricating transparent, high-performance electronics for the display industry. On the other hand, the poor long-term stability of these solution-processed thin films limits their wide-scale adoption. One possible way of improving the stability of the devices is doping the semiconductor film with another metal oxide. This letter reports the fabrication of solution-processed indium oxide films with and without molybdenum (VI) oxide doping and the device characteristics immediately after fabrication and after 30 days of storage. The results showed that the transistor devices with a pristine indium oxide thin film exhibit a severe drop in the ON-current level and charge carrier mobility and a large change in the threshold voltage. When molybdenum ions were included in the thin film, significant improvement was achieved in the stability of the electronic performance characteristics of the device in terms of the charge carrier mobility and threshold voltage.

Recently, reducing the operating voltage of metal oxide transistors has become a priority because this enables their use in wearable electronics where low power consumption is a requirement. Here, we fabricate transistors that operate under low driving voltage after adding a solution-processed, tungsten-doped indium oxide (IWO) semiconductor deposited on top of a 20 nm aluminum oxide transparent high-k dielectric. To analyze the effect of the tungsten content on the characteristics of IWO thin film transistors (TFTs), devices based on films with 0.11, 0.22, and 0.34 mol% tungsten content were fabricated and compared to pristine indium oxide-based TFTs. Optimized tungsten (W) content at 0.11 mol% achieves a fivefold improvement in the charge carrier mobility, an ON/ OFF current ratio two orders of magnitude higher, and the subthreshold swing decreased to less than 0.1 V/dec. The bias stability of the device with optimal W concentration is also significantly better than undoped In2O3-based TFTs, probably because doping effectively suppresses the generation of oxygen vacancies in the IWO active channel layer and improves device stability. To test the feasibility of IWO devices in practical applications, a load-type inverter was fabricated using the optimally doped film.

Solution processing is a promising alternative to fabricate transparent metal oxide layers for display applications. One drawback is poor bias stability of the devices with as-deposited films. Here, we report on the postdeposition treatment of solution-processed indium oxide (In2O3) thin-film transistors (TFTs) performed by a helical-focused plasma source. The RF generator power of the plasma source is varied to optimize the treatment conditions. The electrical performance of the In2O3 TFTs showed improvement after treatment at lower and medium RF power, but when increased to 180 W, no transistor operation was observed. The best bias stability based on current deterioration and threshold voltage shift was observed when the RF power of the plasma generator was set to 60 W. The oxide films were further studied by measuring the optical absorbance, performing atomic force microscopy to analyze the surface roughness, and measuring the water contact angle to assess the hydrophilicity. A resistive load-type inverter was constructed by connecting optimized In2O3 TFTs with a resistor of 20 $\text{M}\Omega $ and the inversion characteristics were assessed.