E. A. Mingaliev

Formation of the domain structure in CLN under the pyroelectric field induced by pulse infrared laser heating

The evolution of the self-assembled quasi-regular micro- and nanodomain structures after pulse infrared laser irradiation in congruent lithium niobate crystal was studied by in situ optical observation. Several scenarios of domain kinetics represented covering of the irradiated zone by nets of the separated domain chains and rays have been revealed. The time dependence of the total domain length was analyzed in terms of modified Kolmogorov-Avrami theory. The domain structure evolution was attributed to the action of pyroelectric field appeared during cooling. The time dependence of the spatial distribution of the pyroelectric field during pulse laser heating and subsequent cooling was calculated by finite element method. The results of computer simulation allowed us to explain the experimental results and can be used for creation of tailored domain structures thus opening the new abilities of the submicron-scale domain engineering in ferroelectrics.

Micro- and Nanodomain Structures Produced by Pulse Laser Heating in Congruent Lithium Tantalate

Formation of the micro- and nanodomain structures under the action of pyroelectric field induced by pulse IR laser heating was studied in congruent lithium tantalate. Two types of the self-organized domain structures were found. The three-dimensional maze-type structure with average period about 100 nm appeared in the central part of the irradiated zone heated above Tc. The self-similar structure of oriented domain rays with nanoscale width formed at the edge of the irradiated zone. The obtained increase of the average distance between the nanodomain rays for irradiation at the elevated temperatures was attributed to the decrease of the pyroelectric field.

Visualization of nanodomain structures in lithium niobate and lithium tantalate crystals by scanning electron microscopy

ABSTRACT Imaging of ferroelectric domains using scanning electron microscopy is challenging as ferroelectrics are usually highly insulating. However, micro and nanodomain patterns can be directly visualized in secondary electrons using proper parameters. Low accelerating voltage or local charge compensation allows visualizing isolated domains with sizes above 100 nm without any sample preparation. Nanodomain patterns can be visualized with resolution about 3 nm after proper preparation of the sample surface: controlled chemical etching to obtain nanoscale surface relief and subsequent covering of the crystal surface by conductive film. Features of visualization of various nanodomain structures by scanning electron microscopy are considered.

Generation of Picoliter Droplets by Pyroelectrodynamic Effect

The droplet generation under the action of the pyroelectric field created by uniform heating or cooling of the monodomain lithium tantalate plate was studied. The droplets of dielectric and conductive liquid with the volume below picoliter have been deposited on glass substrate with good reproducibility. It was shown that the drying of the dispensed colloid droplets allowed producing the uniform circular and ring-like micron-size patterns of Ag nanoparticles on the substrate. The numerical simulation of attractive force induced by pyroelectric field which is applied to the drop allowed us to explain the obtained results.

Coffee Ring Effect During Drying of Colloid Drop: Experiment and Computer Simulation

Formation of the ring-like patterns of silver nanoparticles (NPs) during drying of colloid drop caused by coffee ring effect has been studied experimentally and by computer simulation. The drop shape evolution during jump-like motion of its contact line was in situ observed. Two interleaved stages of the drop shape evolution were separated for computer simulation. The odd stages represent decreasing of drop height at constant base radius and the even stages – the fast shift of the contact line at the constant volume. The proposed model allows extracting the parameters characterizing formation of NPs pattern during drying of colloid drop.

Investigation of domain kinetics in congruent lithium niobate modified by proton exchange

ABSTRACT The domain structure evolution has been studied in congruent lithium niobate crystals with surface layers modified by three different proton exchange techniques. The significant decrease of the nucleation threshold field and qualitative change of domain rays nucleation and growth have been revealed. The formation of a broad domain boundary and dendrite domain structure as a result of nanodomains merging in front of the moving rays has been demonstrated. The obtained effects have been attributed to features of the domain kinetics induced by built-in electric field and retardation of the bulk screening of depolarization field.

Hysteresis-free high-temperature precise bimorph actuators produced by direct bonding of lithium niobate wafers

The current paper presents a piezoelectric bimorph actuator produced by direct bonding of lithium niobate wafers with the mirrored Y and Z axes. Direct bonding technology allowed to fabricate bidomain plate with precise positioning of ideally flat domain boundary. By optimizing the cutting angle (128° Y-cut), the piezoelectric constant became as large as 27.3 pC/N. Investigation of voltage dependence of bending displacement confirmed that bimorph actuator has excellent linearity and hysteresis-free. Decrease of the applied voltage down to mV range showed the perfect linearity up to the sub-nm deflection amplitude. The frequency and temperature dependences of electromechanical transmission coefficient in wide temperature range (from 300 to 900 K) were investigated.

Deposition of droplets by pyroelectric field created by lithium tantalate with tailored domain structure

ABSTRACT A new concept of pyroelectric electrohydrodynamic system for deposition of the micron size droplets at the predetermined position on the substrate with high accuracy using pyroelectric field created by lithium tantalate with tailored domain structure has been proposed. The optimal geometry of the domain pattern has been obtained by computer simulation of the spatial distribution of surface pressure acting on liquid/vapor interface induced by pyroelectric field. The proposed technique was applied to dispense the silicon oil and the water solution of amino acid glycine.

Formation of self-organized nanodomain structures in lithium niobate after pulsed infrared laser heating

The formation of nanodomain structures in single crystals of congruent lithium niobate during cooling after pulsed infrared laser heating was studied. In situ visualization of the evolution of the domain structure allowed us to reveal the appearance of isolated domains at the edges of the irradiated zone and subsequent growth of the domain rays toward its center. The obtained results attract essential interest for creation of the periodic domain structure.

Surface-Enhanced Raman Scattering Using Silver Nanoparticles Produced by Laser Ablation in Liquid

The active substrates with rings of silver nanoparticles arising by drying of sessile colloid drops were used for realization of the surface-enhanced Raman scattering. The colloids have been produced by laser ablation in water using pulse Yb fiber laser. The droplets with diameter down to 10 μm were dispensed by electrohydrodynamic technique by means of pyroelectric field produced by lithium tantalate plate. The optimal spatial distribution of hotspots was obtained for substrate covered by the micron-size rings of silver nanoparticles. The method was applied for various organic molecules rhodamine 6G, thymine, and RNA with enhancement factor up to 105.