Flexible zinc oxide thin-film transistors using oxide buffer layers on polyethylene napthalate substrates

We report on the fabrication and characterization of flexible ZnO thin-film transistors (TFTs) using multilayer oxide buffer layers. ZnO-TFTs on polyethylene napthalate (PEN) substrates were fabricated by pulsed laser deposition (PLD) at room temperature (RT). ZnO films were characterized by Hall effect measurements. The electron mobility and the carrier density were 52.4 cm²/Vs and 3.2×10¹⁷ cm^-3. Top-gate-type TFTs were fabricated from a thin film of HfO₂ dielectric as a high-k material gate insulator. A transconductance, g_m, of 1.7 mS/mm, an on/off-current ratio of 2.4×10⁶ and a threshold voltage, V_th, of -1.2 V were achieved for a ZnO TFT with a SiO₂/TiO₂ buffer layer.