Impact of Gd-doped on optoelectronic properties of SnO2 thin films synthesized by spin coating method

Pure and various concentrations of Gd-doped SnO 2 thin films were synthesized using a spin coating method on a glass substrate. XRD studies revealed that all the thin films exhibited polycrystalline tetragonal structures with a fundamental orientation peak along the (110) direction. The three main E g , A 1g , and B 2g vibrational modes were identified using Raman spectroscopy. XPS studies determined the oxidation states of Sn, Gd, and O. Pure SnO 2 has an average optical transmittance of 83% and it reduced significantly with Gd-doping and reached 55% in the case of a 5-at% Gd-doped film. The optical band gap energy of 4.01 eV was found in pure SnO 2 and decreased with the Gd doping, reaching 3.88 eV in a 5-at% Gd-doped SnO 2 film. The 3 at% Gd: SnO 2 and pure SnO 2 films were shown the lowest sheet resistance ( R sh ) of 33.1 Ω/Sq highest figure of merit (φ) of 2.26×10 -3 Ω -1 , respectively among others.