Effects of different Ar/O<inf>2</inf> ratios on the electrical properties of CuPc-based TFTs with ZrO<inf>2</inf> gate dielectric

CuPc-based TFTs with high-k dielectric ZrO ₂ as gate dielectric prepared by RF magnetron sputtering with various Ar/O ₂ ratios have been fabricated. The effects of oxygen concentration in the sputtering ambient on the electrical performance of the devices are investigated. This work finds that increasing oxygen concentration in the sputtering ambient up to a Ar/O ₂ ratio of 4:1 can improve the OTFT performance including the mobility, sub-threshold slope and on/off ratio. On the other hand, further increasing the Ar/O ₂ ratio to 4:3 is found to degrade the device performance. This demonstrates that the electrical characteristics of the devices depend strongly on the oxygen concentration in the sputtering ambient. The origin of this phenomenon is discussed.