Static conductivity of charged domain walls in uniaxial ferroelectric semiconductors

Abstract

Using Landau-Ginzburg-Devonshire theory we calculated numerically the static conductivity of charged domain walls with different incline angle with respect to spontaneous polarization vector in the uniaxial ferroelectrics-semiconductors of n-type. We used the effective mass approximation for the electron and holes density of states, which is valid at arbitrary distance from the domain wall.Due to the electrons accumulation, the static conductivity drastically increases at the inclined head-to-head wall by 1 order of magnitude for small incline angles θ~π/40 by up 3 orders of magnitude for the perpendicular domain wall (θ=π/2).There are space charge regions around the charged domain walls, but the quantitative characteristics of the regions (width and distribution of the carriers) appeared very different for the tail-to-tail and head-to-head walls in the considered donor doped ferroelectric semiconductor.The head-to-head wall is surrounded by the space charge layer with accumulated electrons and depleted donors of the same thickness (~40−100 correlation lengths). The tail-to-tail wall is surrounded by the thin space charge layer with accumulated holes of thickness ~5-10 correlation lengths and thick layer with accumulated donors of thickness ~100−200 correlation lengths, as well as the layer with depleted by electrons of thickness ~100−200 correlation lengths.* Corresponding author, e-mail: morozo@i.com.ua † Corresponding author, e-mail: vladimir.shur@usu.ru 2 The conductivity across the tail-to-tail wall is at least an order of magnitude smaller than the one of the head-to-head wall due to the low mobility of holes, which are improper carries.The results are in qualitative agreement with recent experimental data for LiNbO 3 doped with MgO.

Polar-Graded Multiferroic SrMnO3 Thin Films

“…The presence of extended domain walls in ferroelectric materials has been a matter of intense debate. Recent works reported domain-wall thickness differences between charged an uncharged 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 16 ferroelectric-180º and ferroelastic-90º walls quantitatively measured at the atomic scale in epitaxial PbTiO 3 thin films 41,42 , in which the strong depolarizing field of the head-to-head dipoles is stabilized by distributing the polarization charge over an extended thickness 41,45 . However, in multiferroic materials domain walls are generally thicker than in normal ferroelectrics which may depend on the degree of coupling and correlation length between the two ferroic orders 11,[46][47][48] .…”

Regular nanodomain vertex arrays in BiFeO3single crystals

“…15 When judging the properties of domains and domain walls in multiferroic materials, the orientation (habit plane) of the domain wall in relation to the polarization direction has to be carefully considered. 16,17 This is the reason why we not only report on the observation of a new type of nanodomain in BiFeO 3 single crystals by transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM), the shape and arrangement of which correspond to a linear arrangement of vertices, but also strive to analyze the geometry and orientation of the domain walls in some detail. From the observations, a reasonable domain model is derived.…”

Polarization control at spin-driven ferroelectric domain walls

“…In particular, the polarity mismatch at charged walls leads to characteristics that clearly distinguish them from the interior of the domains they separate [1][2][3][4] . Such ferroelectric domain walls can behave as a two-dimensional insulator 5 , become metallic 6,7 , show orientation-dependent electrical conductance [8][9][10] or anisotropic magnetoresistance 11 , even when the bulk material has none of these properties. Exotic domain-wall phenomena are observed in archetypal ferroelectrics, such as BaTiO 3 (refs 12,13), PbZr 0.2 Ti 0.8 O 3 (refs 7,14,15) and LiNbO 3 (ref.…”