Influence of Hydrothermal Temperature on the Optical Properties of Er-Doped SnO2 Nanoparticles

This work reports on crystallization and optical properties of SnO2:Er3+ with a fixed Er3+ concentration of 0.25 at.%, prepared by the hydrothermal method. Crystal structure and morphology of the materials were studied by x-ray diffraction (XRD) and field emission transmission electron microscopy. Characteristic light emission at 1.5 μm for radiative 4I13/2 → 4I15/2 transitions within the 4f electron shell of Er3+ ions was studied by photoluminescence (PL) and excitation spectroscopy. The optical bandgap of the nanoparticles was examined by ultraviolet--visible absorption measurements. SnO2:Er3+ nanoparticles were formed in single-phase tetragonal rutile structure by applying temperatures ranging from 120°C to 200°C during the hydrothermal synthesis. An average crystal size of 5 nm was estimated by the Scherrer equation using the XRD data and found to be independent from the investigated hydrothermal temperatures. Whereas, the Er3+-related PL intensities were found to increase strongly with the hydrothermal temperature.