Optical study and simulation of diffusion of copper ions in the linbo3 crystal

The article deals with research into the processes of diffusion and drift of copper ions in a lithium niobate crystal after annealing in the presence of a copper film deposited on the crystal surface. For this purpose, there are chosen temperatures T = 600, 650, 700, 750 and 800°C, with the duration of high-temperature annealing being 6 hours for each sample. The optical absorption spectra of the samples are recorded in the direction perpendicular to the direction of diffusion at different distances from the edge of the crystal. Absorption bands of Cu⁺ (400 nm) and Cu²⁺ (1000 nm) ions are observed in all the samples annealed. The intensity of the bands varies depending on the annealing temperature and the distance from the diffusion source. Concentrations of copper ions are calculated using the Smakula–Dexter formula. Depth dependences of the Cu ions concentration are approximated within the framework of the model, taking into account both diffusion and drift of Cu ions. Experimental spatial distributions of copper ion concentrations are well approximated by theoretical curves calculated within the framework of the mathematical model of diffusion. The diffusion coefficients determined from the approximations are well-agreed with the available data from the literature.