High-Performance Flexible ZnO Thin-Film Transistors by Atomic Layer Deposition

Abstract

Flexible zinc oxide thin film transistors (ZnO TFTs) with a mobility of 13 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V · s and an I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> ratio of 1.5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> have been fabricated on polyimide substrate, where the ZnO channel is deposited by atomic layer deposition (ALD) at 140 °C. High bending stability has been achieved due to excellent interface quality between alumina (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) dielectric and ZnO channel with a sharp interface topography. The flexible ZnO device exhibits excellent electrical characteristics even after being bent for 200 000 cycles with a tensile strain of 0.63%. Electrical measurement under a high tensile strain of 2.08% has also been carried out. Moreover, the electrical performance dependence of flexible ZnO TFTs with a tensile strain of 0.78% on temperature from 20 °C to 140 °C has been investigated for the first time.