Samarium-doped ZnO thin films synthesized by Sol-gel: Structural, optical and electrical properties

Abstract

Zinc oxide thin films doped with various elements are in the spotlight due to their electrical, thermoelectrical, luminescent and transparency in the visible range properties, with multiple applications in optoelectronic devices. In this work, samarium doped zinc oxide thin films were prepared by the Sol-gel technique, from a very simple solution. Only the metal precursors (zinc acetate and samarium nitrate) were dissolved in methanol at room temperature. A completely transparent, homogeneous and stable solution was obtained without the need of additives, stabilizers or catalysts of any kind. Thin films were prepared using a multi-dipping procedure on Corning glass substrates. The doping concentrations were 3 and 5 at.% and the annealing temperature varied from 100 to 500 °C. The films were characterized by XRD, FTIR, UV–Vis and SEM; the thickness and resistivity of the films were also measured. According to the XRD results, all the films are polycrystalline and nanostructured, even when annealed at 100 °C, a considerably low temperature. The electrical properties of the films and their high optical transmission (>80%) in the visible-near IR range, render these nanocrystalline films potential materials for their use in optoelectronic devices. A figure of merit (ϕ) of 3.5 × 10−6 Ω−1 was obtained for the 3 at.% ZnO:Sm films annealed at 400 °C, which also confirmed the beneficial effects of the samarium dopant in the ZnO matrix.