Direct Photopatterning of Solution-Processed Amorphous Indium Zinc Oxide and Zinc Tin Oxide Semiconductors-A Chimie Douce Molecular Precursor Approach to Thin Film Electronic Oxides

Direct photopatterning of indium zinc oxide (IZO) and zinc tin oxide (ZTO) semiconductors is realized using Schiff-base complexes of indium, zinc, and tin(II) with methoxyiminopropionato ligands as precursors. These precursor complexes are stable under visible light, but they interestingly decompose in the UV region, thereby facilitating a site-selective photopatterning and its subsequent conversion to the desired amorphous oxides. Thin film transistors (TFTs) with photopatterned IZO and ZTO layers exhibit high performance after post-annealing at relatively low temperatures between 250 and 350 degrees C, with charge-carrier mobilities (mu(sat)) of 7.8 and 3.6 cm(2) (V s)(-1) for IZO and ZTO, respectively. The mechanism of the photodecomposition of the precursor films is studied by attenuated total reflectance-Infrared spectroscopy. Apart from the electrical characterization, the resultant UV-patterned oxide thin films are characterized by transmission electron microscopy micrographs of focussed ion beam (FIB)-prepared cross sections, atomic force microscopy, as well as Auger depth profiles. X-ray photoelectron spectroscopy investigations elucidate the influence of surface hydroxylation on the TFT performance. The straightforward approach of facile precursor UV-photopatterning demonstrates its potential feasibility as a low-cost method toward integration of such solution-processed oxide films into large-area electronics.