Tilt control of the charged domain walls in lithium niobate

Abstract

Precise control of the domain structure in ferroelectric single crystals is one of the most important and challenging tasks in physics of ferroelectrics. So far, main part of investigations in this area was aimed at realization of high efficiency nonlinear optical interactions, such as second harmonic generation (SHG) and optical parametric oscillation. These applications require precise spatial variation of the spontaneous polarization, which distribution within the crystal is determined by the positions and orientations of the domain walls (DWs). Recently, the scientific attention has turned from the domains to the DWs themselves: these movable unit-cell-thick interfaces were proposed as the building blocks for reconfigurable nanoelectronics devices, because their properties can differ drastically from the bulk parent material [1, 2]. In particular, it has been shown that conductivity of the charged domain walls (CDWs) in ferroelectrics is many orders of magnitude higher, than that in the single domain state [3]. The utilization of the CDW as nanoelectronics devices requires three technological aspects to be developed: (1) controllable creation, (2) geometry tuning, and (3) removal. We present the experimental study of the CDW formation in congruent lithium niobate single crystals during polarization reversal using liquid and solid-state electrodes, as well as their combination [4]. It was shown that material of the electrode applied to the Z-polar surface is crucial. It was shown that CDW can be formed by two alternative procedures: (1) by forward switching for liquid electrode at Z+ polar surface and solid electrodeat Zone , (2) by backward switching for solid electrode at Z+ polar surface and liquid electrode at Zone. The obtained domain structure was investigated in the bulk of the crystal using scanning Cherenkov-type SHG microscopy [5]. For both used procedures the CDWs were formed when domains grew from Z+ polar surface covered by solid or liquid electrode towards Z-surface covered by solid electrode. Thus, existence of the solid electrode on Z-surface is the necessary condition for CDW formation. The created CDW can be transformed to almost neutral domain wall by application of the field pulse of the reverse polarity for both procedures. As a result, the tilt of the formed CDW can be tuned reversibly in the range from 0.2 to 1.2 degrees resulting in change between almost isolated and highly conductive states. When the tilt exceeded 1.2 degrees the CDW became jugged due to formation of additional spikes. For the second procedure the unusual partial backward switching during forward polarization reversal was revealed. Moreover, we have demonstrated that the created CDW can be used as a nanoelectronics channel for local electrolysis opening the additional possibilities for the ferroelectric lithography. The equipment of the Ural Center for Shared Use "Modern nanotechnology" Ural Federal University was used. The research was made possible in part by RFBR (grant 18-32-00641_mol_a).

Tailoring of stable induced domains near a charged domain wall in lithium niobate by probe microscopy

“…Ferroelectric lithium niobate (LiNbO 3 ) crystals with an engineered domain structure have a number of applications in optical systems for generation of multiple laser radiation harmonics, acoustooptics, precision actuators, vibration and magnetic field sensors, including those for high-temperature applications, and prospectively, in non-volatile com-puter memory [1][2][3][4][5][6][7][8][9][10][11][12]. Despite the availability of proven technologies of growth of the crystals with required ferroelectric domain structures and devices on their basis, researchers draw much attention to the fundamental properties of domain structures, their technologies, formation kinetics and description at micro-and macroscopic levels [13][14][15][16][17].…”

Forward growth of ferroelectric domains with charged domain walls. Local switching on non-polar cuts

“…However, it is known nowadays that this postulate is wrong and the metastable domain structures with CDW are extensively studied in various ferroelectrics both experimentally and theoretically. [38][39][40][41] The formation of the nanodomain with in-plane polarization in non-polar-cut samples of uniaxial ferroelectrics LN and lithium tantalate by SPM was theoretically considered by Pertsev andKholkin. 42 The calculated equilibrium sizes and a wedge-like shape of the subsurface nanodomains oriented along the polar axis were attributed to a spatial distribution of the polar component of the electric field.…”

Engineering Individual Oxygen Vacancies: Domain-Wall Conductivity and Controllable Topological Solitons

“…Substantial effort has been given though to domain-wall conductivity in large-bandgap ferroelectrics, vastly because domain walls are movable by will with external electric fields, giving rise to miniaturized memristive cells. 17 − 19 While the success of presenting domain-wall conductivity in traditional perovskite ferroelectrics, such as BaTiO 3 20 and Pb(Zr 0.2 Ti 0.8 )O 3 , has remained limited, 21 − 23 attention has been given mainly to BiFeO 3 , 24 − 27 ErMnO 3 , 28 , 29 and LiNbO 3 , 30 − 32 which show high and reproducible conductivity.…”