Surface Conduction on Poled BaTiO<sub>3</sub>Single Crystals in Ultra High Vacuum

Urakami, Yosuke; Yamato, Mizuki; Watanabe, Yoshihisa

doi:10.1080/00150190601180158

Cited by 13 publications

(7 citation statements)

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“…Depending on the polarization direction the topmost ML undergoes a transition from metallic to oxide behavior shows metallic or oxide behavior. As a consequence the in-plane conductance changes drastically which is a reasonable explanation of the experimental results by Urakami et al 27 .…”

supporting

confidence: 89%

“…But nevertheless the electronic structure of the surface layer changes from metallic to oxide behavior under reversal of polarization which changes the surface conductance drastically. 27 This may have important implications in the design of multiferroic nano-devices.…”

Section: Figmentioning

confidence: 99%

“…Recently, Urakami et al 27 have observed the surface conductance of BaTiO 3 single crystals in ultra high vacuum below T C . It has been shown that the in-plane conductance is the result of an intrinsic surface electron/hole layer that is, due to the surface polarity and not due to O vacancies or some other defects.…”

mentioning

confidence: 99%

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Effect of the surface polarization in polar perovskites studied from first principles

2008

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The (001) surfaces of polar perovskites BaTiO3 and PbTiO3 have been studied from first principles at T=0 K. For both cases of polarization, the most stable TiO-terminated interfaces show intrinsic ferroelectricity. In the topmost layer, where the O atoms are >0.1Å above Ti, this leads to metallic instead of the insulating behavior of the electronic states that may have important implications for multiferroic tunneling junctions.PACS numbers: 31.15. 68.47.Gh, 73.20.At, 77.84.Dy, Epitaxial growth technique opens the way to combine ferroelectrics (FE) and ferromagnets (FM) into multicomponent multiferroics, which are inaccessible by traditional synthesis.1,2 Currently, many laboratories across the world work on a prototypic device, consisting of a few-nm thick ferroelectric sandwiched between a ferromagnet and another metallic contact. External electric field applied to the FE phase causes a switching of its polarization P that, in turn, through the magnetoelectric coupling may change the magnetic order in the ferromagnetic phase.3 Altering P and magnetization independently for encoding information in multiferroics, the smallest quaternary logical memory might be obtained. Fundamentally new multiferroics require a better understanding of the FE order parameters, especially, in the case of thin films here the symmetry is reduced.Since direct measurements of atomic displacements, occurring in FE near the interface, is extremely challenging, their structures can be understood and numerically characterized from first principles. Recently, much work has been conducted to study bare FE surfaces using the ab initio density functional theory (DFT) calculations. 4,5,6,7,8,9,10,11,12 It has been found that the critical thickness down to 3 unit cells (1.2 nanometers) is enough to enable the existence of ferroelectricity at room temperature.13,14,15 However, there are only some convincing evidences in literature i.e. the work by Cohen 5 that the direction of P may affect the surface relaxation. The functionality of multiferroics assumes that P must be reversible and parallel to the surface normal. Hence, it is worthwhile to carry out ab initio calculations which model the reaction of the (001) surface of polar ferroelectric surfaces upon the change of its reversible P.In this report, we study the (001) surface of ABO 3 perovskites (A = Sr, Ba, Pb and B = Ti), which represent a wide class of ferroelectrics ranging from paraelectric SrTiO 3 (STO) to highly polar PbTiO 3 (PTO), while BaTiO 3 (BTO), with its moderate spontaneous polarization P s , is an example of a typical FE. The study is based on extensive calculations, using the Vienna Abinitio Simulation Package 16 (VASP), in which the effects of relaxation of atomic positions are included. Nowadays, many FE properties can be successfully calculated from first principles.17 Table I collects the experimental data for the lattice parameters and atomic positions, obtained for the room-temperature tetragonal phase of PTO and BTO (with space group symmetry P 4mm) and for cubic ST...

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confidence: 99%

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Effect of the surface polarization in polar perovskites studied from first principles

2008

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“…These three perovskites are all classified as incipient ferroelectrics in which quantum fluctuations prevent a ferroelectric order [28][29][30][31]. Two-dimensional states can also be expected at the surface of BTO, which presents an excellent opportunity to study the impact of bulk ferroelectric order on these twodimensional states at the surface and their transport properties [32]. It also offers a means of inducing ferroelectricity in other perovskites through doping or multilayer structure assembly.…”

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confidence: 99%

Influence of ferroelectric order on the surface electronic structure ofBaTiO3films studied by photoemission spectroscopy

et al. 2018

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The electronic structure of in situ grown ferroelectric BaTiO 3 (001) films is studied by angle-resolved photoemission spectroscopy. A two-dimensional state is found at the film-vacuum interface with an unexpected checkerboardlike Fermi surface. The observed absence of in-plane dispersion of the states is attributed to the influence of the strong electric fields of the ferroelectric bulk of the film. These fields cause Bloch oscillations and Wannier-Stark localization of free charges in real space, resulting in a smearing in reciprocal space. It is shown that this effect extends to thin SrTiO 3 overlayers grown on the BaTiO 3 film.

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“…These three perovskites are all classified as incipient ferroelectrics in which quantum fluctuations prevent a ferroelectric order [19][20][21][22]. Two-dimensional states can also be expected at the surface of BTO, which presents an excellent opportunity to study the impact of bulk ferroelectric order on these two-dimensional states at the surface and their transport properties [23]. It also offers a means of inducing ferroelectricity in other perovskites through doping or multilayer structure assembly.…”

mentioning

confidence: 99%

Observation of Wannier-Stark localization at the surface of BaTiO$_3$ films by photoemission

Muff,

Pilet,

Fanciulli

et al. 2017

Preprint

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Observation of Bloch oscillations and Wannier-Stark localization of charge carriers is typically impossible in single-crystals, because an electric field higher than the breakdown voltage is required. In BaTiO3 however, high intrinsic electric fields are present due to its ferroelectric properties. With angle-resolved photoemission we directly probe the Wannier-Stark localized surface states of the BaTiO3 film-vacuum interface and show that this effect extends to thin SrTiO3 overlayers. The electrons are found to be localized along the in-plane polarization direction of the BaTiO3 film.

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Surface Conduction on Poled BaTiO₃Single Crystals in Ultra High Vacuum

Cited by 13 publications

References 5 publications

Effect of the surface polarization in polar perovskites studied from first principles

Effect of the surface polarization in polar perovskites studied from first principles

Influence of ferroelectric order on the surface electronic structure ofBaTiO3films studied by photoemission spectroscopy

Observation of Wannier-Stark localization at the surface of BaTiO$_3$ films by photoemission

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Surface Conduction on Poled BaTiO3Single Crystals in Ultra High Vacuum

Cited by 13 publications

References 5 publications

Effect of the surface polarization in polar perovskites studied from first principles

Effect of the surface polarization in polar perovskites studied from first principles

Influence of ferroelectric order on the surface electronic structure ofBaTiO3films studied by photoemission spectroscopy

Observation of Wannier-Stark localization at the surface of BaTiO$_3$ films by photoemission

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Surface Conduction on Poled BaTiO₃Single Crystals in Ultra High Vacuum