Enhanced properties of the chemically prepared Gd-doped SrSnO3 thin films: Experimental and DFT study

In the present paper, we investigate in detail the Gd doping effect on the properties of the chemically prepared SrSnO3 thin films. Unlike previous preparation attempts that utilized a very sophisticated vacuum methods and high annealing temperature, a very simple path was followed by employing the simple ultrasonic spray method with an annealing process at only 800 degrees C, resulting a high quality films. The crystallographic identification using XRD analysis confirmed the formation of SrSnO3 phase crystallizing in the orthorhombic structure with Pbnm space group. The percentage of the gadolinium doping affected the obtained structure majorly after passing the 5%. Structural properties were further investigated with Raman and FT-IR analysis confirming the results obtained by the XRD. Morphology and chemical composition of Gd-doped SrSnO3 thin films were evaluated using a field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray spectrometer (EDX). The surface scanning shows an amelioration in the morphology of the films as dopant ratio increased, while EDX and mapping analysis confirmed the purity of the resulted films with the presence of the dopant element. The Gd-doping effect on the optical properties was noticed through the decrement of the transparency of the films and the dropping of the band gap from 3.88 to 2.85 eV for the 7% of dopant content. The first principles calculations revealed a major modifications on the electronic and optical properties of SrSnO3 generated by the 4f state of Gd. A remarkable variation of the band gap was measured decreasing from 4.08 eV to 2.17 eV, which emphasizes our experimental findings.