Formation of dendrite domain structures in stoichiometric lithium niobate at elevated temperatures

Formation of the dendrite-type self-organized domain structures during polarization reversal at elevated temperatures (above 230°C) has been revealed and studied in stoichiometric lithium niobate LiNbO3 single crystals. Optical, confocal Raman, scanning electron, and piezoelectric force microscopy have been used for domain visualization. It has been shown experimentally that formation of the dendrite-like structures has been attributed to correlated nucleation caused by a field distribution in the vicinity of the charged domain walls. © 2012 American Institute of Physics

In situ imaging of domain structure evolution in labgeo5 single crystals

LaBGeO5 (LBGO) crystals are unique ferroelectric materials for manufacturing highly efficient UV laser sources based on frequency conversion. This is due to their low cut-off wavelength, high nonlinear-optical coefficients, and non-hygroscopicity. Periodical poling requires a deep study of domain kinetics in these crystals. Domain imaging by Cherenkov second harmonic generation microscopy was used to reveal the main processes of domain structure evolution: (1) growth and merging of isolated domains, (2) growth of stripe domains formed on the artificial linear surface defects, and (3) domain shrinkage. In a low field, growth of triangular domains and fast shape recovery after merging were observed, while in a high field, the circular domains grew independently after merging. The revealed essential wall motion anisotropy decreased with the field. The anisotropy led to significant shape transformations during domain shrinkage in low field. The formation of short-lived triangular domains rotated by 180 degrees with respect to the growing isolated domains was observed. The obtained results were explained within the kinetic approach to domain structure evolution based on the analogy between the growth of crystals and ferroelectric domains, taking into account the gradual transition from determined nucleation in low field to the stochastic one in high field. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 19-12-00210Funding: This research was funded by the Russian Science Foundation, grant number 19-12-00210

Sizes and fluorescence of cadmium sulfide quantum dots

Cadmium sulfide quantum dots have been synthesized by wet chemical deposition from an aqueous solution. The sizes of the quantum dots determined by dynamic light scattering directly in the colloidal solution and by intermittent-contact atomic force microscopy in the dry sediment agree with each other. It has been found that splitting of the fluorescence peaks of the quantum dots can be affected by the disorder of the atomic structure of cadmium sulfide quantum dots. © 2013 Pleiades Publishing, Ltd

Self-organized growth of dendrite domains in lithium niobate and lithium tantalate single crystals

The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was used. The research was made possible by Russian Science Foundation (Project №14-12-00826)

As-Grown Domain Structure in Calcium Orthovanadate Crystals

An as-grown domain structure in nominally pure and Mn-doped calcium orthovanadate (CVO) crystals was studied by several methods of domain imaging: optical microscopy, piezoelectric force microscopy, and Cherenkov-type second harmonic generation. The combination of imaging methods provided an opportunity for comprehensive study of the domain structure on the polar surface and in the bulk of the samples. It was shown that, in nominally pure CVO crystals, an irregular 3D maze of rounded domains, with charged walls, essentially tilted from the polar direction, was present. It was proposed that the domain structure was formed just below the phase transition temperature and persisted during subsequent cooling. Such behavior is due to effective bulk screening of the depolarization field and a low value of the pyroelectric field which appears during cooling. The revealed formation of triangular domains and flat fragments of domain walls in Mn-doped CVO was attributed to polarization reversal under the action of the polar component of the pyroelectric field, above the threshold value for domain switching. This fact represents the first observation of the domain switching in CVO crystals. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research was funded by the Russian Foundation for Basic Research, grant number 20-02-00588-a, and the Ministry of Science and Higher Education of the Russian Federation, grant numbers 075-15-2021-677 and FEUZ-2020-0054

Charged domain walls in lithium tantalate with compositional gradients produced by partial VTE process

The morphology of a single charged domain wall, appeared under the action of composition gradients produced by partial VTE procedure by Cherenkov-type second harmonic generation microscopy, was observed in detail. The width of the charged domain wall was estimated as 70 μm. Non-through and through narrow domains, grown from the charged domain wall, were revealed. The maximum length of non-through domains with submicron diameter was about 100 μm. The growth of narrow domains from the charged domain wall was demonstrated and attributed to the action of pyroelectric field. The widening of domains occurred after achieving the polar surface. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 19-12-00210The equipment of Ural Centre for Shared Use “Modern Nanotechnology” Ural Federal University was used. The research was made possible by Russian Science Foundation (project № 19-12-00210)

Electron beam poling of [001]c-poled PMN-39PT single crystal

The equipment of the Ural Center for Shared Use “Modern Nanotechnology” UrFU has been used. The research was made possible in part by Government of the Russian Federation (Act 211, Agreement 02.180 A03.21.0006) and RFBR (grant 17-52-80116-BRICS_a)

Charged domain walls in lithium tantalate with compositional gradients produced by VTE process

The equipment of Ural Center for Shared Use “Modern Nanotechnology” Ural Federal University was used. The research was made possible by Russian Science Foundation (Project № 19-12-00210)