Highly transparent and lower resistivity of yttrium doped ZnO thin films grown on quartz glass by sol-gel method

Abstract

We prepared highly transparent yttrium-doped ZnO (YZO) thin films on quartz glass by a sol gel method, and then annealed them at 600 degrees C in vacuum. All samples showed hexagonal wurtzite structure with a preferential orientation along the (002) direction. We observed the average grain size of Y: 2 at% thin film to be in the range of 15-20 nm. We observed blue shift in the optical bandgap (3.29 eV -> 3.32 eV) by increasing the Y concentration (0-2 at%), due to increasing the number of electrons, and replacing the divalent (Zn2+) with tri-valent (Y3+) dopants. Replacing the higher ionic radii (Y3+) with smaller ionic radii (Zn2+) expanded the local volume of the lattice, which reduced the lattice defects, and increased the intensity ratio of NBE/DLE emission (I(NBE)r/I-DLE). We also observed the lowest (172 meV) Urbach energy of Y: 2 at% thin film, and confirmed the high structural quality. Incorporation of the appropriate Y concentration (2 at%) improved the crystallinity of YZO thin films, which led to less carrier scattering and lower resistivity. (C) 2016 Elsevier B.V. All rights reserved.