The relevance of the solution of the problem is related to the fact that obtained results will allow to make a significant contribution to the fundamental understanding of the evolution of the ferroelectric domain structure in spatially inhomogeneous fields, which may be applied to a wide class of ferroelectric crystals, including multiaxial ferroelectric crystals.
The complex study of the domain structure formation and the revealing of the domain structure evolution in congruent lithium niobate and congruent lithium tantalate crystals, including those doped with MgO, with a surface dielectric layer under the action of electron beam will be carried out for the first time. Scientific novelty is based on the complexity of the approach in studying the domain structure formation induced by the irradiation of ferroelectric crystals by electron beam and using of complementary microscopic methods for domain visualization with high spatial resolution. The planned research will be a continuation and a significant addition to the systematic study that we started earlier. The study of polarization reversal by electron beam with surface dielectric layer and a comparative analysis of the features of the domain structure formation in previously non-investigated compositions of lithium niobate and lithium tantalate crystals will be performed. The influence of new parameters such as the crystal thickness, the energy of the electrons, the material of surface dielectric layer on the domain morphology and the evolution of the domain structure will be established. In addition, for the first time, the electron beam switching method will be used at elevated temperatures and the features of domain formation will be revealed. The spatial inhomogeneity of the created periodic domain structures (PDS) will be analyzed by the second harmonic generation method.
From a practical point of view, the claimed project related to a development of an alternative and non- contact method for the formation of PDS with given geometric dimensions. The method seems to be very promising due to the size of the electron beam can be easily scaled down to several nanometers. It will allow the transition to the submicron range of the PDS periods. In addition, the method allows to overcome all limitations of the traditional method of creating PDS such as uncontrolled domain merging and spontaneous partial backswitching and does not require additional lithographic steps. It should be noted that the modification of the electron beam technique of domain formation by deposition of an artificial dielectric layer with a high concentration of charge traps at the polar surface allows to significantly improve the quality of the structures created by this method and it is the only possibility of stripe PDS creation at the polar cuts .
Practical significance is associated with the fact that the obtained results will allow us to optimize the technique of PDS creation in ferroelectric crystals and to create new types of non-linear optical and electro-optical devices. At the same time, after further improvement the technology can be used for mass-production using the electron beam lithographers, which significantly accelerates the technological process and will increase the production volumes.
The following set of the techniques will be used: modern methods for sample preparation, dielectric and conductive coatings with controlled thickness, cutting, grinding and polishing of the crystals to optical quality with high precision; the irradiation of the crystals in a scanning electron microscope (SEM) with control of irradiation parameters by electron-beam lithography system; heating and cooling of crystals in vacuum conditions in the SEM chamber; visualization of domain configurations by non-destructive methods of piezoresponse force microscopy and scanning electron microscopy with high spatial resolution; non-destructive method of the visualization of domain configurations in the bulk by the confocal Raman microscopy; the method of the second harmonic generation with spatial scanning to estimate the spatial distribution of efficiency of the laser radiation frequency conversion. The screening of the depolarizing field will be taken into account in describing the evolution of the domain structure in spatially inhomogeneous external fields. The original kinetic approach will be used to describe the features of the evolution of the micro- and nanodomain structures. Thus, the experimental methods and approaches proposed in this project complement each other. That makes it possible to study and obtain reliable results, which will have scientific and practical significance.