We review the most interesting aspects of the domain structure kinetics in ferroelectrics important for "domain engineering" and discuss them in the framework of a unified nucleation approach. In our approach the nucleation rate is determined by the local value of electric field produced not only by bound charges and voltage applied to the electrodes, but also by screening charges. As a result, any kinetically produced domain pattern, even being far from the equilibrium, can be stabilized by bulk screening. The domain evolution represents a self-organizing process in which the screening of polarization plays the role of feedback. The general approach was applied for the description of the domain kinetics in lithium niobate and lithium tantalate as the most versatile materials for applications. The revealed original scenarios of the domain structure evolution are attributed to the retardation of the screening processes. The decisive role of screening effectiveness for shapes of individual domains and scenarios of the sideways domain wall motion is demonstrated both experimentally and by computer simulation. The possibility to produce a self-assembled nano-scale domain structures with controlled periods has been shown. C 2006 Springer Science + Business Media, Inc.
IntroductionA new branch of science and technology directed to the creation of periodic and quasi-periodic domain structures with desired parameters in commercially available ferroelectrics denoted as "domain engineering" is rapidly developing nowadays. Domain engineering in ferroelectric crystals, such as lithium niobate LiNbO 3 (LN) and lithium tantalate LiTaO 3 (LT), has revolutionized their use in nonlinear optical applications [1,2]. The performance of LN and LT as an electro-optic, photorefractive, piezoelectric, and nonlinear optical crystals, make them useful for many different applications. It has been shown that LN and LT with periodical 1D-and 2D-domain structures possessing an efficient quasi-phase-matching open up a wide range of possibilities for bulk and waveguide nonlinear optical devices [2][3][4]. During ten years after the first electrical poling of bulk LN samples [5], research on periodically poled LN and LT is under intense interest around the world resulting in production of photonic devices. Breaking the micron-period barrier for periodical domain patterning in LN and LT is very desirable for several new electrooptic applications such as tunable cavity mirrors, which need a periodicity of about 350 nm. The most efficient