Experimental and computational probes on Er-doped LiTaO3 as Near-Infrared Detectors

Er-doped lithium tantalate (LiTaO3) is an emerging photoluminescent material with excellent emissivity in both visible and near infrared wavelengths. We present DFT calculations for LiTaO3 doped with Er with substitution of Li and Ta ions at 4.167 mol %. Based on calculations, nanoparticles of LiTaO3 containing 0.5-10 mol. % erbium were synthesized using modified wet chemical synthesis. The traditional methods of preparation require high temperature annealing and lead to large particle size due to agglomeration at calcinating temperatures. To receive nanoparticles, the commercially sold micro-sized tantalum pentoxide is transformed into nano-sized particles with 48% HF in a water bath at an average temperature of 80°C for 8 hours, and is subsequently neutralized with 30% Ammonium hydroxide, washed with deionized water, and dried at 100°C for 12 hours. The nano-sized tantalum oxide is milled in a high-energy ball mill with a stoichiometric amount of lithium hydroxide and 0.5-10 mol.% erbium oxide. The thermogravmetric analysis showed that Er-doped LiTaO3 at nanoscale can be received at lower temperature, based on which the mixture was calcinated at 650°C for 4 hours. XRD analysis showed no peak shifts between the host LiTaO3 and its doped counterparts. The SEM reveals average size of 100 nanometers for the product. The product containing 3 mol. % Er shows stronger visible photoluminescence emission compared to the system containing 0.5 % and 10 % Er, while the system with 0.5 mol. % Er demonstrates improved near IR emission compared to both 3% and 10% Er doped LiTaO3. The electronic structure was also calculated using the hybrid functional HSE06 which accurately shows the location in energy of the individual 4f orbitals and allowed interband transition assignments, which agreed with the emissions from the photoluminescence measurements.