Imaging the local electrical properties of metal surfaces by atomic force microscopy with conducting probes

Houzé, Frédéric; Meyer, René; Schneegans, Olivier; Boyer, L.

doi:10.1063/1.117179

Cited by 175 publications

(101 citation statements)

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“…The Fe layers were grown by RF sputtering at room temperature and covered by a naturally oxidized Al layer, resulting in a AlO x (1.5 nm)/Al(1.5 nm) cap. The tunnel junctions were defined by nanoindentation lithography 46,47 with top electrodes of either Au/CoO/Co or Au/CoO/Co/Fe (see also ref. 26 for details on the role of CoO).…”

Section: Methodsmentioning

confidence: 99%

Interface-induced room-temperature multiferroicity in BaTiO3

et al. 2011

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Multiferroic materials possess two or more ferroic orders but have not been exploited in devices owing to the scarcity of room-temperature examples. Those that are ferromagnetic and ferroelectric have potential applications in multi-state data storage if the ferroic orders switch independently, or in electric-field controlled spintronics if the magnetoelectric coupling is strong. Future applications could also exploit toroidal moments and optical effects that arise from the simultaneous breaking of time-reversal and space-inversion symmetries. Here, we use soft X-ray resonant magnetic scattering and piezoresponse force microscopy to reveal that, at the interface with Fe or Co, ultrathin films of the archetypal ferroelectric BaTiO 3 simultaneously possess a magnetization and a polarization that are both spontaneous and hysteretic at room temperature. Ab initio calculations of realistic interface structures provide insight into the origin of the induced moments and bring support to this new approach for creating room-temperature multiferroics.

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Section: Methodsmentioning

confidence: 99%

Interface-induced room-temperature multiferroicity in BaTiO3

et al. 2011

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“…The CT-AFM is based on a Digital Instruments Nanoscope III multimode AFM, which was modified by Houzé et al to perform local resistance measurements in the range of 100 to 10 12 ohms with 5% accuracy under a bias voltage ranging from 0.1 to 10 V [26]. The LAO/STO cross-sectional samples for measurements of the local resistance with CT-AFM were cut through the contacts described above and glued together front-to-front (as for a TEM cross section) so that the contacts remained usable.…”

Section: Sample Preparation For Ct-afm Charaterization Of Lao/sto Strmentioning

confidence: 99%

Mapping the spatial distribution of charge carriers in LaAlO3/SrTiO3 heterostructures

Basletić

Maurice²,

Carrétéro³

et al. 2008

Nature Mater

431

386

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At the interface between complex insulating oxides, novel phases with interesting properties may occur, such as the metallic state reported in the LaAlO 3 /SrTiO 3 system [1].While this state has been predicted [2] and reported [3,4] to be confined at the interface, some works indicate a much broader spatial extension [5], thereby questioning its origin. Here we provide for the first time a direct determination of the carrier density profile of this system through resistance profile mappings collected in cross-section LaAlO 3 /SrTiO 3 samples with a conducting-tip atomic force microscope (CT-AFM). We find that, depending upon specific growth protocols, the spatial extension of the high-mobility electron gas can be varied from hundreds of microns into SrTiO 3 to a few nanometers next to the LaAlO 3 /SrTiO 3 interface.Our results emphasize the potential of CT-AFM as a novel tool to characterize complex oxide interfaces and provide us with a definitive and conclusive way to reconcile the body of experimental data in this system 2 Due to the richness of their intrinsic properties oxide materials can bring novel functionalities to electronics. Among all oxides, SrTiO 3 (STO) is particularly appealing because of its multifunctional character. It is a wide band gap semiconductor (3.2 eV) that becomes a high mobility metal [6] or even superconducting [7] upon oxygen vacancy doping.Stoichiometric STO is also at the fringe of ferroelectricity and its large dielectric permittivity, tunability and low microwave loss, makes it a good candidate for tunable microwave devicesThe potential of oxides is further enlarged by the fascinating properties of their interfaces, epitomized by the observation of ferromagnetism at the interface between two antiferromagnets [9] or of the quantum Hall effect in two-dimensional (2D) ZnO-based structures [10]. Recently, an electron gas with high electron mobility at low temperature (in the 10 4 cm 2 /Vs range) has been reported in heterostructures combining STO with LaAlO 3 (LAO), another band insulator [1]. Since its discovery by Ohtomo and Hwang [1], this unusual metallic state has been the object of many studies [2,3,4,5,11,12,13,14,15,16,17,18].Recent results include a two-dimensional superconducting behaviour at the LAO/STO interface below 200 mK [19], and indications of a ferromagnetic state below ~1K [20].The arguments invoked to explain the metallic state observed in such LAO/STO samples have been dual. A first interpretation relies on the transfer of a ½ e charge per unit cell at the interface, because of the polar discontinuity between positively charged LaO and neutral TiO 2 sub-planes [11]. In this picture a sheet carrier density n sheet ≈ 3.3 10 14 cm -2 is expected. However, in many cases the reported values of n sheet exceed this density by orders of magnitude [1,5,17]. This leads to another interpretation relying on the creation of oxygen vacancies in the STO substrate during the growth of the LAO film, which dopes the STO with electrons and makes it a high-mobility meta...

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“…19 Resistance mappings of 20 μm × 20 μm regions were collected, by applying a bias voltage of 1 V, at room temperature with a 10 −12 -10 −4 A current range and Si 3 N 4 tips coated with B-doped diamond.…”

Section: Introductionmentioning

confidence: 99%

Epitaxial growth and ferrimagnetic behavior of MnFe2O4(111) ultrathin layers for room-temperature spin filtering

et al. 2011

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We report on the epitaxial growth and physical properties of spinel MnFe 2 O 4 (111) thin films with thicknesses down to 2 nm. The thin films, grown on α-Al 2 O 3 (0001) single crystals or Pt(111) buffer layers by oxygen-assisted molecular beam epitaxy, exhibit high structural order with sharp interfaces and low roughness. The electrical and magnetic properties are carefully investigated and it is shown that MnFe 2 O 4 (111) ultrathin films keep an insulating and ferrimagnetic behavior at room temperature. Special attention is given to the iron/manganese valence state and the cationic ordering. X-ray absorption spectroscopy and magnetic circular dichroism measurements reveal that thin films contain mainly Fe 3+ and Mn 2+ cations, distributed predominantly in a normal spinel structure. This study proves the high potential of MnFe 2 O 4 to be used as a magnetic tunnel barrier for spin filtering applications at room temperature.

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Imaging the local electrical properties of metal surfaces by atomic force microscopy with conducting probes

Cited by 175 publications

References 1 publication

Interface-induced room-temperature multiferroicity in BaTiO3

Interface-induced room-temperature multiferroicity in BaTiO3

Mapping the spatial distribution of charge carriers in LaAlO3/SrTiO3 heterostructures

Epitaxial growth and ferrimagnetic behavior of MnFe2O4(111) ultrathin layers for room-temperature spin filtering

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