Lecture
WEB Spatial changes of optical and mechanical properties of lithium niobate single crystals doped by copper ions
Tuesday (22.09.2020) 11:50 - 12:05 F: Functional Materials, Surfaces, and Devices 2 Part of:Despite the widespread use of lithium niobate (LN), searching for ways to improve their characteristics is an urgent task [1]. High temperature annealing of LN in the presence of metal ions is one of the techniques of modifying of surface layers of LN which is extensively used to create LiNbO3-based elements for functional electronics. In particular, such modification leads to a change of the optical and mechanical properties of LN [2].
The purpose of this work is a comparative investigation of optical and mechanical properties changes of diffusion layers of copper doped LiNbO3. Copper was chosen because it is successfully used for increase of the photorefractive sensitivity of LN as well as for creation of planar waveguides. It should also be mentioned that under the same conditions, the diffusion coefficient of copper in LN is about 500 times higher than the one, for example, of Fe [3].
The oriented crystal was annealed in the presence of CuO for 21 h. at 1073 K. The optical absorption spectra of the LiNbO3:Cu single crystals were recorded in a direction perpendicular to the direction of diffusion at different distances from the crystal edge. The spectra were recorded consecutively along the crystal-physics directions X, Y, and Z (the diffusion directions) with the 20 μm step [4]. The mechanical properties of modified diffusion layers in LN were determined by a Nano Indenter (CSM Instruments SA, Switzerland). Scanning was carried out in X and Z crystallographic directions, at that the indenter presses on a plate in the crystal-physics direction Y. It is established that the changes of optical (absorption) and mechanical (hardness) properties are correlated and are related to the spatial distribution of Cu ions. The diffusion depth of Cu in our experiments is about 600 μm. The mechanism of the lithium niobate crystal layers modification by the diffusion of copper is discussed.
