A. I. Lobov

Rearrangement of ferroelectric domain structure induced by chemical etching

The rearrangement of the domain structure induced by chemical etching has been observed in periodically poled MgO-doped stoichiometric lithium tantalate single crystals. Topographic and piezoresponse scanning probe microscopy have been used for measuring the etching relief height and domain wall position after etching. The considerable shift of the domain wall during etching by pure hydrofluoric acid has been revealed by analysis of the experimental data. We have found that the wall motion proceeded after the termination of the etching procedure. We have shown that the whole consequence of the domain wall positions during etching is recorded in the etching relief height and can be extracted with high spatial and temporal resolution.

Formation of Self-Similar Surface Nano-Domain Structures in Lithium Niobate Under Highly Nonequilibrium Conditions

Formation of the nanoscale domain structure in the surface layer as a result of pulsed UV laser irradiation has been studied experimentally in congruent single crystalline lithium niobate LiNbO3. The self-assembled structures have been classified and statistically analyzed. The structure is formed by growth, turning, and branching of domain rays strictly oriented along three Y+ directions. High-resolution microscopy shows that the rays represent the chains of individual needle-like nano-domains. The results of computer simulation of the domain structure formation using experimentally revealed rules are in good agreement with the experimental ones.

Field induced evolution of regular and random 2D domain structures and shape of isolated domains in LiNbO3 and LiTaO3

The shapes of isolated domains produced by application of the uniform external electric field in different experimental conditions were investigated experimentally in single crystalline lithium niobate LiNbO 3 and lithium tantalate LiTaO 3 . The study of the domain kinetics by computer simulation and experimentally by polarization reversal of the model structure using two-dimensional regular electrode pattern confirms applicability of the kinetic approach to explanation of the experimentally observed evolution of the domain shape and geometry of the domain structure. It has been shown that the fast domain walls strictly oriented along X directions appear after domain merging.

In situ investigation of formation of self-assembled nanodomain structure in lithium niobate after pulse laser irradiation

The evolution of the self-assembled quasi-regular micro- and nanodomain structures after pulse infrared laser irradiation was studied by in situ optical observation. The average periods of the structures are much less than the sizes of the laser spots. The polarization reversal occurs through covering of the whole irradiated area by the nets of the spatially separated nanodomain chains and microdomain rays—“hatching effect.” The main stages of the anisotropic nanodomain kinetics: nucleation, growth, and branching, have been singled out. The observed abnormal domain kinetics was attributed to the action of the pyroelectric field arising during cooling after laser heating.

Shape of isolated domains in lithium tantalate single crystals at elevated temperatures

The shape of isolated domains has been investigated in congruent lithium tantalate (CLT) single crystals at elevated temperatures and analyzed in terms of kinetic approach. The obtained temperature dependence of the growing domain shape in CLT including circular shape at temperatures above 190 °C has been attributed to increase of relative input of isotropic ionic conductivity. The observed nonstop wall motion and independent domain growth after merging in CLT as opposed to stoichiometric lithium tantalate have been attributed to difference in wall orientation. The computer simulation has confirmed applicability of the kinetic approach to the domain shape explanation.

Formation of Nano-Scale Domain Structures in Lithium Niobate Using High-Intensity Laser Irradiation

The polarization reversal process under pulsed laser irradiation without application of electric field was investigated in single crystalline congruent and MgO doped lithium niobate LiNbO 3 . The nano-domain structures obtained in different experimental conditions were statistically analyzed and characterized in terms of domain growth anisotropy.

Investigation of Jerky Domain Wall Motion in Lithium Niobate

Jerky domain wall motion during merging of neighboring domains in lithium niobate single crystals was studied in details by using synchronized in-situ optical visualization and recording of switching current shape. Several scenarios of domain structure transformation were revealed and classified. It has been shown that predetermined nucleation and layer-by-layer mechanism are main reasons for observed jerky domain wall motion. On the basis of the analysis of the current pulse shape the step growth velocity was estimated to be about 1 m/s. This value is several orders of magnitude higher than the averaged visible domain wall velocity in lithium niobate.

Discrete Switching by Growth of Nano-Scale Domain Rays Under Highly-Nonequilibrium Conditions in Lithium Niobate Single Crystals

The formation of nano-domain structure as a result of pulsed laser irradiation of lithium niobate single crystals has been studied experimentally applying optical and atomic force microscopy for visualization of nano-domain patterns. The observed growth of oriented nano-domain rays was considered as a manifestation of polarization reversal in highly nonequilibrium switching conditions. The results of computer simulation of nano-domain kinetics under the action of pyroelectric field during cooling after pulsed heating were used for explanation of the studied peculiarities of nano-domain kinetics. The screening effect retardation was taken into account. The main predictions of the simulations were confirmed experimentally.

Shape Evolution of Isolated Micro-Domains in Lithium Niobate

The varieties of domain shapes produced in single crystals of lithium niobate LiNbO 3 family by application of the uniform electric field have been revealed. The crucial role of predetermined nucleation effect representing the step generation at vertices of polygon domain and step growth in three Y directions was discussed. We put emphasis on formation of unusual domain shapes created by switching in non-equilibrium conditions arisen due to retardation of the screening of depolarization field. Formation of oriented fingers and dendrite self-assembled domain structures during switching with artificial surface dielectric layer and during spontaneous backswitching was considered.

Self-similar surface nanodomain structures induced by laser irradiation in lithium niobate

Self-similar surface structures composed of nanodomain rays, which are formed in congruent lithium niobate single crystals under pulsed laser irradiation, are investigated. The computer simulation of the formation of the domain structure is performed using the experimentally revealed rules of ray growth. It is demonstrated that the domain structures formed are fractal objects with a limited range of scaling.