L. V. Gimadeeva

Periodic domain patterning by electron beam of proton exchanged waveguides in lithium niobate

Formation of domain structure by electron beam irradiation in congruent lithium niobate covered by surface dielectric layer with planar and channel waveguides produced by Soft Proton Exchange (SPE) process has been studied. Formation of domains with arbitrary shapes as a result of discrete switching has been revealed. The fact was attributed to ineffective screening of depolarization field in the crystals with a surface layer modified by SPE process. The dependences of the domain sizes on the dose and the distance between irradiated areas have been revealed. Finally, we have demonstrated that electron beam irradiation of lithium niobate crystals with surface resist layer can produce high quality periodical domain patterns after channel waveguide fabrication. Second harmonic generation with normalized nonlinear conversion efficiency up to 48%/(W cm2) has been achieved in such waveguides.

Influence of the artificial surface dielectric layer on domain patterning by ion beam in MgO-doped lithium niobate single crystals

We experimentally compared the shapes and sizes of isolated domains created by the focused ion beam irradiation in the lithium niobate crystals doped by MgO with polar surface covered by dielectric (resist) layer and those with free surface. We attributed the larger sizes of isolated domains in the samples covered by the resist layer to ion localization in the resist. We revealed a change in the domain shape as a function of increasing dose and explained it in terms of kinetic approach taking into account the modification of the surface layers by ion irradiation. We applied the obtained knowledge for 1D and 2D periodical poling using ion beam. Finally, we created the 2D square 1-μm-period array of isolated domains with radius about 300 nm and maximal depth of all domains in the array up to 100 μm as well as the 1D pattern of through stripe domains with 2-μm-period in 1-mm-thick wafer.

Growth of isolated domains induced by focused ion beam irradiation in congruent lithium niobate

ABSTRACT Formation of isolated domains induced by i-beam irradiation in single crystals of congruent lithium niobate with polar surface covered by uniform resist layer was studied. The change of domain shape with dose increase was attributed to gradual penetration of charge through the resist layer caused by i-beam milling. The appearance of the dendrite structures was attributed to formation of the surface dielectric gap due to out-diffusion of oxygen to electrode. We applied the obtained knowledge for creation of the 1-µm-period 2D square arrays of isolated domains with minimal radius about 300 nm and the 1-µm-period 1D pattern of stripe domains.

Local switching in SBN:Ni single crystals with various initial domain states

ABSTRACT We present the results of experimental study of the local switching in single crystals of relaxor ferroelectric Ni-doped strontium barium niobate with various initial domain states using conductive tip of scanning probe microscope. We investigated the domain growth in as-grown domain structure and initial domain states created by: (i) scanning by biased tip, (ii) in-field cooling, and (iii) scanning by electron beam. The dependences of effective domain radius on the voltage and pulse duration were derived. The shape factor, domain wall mobility, and start voltage were revealed. The obtained results can be used for the domain engineering in ferroelectrics.

Domain wall shape instability in congruent lithium tantalate during switching by ion beam

ABSTRACT The formation of domain arrays and domain wall shape instability induced by ion beam irradiation have been studied in congruent lithium tantalate crystal covered by dielectric layer. The dependences of domain radii on exposure dose and array period were obtained. The domain wall shape instability effect (appearance of periodical oriented fingers) for doses above 20 pC was revealed. It was shown that dose increase led to increase of total length of the domain wall with fingers, while the finger number remained approximately constant. The observed results were explained by the kinetic approach based on analogy with first order phase transitions.

Domain structure evolution in relaxor PLZT 8/65/35 ceramics after chemical etching and electron beam irradiation

ABSTRACT Domain structure and its evolution on the surface of PLZT 8/65/35 ceramics after selective chemical etching and e-beam irradiation was studied. It is shown that the initial mixture of the nanoscale fractal-type 3D maze (fractal dimension 2.8) and micron-size domains turned into lamellar domains with periods ranging from 100 to 800 nm as a result of such procedures. The observed etch-induced change of the domain structure was attributed to the action of the depolarization field after partial removing the screening charges. The dependence of the switched domain area on irradiation time (dose) was measured in e-beam irradiated samples.