Thermal annealing effect on electrical characteristics of CuPc thin-film transistors on glass with ZrO2 as gate dielectric

Organic thin film transistors (OTFTs) with ZrO₂ as gate dielectric have been fabricated on glass substrates. The gate dielectric is annealed in N₂ at different temperatures to investigate the effects of annealing temperatures on the performance of the OTFTs. The devices show low threshold voltage and small subthreshold slope, and thus are suitable for low-voltage and low-power applications. It is also found that raising the annealing temperature can initially enhance the electrical properties of OTFTs. This is attributed to the improved dielectric and interface quality by the thermal annealing treatment. ZrO₂ annealed at 150 °C, 250 °C and 350 °C can lower the maximum density of surface states by 8 %, 32 % and 42 % respectively. Further increasing the annealing temperature to 550 °C is found to degrade the device performance. Among the studied devices, OTFTs with ZrO₂ annealed at 350 °C exhibits the best device performance, such as a small threshold voltage of -0.89 V and a low sub-threshold slope of 1.05 V/decade.