Transparent conducting yttrium-doped ZnO thin films deposited by sol–gel method

Abstract

Transparent and conductive high preferential c-axis oriented ZnO thin films doped with yttrium have been prepared by sol–gel method using zinc acetate and yttrium chloride as cations source, 2-methoxyethanol as solvent and monoethanolamine (MEA) as sol stabilizer. Film deposition was performed by dip-coating technique at a withdrawal rate of 6.0 cm/min on silica glass substrates. The effect of dopant (Y) concentration, heating treatment and annealing in a reducing atmosphere on the structure, morphology, electrical and optical properties of ZnO thin films were investigated. When compared with the resistivity values of films without the annealing treatment, the values of films annealed in the reducing atmosphere were decreased by about three orders of magnitude. The lowest resistivity value was 6.75 × 10 − 3 Ω cm, which was obtained in the 0.5 at.% yttrium-doped ZnO thin film annealed in nitrogen with 5% hydrogen at 500 °C. The average optical transmittance values of the annealed films were more than 80% in the visible range. The energy band gap calculated from the transmittance spectra is about 3.30–3.37 eV.