Polar Discontinuity Research Articles

Rapid polarization mapping in ferroelectrics using Fourier masking.

Ferroelectric materials, and more specifically ferroelectric domain walls (DWs) have become an area of intense research in recent years. Novel physical phenomena have been discovered at these nanoscale topological polarization discontinuities by mapping out the polarization in each atomic unit cell around the DW in a scanning transmission electron microscope (STEM). However, identifying these features requires an understanding of the polarization in the overall domain structure of the TEM sample, which is often a time-consuming process. Here, a fast method of polarization mapping in the TEM is presented, which can be applied to a range of ferroelectric materials. Due to the coupling of polarization to spontaneous strain, we can isolate different strain states and demonstrate the fast mapping of the domain structure in ferroelectric lead titanate (PTO). The method only requires a high-resolution TEM or STEM image and is less sensitive to zone axis or local strain effects, which may affect other techniques. Thus, it is easily applicable to in-situ experiments. The complimentary benefits of Fourier masking with more advanced mapping strategies and its application to other materials are discussed. These results imply that Fourier masked polarization mapping will be a useful tool for electron microscopists in streamlining their analysis of ferroelectric TEM samples. LAY DESCRIPTION: This paper addresses a problem that often occurs when looking at a ferroelectric material in the Transmission Electron Microscope (TEM). Ferroelectric samples are interesting because they form tiny areas inside themselves with arrow of charge in each one. The thinner the sample, the smaller these regions, called "domains" become. These arrows of charge point in different directions in each domain of the sample. The boundary where these domains meet have interesting properties to study in a TEM but it's important to figure out which way the arrows point in the domains around the boundary. What causes the arrows in the different domains is tiny shifts of different atoms in unit cell away from their neutral position, usually because they're being squeezed by pressure from the domains nearby. The problem is that these tiny atoms moving are difficult to measure and see where the charged arrow is pointing, often it's hard to know how many different domains are even in the sample and where they begin. This paper discusses a method called "Fourier masking" to quickly see what's going on in the overall TEM sample, where the domains are and roughly where the arrows point. It does this by looking at the spacings of the atoms from a magnification where you can just about see the lines of atoms. In lead titanate the unit cell is a rectangle and the arrow always points in line with the long side of the rectangle. The Fourier masking lets you see which direction the long side of the rectangular unit cell is pointing in different parts of your TEM image. The big advantage is that it takes about two minutes to do and uses software that almost every TEM already has. That lets the TEM user quickly know where the domains are in their TEM samples and roughly which way the arrows of charge are pointing. Then they can choose the most interesting features focus on for higher resolution analysis.

Electrostatics liberating restrictions on ferroelectric by unification of polar discontinuity e–h+ layers and criteria of intrinsicality

Electron e– and hole h+ layers at polar discontinuities as a thermodynamically stable state previously predicted are recently shown by many experiments. We discuss that these layers including those at SrTiO3/LaAlO3 support our previous prediction of the substantially reduced electrostatic restrictions on ferroelectricity such as size effect and domains when the origins of these conductions are intrinsic. For this, the criteria of the intrinsicality of these layers, i.e., not due to conventional mechanisms such as defects and adsorbates, are presented. In addition, we discuss that this reduction of the electrostatic restriction is the same as recently proposed hyperferroelectricity and show that hyperferroelectricity is a universal properties of general ferroelectric.

Photoresponsive properties at (0 0 1), (1 1 1) and (1 1 0) LaAlO3/SrTiO3 interfaces

We report the photoresponsive characteristics of (0 0 1), (1 1 0), and (1 1 1) LaAlO3/SrTiO3 heterointerfaces deposited at different oxygen pressures using a 360 nm light. The results show that LaAlO3/SrTiO3 interfaces with less oxygen vacancies exhibit a larger resistance change when illuminated by light and a slower recovery process when light is off. In addition, the (1 1 0) LaAlO3/SrTiO3 heterointerfaces present the smallest photoinduced change and residual photoinduced change in the resistance, which are related to the negligible polarization discontinuity at the interfaces. Our results provide a deeper insight into the photoinduced properties in the 2D electron gas system, paving the way for the design of oxide optoelectronic devices.

Optical second harmonic generation from LaAlO3/SrTiO3 interfaces with different in-plane anisotropies

Oxide growth with semiconductor-like accuracy allows the fabrication of atomically precise thin films and interfaces displaying a wide range of phases and functionalities that are absent in the corresponding oxide bulk materials. Among the other properties it was found that a two-dimensional electronic gas is formed under some circumstances at the LaAlO3/SrTiO3(0 0 1) interface separating two typical insulating perovskite crystals. The origin of this conducting state has been discussed at length, since different doping mechanisms can act in these material systems. Many experimental results point to the so-called polar catastrophe scenario as the principal mechanism driving the formation of the two-dimensional electronic gas. According to this mechanism, the existence of an interfacial polar discontinuity is the key ingredient to drive an electronic reconstruction at the LaAlO3/SrTiO3(0 0 1) interface and the consequent formation of a two-dimensional electron gas. This simple picture has been often questioned by the existence of material systems whose interface are predicted being non-polar according to the simplistic ‘ionic’ limit but that display an electrical behavior analogous to that of LaAlO3/SrTiO3(0 0 1) interfaces. This is the case of the LaAlO3/SrTiO3(1 1 0), i.e., a LaAlO3/SrTiO3 interface with a different in-plane orientation. It is evident that to solve such kind of controversies a detailed investigation of the polar or non-polar state of these interfaces is needed, although this is not simple for the lack of experimental tools that are specifically sensitive to interfacial polarity. Here we apply Optical Second Harmonic Generation to investigate LaAlO3/SrTiO3 interfaces with different in-plane orientations to bridge this gap. By comparing our results with recent theoretical findings, we will arrive to the conclusion that the real LaAlO3/SrTiO3(1 1 0) interface is strongly polar.

Giant polarization charge density at lattice-matched GaN/ScN interfaces

Rock-salt ScN is a semiconductor with a small lattice mismatch to wurtzite GaN. Within the modern theory of polarization, ScN has a nonvanishing formal polarization along the [111] direction. As a result, we demonstrate that an interface between (0001) GaN and (111) ScN exhibits a large polarization discontinuity of −1.358 Cm−2. Interfaces between ScN and wurtzite III-nitrides will exhibit a high-density electron gas at the (0001¯) GaN interface or a hole gas at the (0001) GaN interface, with carrier concentrations up to 8.5×1014 cm−2. The large polarization difference and small strain make ScN a desirable choice for polarization-enhanced tunnel junctions within the III-nitride materials system. The large sheet carrier densities may also be useful for contacts or current spreading layers.

Review—Defect-Tolerant Luminescent Properties of Low InN Mole Fraction InxGa1-xN Quantum Wells under the Presence of Polarization Fields

Different from the case of GaN or AlGaN alloys, the near-band-edge (NBE) emission of quantum wells (QWs) and even epilayers of InxGa1-xN alloys of low InN mole fractions (x) exhibits high quantum-efficiency (QE) against the presence of threading dislocations (TDs) as high as 109 cm−2. Accordingly InxGa1-xN alloys are exclusively used as an active region of green to ultraviolet light-emitting diodes (LEDs) and laser diodes, as well as the heart of white LEDs. Here, current understandings on the emission mechanisms of InxGa1-xN QWs, especially the defect-tolerant emission probability of localized excitons, are reviewed. There exist three disadvantages in obtaining high QE, namely a high density of TDs that cause the nonradiative recombination, kinetic immiscibility of In-containing alloys that introduces high-concentration Shockley-Read-Hall nonradiative recombination centers (NRCs) consisting of vacancy complexes, and high internal electric-fields across the QWs induced by the polarization discontinuities at heterointerfaces along the c-axis, which decrease the radiative recombination rate. The use of InxGa1-xN alloys of low x overcomes such disadvantages with the aid of In-originated localization effects that prevent excitons from trapping by TDs or NRCs. Simultaneous observation of short diffusion length and sufficiently long nonradiative recombination lifetime at room temperature indicates strong localization of holes or excitons.

Flexoelectric healing of intrinsically more conductive nanochannels in NdNiO3 thin films

Rare-earth nickelates have received great attention owing to the extreme sensitivity of their metal-insulator transition (MIT) and particularly the local defect state under external perturbation. Accordingly, it is critical to effectively control their local defect state to tailor the MIT. However, although macroscopic MIT behavior has been extensively studied, the relationship between the local defect state related to polar discontinuity and MIT has been rarely investigated. Herein, we demonstrate the presence of intrinsic conductive nanochannels due to the Ni deficiency induced by the polar discontinuity and the flexoelectric healing of such nanochannels in NdNiO3 thin films using atomic force microscopy (AFM). The results indicate that the intrinsic conductive nanochannels are likely related to the Ni vacancy. Intriguingly, these conductive nanochannels are effectively removed by the application of mechanical force with the AFM tip, i.e., flexoelectric healing. Our findings suggest that mechanical stimuli can be one of the effective ways for modulating the intrinsic defect state and the corresponding properties at the nanoscale.

An Electronically Driven Improper Ferroelectric: Tungsten Bronzes as Microstructural Analogs for the Hexagonal Manganites.

Since the observation that the properties of ferroic domain walls (DWs) can differ significantly from the bulk materials in which they are formed, it has been realized that domain wall engineering offers exciting new opportunities for nanoelectronics and nanodevice architectures. Here, a novel improper ferroelectric, CsNbW2 O9 , with the hexagonal tungsten bronze structure, is reported. Powder neutron diffraction and symmetry mode analysis indicate that the improper transition (TC = 1100 K) involves unit cell tripling, reminiscent of the hexagonal rare earth manganites. However, in contrast to the manganites, the symmetry breaking in CsNbW2 O9 is electronically driven (i.e., purely displacive) via the second-order Jahn-Teller effect in contrast to the geometrically driven tilt mechanism of the manganites. Nevertheless CsNbW2 O9 displays the same kinds of domain microstructure as those found in the manganites, such as the characteristic six-domain "cloverleaf" vertices and DW sections with polar discontinuities. The discovery of a completely new material system, with domain patterns already known to generate interesting functionality in the manganites, is important for the emerging field of DW nanoelectronics.

Interface-based tuning of Rashba spin-orbit interaction in asymmetric oxide heterostructures with 3d electrons

The Rashba effect plays important roles in emerging quantum materials physics and potential spintronic applications, entailing both the spin orbit interaction (SOI) and broken inversion symmetry. In this work, we devise asymmetric oxide heterostructures of LaAlO3//SrTiO3/LaAlO3 (LAO//STO/LAO) to study the Rashba effect in STO with an initial centrosymmetric structure, and broken inversion symmetry is created by the inequivalent bottom and top interfaces due to their opposite polar discontinuities. Furthermore, we report the observation of a transition from the cubic Rashba effect to the coexistence of linear and cubic Rashba effects in the oxide heterostructures, which is controlled by the filling of Ti orbitals. Such asymmetric oxide heterostructures with initially centrosymmetric materials provide a general strategy for tuning the Rashba SOI in artificial quantum materials.

Polarization discontinuity driven two dimensional electron gas at A2Mo3O8/B2Mo3O8 (A, B: Zn, Mg, Cd) interfaces

We propose a novel heterostructure system consisting of compounds with chemical formula A2Mo3O8 (A, B: Zn, Mg, Cd) that can host a two-dimensional electron/hole gas (2DEG/2DHG). The formation of a 2DEG/2DHG in these heterostructures, which have a low interfacial strain, is driven by a polarization discontinuity at the interface. The sheet carrier densities and charge localization in these heterostructures are comparable to other well-known heterostructures that host 2DEG opening up the possibility of a wide variety of applications.

Elucidating the origins of the two-dimensional electron gas in LaVO3/SrTiO3 interfaces

The influence of growth rate and substrate temperature on the two-dimensional electron gas (2DEG) of LaVO3/SrTiO3 interfaces has been investigated. It is found that both growth rate and substrate temperature can modulate the structural and electrical properties of the LaVO3/SrTiO3 interfaces through oxygen substrate-to-film transfer. When the LaVO3 thin films are deposited at a low substrate temperature and a high growth rate, the LaVO3/SrTiO3 interfaces exhibit weak oxygen substrate-to-film transfer and resultant low density of oxygen vacancies in the SrTiO3 substrate. As a result, the intrinsic effect (polar discontinuity and/or dielectric screening) dominates the interfacial conduction, while the oxygen vacancies play a minor role. In contrast, the oxygen substrate-to-film transfer (oxygen vacancies in the SrTiO3 substrate) can be enhanced (increased) by depositing the LaVO3 thin films at lower growth rates and/or higher substrate temperatures. In this case, the contribution of oxygen vacancies to the interfacial conduction would prevail over the intrinsic effect. Our results elucidate the origins of 2DEG in the LaVO3/SrTiO3 interfaces and may also be important for other SrTiO3-based heterointerfaces.

The diverse electronic properties of C/BN heteronanotubes with polar discontinuity

Linear interfaces from within the heteronanotubes between carbon nanotubes (CNTs) and h-BN nanotubes (BNNTs) introduce unexpected electronic and spintronic properties that are different from individual components. In particular, for heteronanotubes with zigzag boundaries (ZCBNNTs) polar discontinuities occur at the interfaces, generating an intrinsic electric field acting on the segment CNTs. In turn, the electric field will cause a charge transfer between the two interfaces to compensate for the potential difference, thus the interface states (or boundary states) show new phenomena. For example, the half-metallic can be found in ZCBNNTs. Furthermore, the length and diameter of the ZCBNNTs can effectively adjust the electronic properties, due to the compensatory effects of the free charge to the polarization charge. Our results shed light on the future design of miniature superconducting spintronic devices and the realization of high performance nanoelectronic devices with negligible interface contact resistance barriers.

Structural characterization of the LaInO3/BaSnO3 interface via synchrotron scattering

The alkaline earth stannate BaSnO3 is a semiconductor with high carrier mobility at room-temperature when doped with La3+. When a thin epitaxial layer of LaInO3 is grown on lightly doped BaSnO3, a polar discontinuity between the orthorhombic, polar LaInO3 and the cubic, nonpolar Ba0.998La0.002SnO3 leads to an electronic reconstruction, where LaInO3 remotely dopes Ba0.998La0.002SnO3, creating carriers for high mobility devices. We determine aspects of the crystalline structure of the LaInO3/BaSnO3 film that affect the polar discontinuity using synchrotron x-ray diffraction. Specifically, we examine the role of oxygen octahedral rotations and anti-parallel cation displacements in influencing the polarization of the LaInO3/BaSnO3 interface. These structural distortions are characterized by measuring half-order Bragg peaks of thin film LaInO3/BaSnO3/SrTiO3 heterostructures grown by pulsed laser deposition. We find that for films as thin as 3 unit cells, epitaxial LaInO3 has 2 distinct domains, one with the same Glazer tilt pattern as that of bulk LaInO3, a+b−b−, and a second rotated 90° in-plane from the first and having tilt pattern b−a+b−. Additionally, we observe a sudden and large increase in cation displacements along the [011] and [101] directions across the LaInO3/BaSnO3 interface due to the strength of the octahedral rotations.

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

The properties of stress-free and biaxially strained stoichiometric $\mathrm{SrTi}{\mathrm{O}}_{3}$ in the absence and presence of antiferrodistortive (AFD) distortion were calculated ab initio. To obtain reliable results, multiple exchange correlation (XC) functionals, including the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, were used. HSE was the primary XC functional, while another functional provided a good lower bound of ferroelectricity (FE). The reliability of the calculations was further reinforced by the calculations of the strain and AFD dependence. In contrast with previous works, we show that the ferroelectric phase (${C}_{4\mathrm{v}}^{1}$, ${C}_{4\mathrm{v}}^{10}$) is more stable in the absence of quantum and thermal fluctuations than the paraelectric phase (${O}_{\mathrm{h}}^{1}$, ${D}_{4\mathrm{h}}^{18}$), even for the stress-free case, and clarify the properties of these FE phases. The energy gain of stress-free FE, in comparison with the thermal and quantum fluctuation energy, indicates that a paraelectric phase emerges at room temperature by thermal fluctuations, but is near 0 K marginally close to the FE phase, which aligns with the experimental incipient FE. This implies that the paraelectricity of stress-free $\mathrm{SrTi}{\mathrm{O}}_{3}$ in experiments contains incoherent atomic-scale FE regions. These results are consistent with the FE microregions (FMR), signatures of polar disorders, and the emergence of FE in $\mathrm{SrTi}{\mathrm{O}}_{3}$ due to impurities and defects. The value of spontaneous polarization ${P}_{\mathrm{S}}$ could reach $10\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{C}/\mathrm{c}{\mathrm{m}}^{2}$ in the absence of fluctuations, even for the stress-free case. In view of the earlier theory of the carrier layer at polar discontinuities, the present results may explain the conduction at the interfaces of the $\mathrm{LaAl}{\mathrm{O}}_{3}/\mathrm{SrTi}{\mathrm{O}}_{3}$. In addition, an ``enhancement of FE due to symmetry constriction'' is proposed as an additional mechanism to the strain-enhanced FE in the epitaxial effect. For large compressive strain, e.g., 2%, the Perdew-Burke-Ernzerhof density functional for solids (PBEsol) yielded properties with ${P}_{\mathrm{S}}g20\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{C}/\mathrm{c}{\mathrm{m}}^{2}$, agreeing with HSE, and therefore is usable as a practical substitute of HSE for $\mathrm{SrTi}{\mathrm{O}}_{3}$.

Predicting ultrafast Dirac transport channel at the one-dimensional interface of the two-dimensional coplanar ZnO/MoS2 heterostructure

The discovery of high-mobility electron gas at the two-dimensional (2D) LaAlO3/SrTiO3 heterointerface [A. Ohtomo and H. Hwang, Nature (London) 427, 423 (2004)10.1038/nature02308] has attracted great research interest due to the ballistic transport of spatially confined electrons. When such kind of valence discontinuity extends to the interface of a well-chosen in-planar 2D heterostructure, a one-dimensional (1D) confined interface can be generated. Herein, through first-principles modeling, we demonstrate that Dirac-cone-like bands emerge at the 1D zigzag interface of a ZnO/MoS2 lateral heterostructure (LHS), creating a highly mobile 1D transport channel with a high Fermi velocity of 4.5×105m/s. The metallic state at the 1D heterointerface is attributed to the polar discontinuity that introduces excess charge carriers. Nontrivial polarization (excess carriers appear at boundaries) results in a large built-in electric field within the ZnO and MoS2 monolayers. Remarkably, the ultrafast 1D conducting channel is independent of the arrangements of width (m and n) in the (ZnO)m(MoS2)n LHS, which are further illustrated by tight-binding-based orbital and polarization analysis.

Valence mediated tunable magnetism and electronic properties by ferroelectric polarization switching in 2D FeI2/In2Se3 van der Waals heterostructures.

Exploring two-dimensional (2D) materials with both ferromagnetic and ferroelectric properties is scientifically interesting and of great technical importance to numerous functionalities in nanoscale devices. In this work, we have demonstrated a strong magnetoelectric coupling that appeared in the 2D FeI2/In2Se3 van der Waals heterostructure. FeI2 layers undergo a transition from ferromagnetic to antiferromagnetic by reversing the direction of ferroelectric polarization. First-principles calculation predicts a new magnetoelectronic coupling mechanism which is completely different from the Dzyaloshinskii-Moriya (DM) effect in multiferroic materials. Because of the polarization discontinuity at the interface, the valence states of Fe ions change between +2 and +3 for two different polarization directions, leading to the magnetic interaction variation between the direct exchange and I ion mediated superexchange. Moreover, metallic 2D electron gas (2DEG) transfers from the surface of FeI2 to In2Se3 when the polarization reverses, which induces the spin polarization of the heterostructure varying from 93% to 0%. Our work is the first realization of manipulation magnetism by an electric field in full 2D van der Waals heterostructures.

Interface properties and built-in potential profile of a LaCrO3/SrTiO3 superlattice determined by standing-wave excited photoemission spectroscopy

LaCrO$_3$ (LCO) / SrTiO$_3$ (STO) heterojunctions are intriguing due to a polar discontinuity along (001), two distinct and controllable interface structures [(LaO)$^+$/(TiO$_2$)$^0$ and (SrO)$^0$/(CrO$_2$)$^-$], and interface-induced polarization. In this study, we have used soft- and hard x-ray standing-wave excited photoemission spectroscopy (SW-XPS) to generate a quantitative determination of the elemental depth profiles and interface properties, band alignments, and the depth distribution of the interface-induced built-in potentials in the two constituent oxides. We observe an alternating charged interface configuration: a positively charged (LaO)$^+$/(TiO$_2$)$^0$ intermediate layer at the LCO$_\textbf{top}$/STO$_\textbf{bottom}$ interface and a negatively charged (SrO)$^0$/(CrO$_2$)$^-$ intermediate layer at the STO$_\textbf{top}$/LCO$_\textbf{bottom}$ interface. Using core-level SW data, we have determined the depth distribution of species, including through the interfaces, and these results are in excellent agreement with scanning transmission electron microscopy and electron energy loss spectroscopy (STEM-EELS) mapping of local structure and composition. SW-XPS also enabled deconvolution of the LCO-contributed and STO- contributed matrix-element-weighted density of states (MEWDOSs) from the valence band (VB) spectra for the LCO/STO superlattice (SL). Monitoring the VB edges of the deconvoluted MEWDOS shifts with a change in probing profile, the alternating charge- induced built-in potentials are observed in both constituent oxides. Finally, using a two-step simulation approach involving first core-level binding energy shifts and then valence-band modeling, the built-in potential gradients across the SL are resolved in detail and represented by the depth distribution of VB edges.

Band-Gap Reduction in (BiCrO3)m/(BiFeO3)n Superlattices: Designing Low-Band-Gap Ferroelectrics

Author(s): Zhang, S; Xiao, HY; Peng, SM; Yang, GX; Liu, ZJ; Zu, XT; Li, S; Singh, DJ; Martin, LW; Qiao, L | Abstract: Ferroelectric BiFeO3 is promising for photovoltaic applications, especially in regard to the exploitation of ferroelectric photovoltaic effects for charge separation. However, its large band gap limits efficient sunlight absorption. Here, we demonstrate a new strategy to effectively tune the band gap of tetragonal BiFeO3 via superlattice structuring with the ferroelectric BiCrO3. The (BiCrO3)m/(BiFeO3)n superlattices are found to exhibit conventional ferroelectric properties, but low fundamental band gaps, smaller than either of the parent materials. First-principles calculations reveal that the unexpected band-gap reduction is induced by charge reconstruction due to lattice strain, octahedral distortion, and polarization discontinuity at the BiCrO3-BiFeO3 interfaces. Ultimately, these results provide a new strategy, in the form of superlattice structuring, which could open the door to the creation of efficient ferroelectric photovoltaics.

Electrostatic potential and valence modulation in La0.7Sr0.3MnO3 thin films

The Mn valence in thin film La0.7Sr0.3MnO3 was studied as a function of film thickness in the range of 1–16 unit cells with a combination of non-destructive bulk and surface sensitive X-ray absorption spectroscopy techniques. Using a layer-by-layer valence model, it was found that while the bulk averaged valence hovers around its expected value of 3.3, a significant deviation occurs within several unit cells of the surface and interface. These results were supported by first principles calculations. The surface valence increases to up to Mn3.7+, whereas the interface valence reduces down to Mn2.5+. The change in valence from the expected bulk value is consistent with charge redistribution due to the polar discontinuity at the film-substrate interface. The comparison with theory employed here illustrates how this layer-by-layer valence evolves with film thickness and allows for a deeper understanding of the microscopic mechanisms at play in this effect. These results offer insight on how the two-dimensional electron gas is created in thin film oxide alloys and how the magnetic ordering is reduced with dimensionality.

Anisotropic polarization-induced conductance at a ferroelectric-insulator interface.

Coupling between different degrees of freedom, that is, charge, spin, orbital and lattice, is responsible for emergent phenomena in complex oxide heterostrutures1,2. One example is the formation of a two-dimensional electron gas (2DEG) at the polar/non-polar LaAlO3/SrTiO3 (LAO/STO)3-7 interface. This is caused by the polar discontinuity and counteracts the electrostatic potential build-up across the LAO film3. The ferroelectric polarization at a ferroelectric/insulator interface can also give rise to a polar discontinuity8-10. Depending on the polarization orientation, either electrons or holes are transferred to the interface, to form either a 2DEG or two-dimensional hole gas (2DHG)11-13. While recent first-principles modelling predicts the formation of 2DEGs at the ferroelectric/insulator interfaces9,10,12-14, experimental evidence of a ferroelectrically induced interfacial 2DEG remains elusive. Here, we report the emergence of strongly anisotropic polarization-induced conductivity at a ferroelectric/insulator interface, which shows a strong dependence on the polarization orientation. By probing the local conductance and ferroelectric polarization over a cross-section of a BiFeO3-TbScO3 (BFO/TSO) (001) heterostructure, we demonstrate that this interface is conducting along the 109° domain stripes in BFO, whereas it is insulating in the direction perpendicular to these domain stripes. Electron energy-loss spectroscopy and theoretical modelling suggest that the anisotropy of the interfacial conduction is caused by an alternating polarization associated with the ferroelectric domains, producing either electron or hole doping of the BFO/TSO interface.