Characteristics of flexographic printed indium–zinc-oxide thin films as an active semiconductor layer in thin film field-effect transistors

Abstract

Characteristics of oxide semiconductor thin film transistors prepared by flexographic printing technique have been studied. The device was a field-effect transistor substrate (15mm×15mm, n-doped silicon, 90nm SiO2 layer) with pre-structured gold electrodes and a printed active layer. The active layer was printed with a indium–zinc-oxide precursor solution and then annealed at 450°C for 4min on a hotplate. Influences of typographical parameters, i.e. printing pressure, anilox roller pressure, ink supply rate, printing velocity and printing plate (cliché) properties were studied. Reference active layers were produced by spin coating. The printed IZO ceramic layer with a dry film thickness between 3 and 8nm, deposited onto the substrate for field-effect transistors provided a good performance with charge carrier mobilities (μ) up to 2.4cm2V−1s−1, on/off current ratios (Ion/off ratio) up to 5.2×107 and mean threshold voltages (Vth) of +4V. The characterization of the printed and annealed IZO layer by AFM revealed the amorphous nature of the printed active layer films with a root-mean square roughness of 0.8nm.