Epitaxial strain and electric boundary condition effects on the structural and ferroelectric properties of BiFeO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>films

Johann, Florian; Morelli, Alessio; Biggemann, Daniel; Arredondo, Miryam; Vrejoiu, Ionela

doi:10.1103/physrevb.84.094105

Cited by 59 publications

(64 citation statements)

References 33 publications

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“…The atomic resolved image clearly indicates the high quality of epitaxial heterostructure with wellordered lattice structure and well defined RuO 2 /BiO interface. The STEM analysis shows that BFO epitaxially grown on SRO-covered (001)-oriented STO single crystal substrate exhibits a rhombohedrallike (R-like) c/a ratio around 1.03, which is identical with those reported previously 14,15 . Good ferroelectric quality of the film and asymmetric coercive fields are evident from the local piezoresponse phase hysteresis shown in Fig.…”

Section: Resultssupporting

confidence: 76%

“…As shown in Fig. 1d, the polarization of the as-grown BFO films on the SROcovered STO substrates has a preferred downward direction as appeared in dark area of the image 15 . After switching the polarization to the downward direction by applying a positive voltage on a conductive tip, positive screen charges are accumulated on the surface of a domain 7 .…”

Section: Resultsmentioning

confidence: 97%

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A new non-destructive readout by using photo-recovered surface potential contrast

Yang¹

2015

J Material Sci Eng

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Ferroelectric random access memory is still challenging in the feature of combination of room temperature stability, non-destructive readout and high intensity storage. As a non-contact and non-destructive information readout method, surface potential has never been paid enough attention because of the unavoidable decay of the surface potential contrast between oppositely polarized domains. That is mainly due to the recombination of the surface movable charges around the domain walls. Here, by introducing a laser beam into the combination of piezoresponse force microscopy and Kelvin probe force microscopy, we demonstrate that the surface potential contrast of BiFeO 3 films can be recovered under light illumination. The recovering mechanism is understood based on the redistribution of the photo-induced charges driven by the internal electric field. Furthermore, we have created a 12-cell memory pattern based on BiFeO 3 films to show the feasibility of such photo-assisted non-volatile and non-destructive readout of the ferroelectric memory.F erroelectric materials are promising candidates for ferroelectric random access memories (FeRAMs) using their spontaneous polarization 1 , which can be switched by an external electrical field. Although FeRAMs are non-volatile and the reading/writing process can be completed within nanoseconds 2,3 , one fatal problem for conventional FeRAMs is that the reading process, which is performed by applying a bias to the ferroelectric capacitor and detecting the polarization switching current, is destructive because a rewriting process is needed. Thus, it is highly desirable to have a non-destructive readout method [4][5][6] . Polarization reversal influences the surface potential (SP) 7 which mirrors the surface charges in the polarized regions. A clear understanding of the behavior of surface charges after poling is crucial to utilizing ferroelectricity at the nanometer scale. Despite much of the work on the study of the SP of the ferroelectric materials [8][9][10][11][12] , relatively little emphasis has been placed on the readout method by measuring the non-contact SP in a ferroelectric memory, simply because the SP contrast (DSP) between oppositely polarized domains decays and fails to be kept as a memory, which is mainly due to the evolution and recombination of the movable surface charges 7,8,11,13 around the domain walls. So far, the room-temperature stability of DSP has not been succeeded, so the high density memory based on this concept faces critical challenge.By introducing a laser beam with an optical fiber into a system for piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM), we demonstrate conceptually the decay issue of DSP between the oppositely polarized domains can be resolved by photo-assisted recovery. Under the sustained internal polarization field, photo-induced charges recover DSP, thus reproducing the memory readout signal in a non-destructive and non-volatile manner. Our theoretical calculations reproduce our experimental results, rev...

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 97%

A new non-destructive readout by using photo-recovered surface potential contrast

Yang¹

2015

J Material Sci Eng

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“…7,8 Bismuth ferrite films (thickness >26 nm) grown on (001) SrTiO 3 (STO) substrates (−1.4% compressive strain) exhibit the R-like monoclinic structure (M A ) with a c/a ratio close to unity. 8,9,14 Previous studies [15][16][17] have shown that the effects of the perovskite heterointerfaces generally extend over only a few unit cells. In particular, ultra-thin BiFeO 3 films grown on (001) SrTiO 3 substrates with a SrRuO 3 buffer layer showed evidence for a transition to tetragonal symmetry.…”

mentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11] The bulk form of BiFeO 3 is known to have a rhombohedrally distorted quasi-cubic perovskite structure with an a − a − a − (Glazer notation 12 ) octahedral tilt pattern, 13 exhibiting both anti-ferrodistortive displacements and a spontaneous polarization along the 111 pseudocubic axes. When epitaxial BiFeO 3 thin films are grown under compressive strain on (001)-oriented perovskite substrates, several studies 2,4,[7][8][9] have reported that the polarization direction is tilted towards the [001] out-of-plane direction, while maintaining a significant in-plane component, depending on the amount of epitaxial strain from the substrate. This effect is accompanied by a significant enhancement of the spontaneous polarization and a series of phase transitions from rhombohedral (R) for small strains to R-like monoclinic (M A ) to T-like monoclinic (M C ) and to tetragonal (T) for larger strains, the latter two of which exhibit a giant c/a ratio.…”

mentioning

confidence: 99%

Untilting BiFeO3: The influence of substrate boundary conditions in ultra-thin BiFeO3 on SrTiO3

et al. 2013

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We report on the role of oxygen octahedral tilting in the monoclinic-to-tetragonal phase transition in ultra-thin BiFeO3 films grown on (001) SrTiO3 substrates. Reciprocal space maps clearly show the disappearance of the integer-order Bragg peak splitting associated with the monoclinic phase when the film thickness decreases below 20 unit cells. This monoclinic-to-tetragonal transition is accompanied by the evolution of the half-order diffraction peaks, which reflects untilting of the oxygen octahedra around the [110] axis, proving that the octahedral tilting is closely correlated with the transition. This structural change is thickness-dependent, and different from a strain-induced transition in the conventional sense.

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“…The films show good ferroelectricity, with out of plane polarization ~60 μC·cm -2 [11]. Arrays of 45 nm thick aluminium dots were evaporated on the BFO through stencil masks with aperture diameter of 400 nm (Figs.1a,1b) [12].…”

Section: Methodsmentioning

confidence: 99%

Mask assisted fabrication of nanoislands of BiFeO3 by ion beam milling

Morelli¹,

Johann

Schammelt

et al. 2013

Journal of Applied Physics

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Epitaxial strain and electric boundary condition effects on the structural and ferroelectric properties of BiFeO3films

Cited by 59 publications

References 33 publications

A new non-destructive readout by using photo-recovered surface potential contrast

A new non-destructive readout by using photo-recovered surface potential contrast

Untilting BiFeO3: The influence of substrate boundary conditions in ultra-thin BiFeO3 on SrTiO3

Mask assisted fabrication of nanoislands of BiFeO3 by ion beam milling

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