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See detailRaman signatures of ferroic domain walls captured by principal component analysis
Nataf, G. F.; Barrett, N.; Kreisel, Jens UL et al

in JOURNAL OF PHYSICS-CONDENSED MATTER (2018), 30(3),

Ferroic domain walls are currently investigated by several state-of-the art techniques in order to get a better understanding of their distinct functional properties. Here, principal component analysis ... [more ▼]

Ferroic domain walls are currently investigated by several state-of-the art techniques in order to get a better understanding of their distinct functional properties. Here, principal component analysis (PCA) of Raman maps is used to study ferroelectric domain walls (DWs) in LiNbO3 and ferroelastic DWs in NdGaO3. It is shown that PCA allows us to quickly and reliably identify small Raman peak variations at ferroelectric DWs and that the value of a peak shift can be deduced-accurately and without a priori-from a first order Taylor expansion of the spectra. The ability of PCA to separate the contribution of ferroelastic domains and DWs to Raman spectra is emphasized. More generally, our results provide a novel route for the statistical analysis of any property mapped across a DW. [less ▲]

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See detailControl of surface potential at polar domain walls in a nonpolar oxide
Nataf, G. F.; Guennou, Mael UL; Kreisel, Jens UL et al

in PHYSICAL REVIEW MATERIALS (2017), 1(7),

Ferroic domain walls could play an important role in microelectronics given their nanometric size and often distinct functional properties. Until now, devices and device concepts were mostly based on ... [more ▼]

Ferroic domain walls could play an important role in microelectronics given their nanometric size and often distinct functional properties. Until now, devices and device concepts were mostly based on mobile domain walls in ferromagnetic and ferroelectric materials. A less explored path is to make use of polar domain walls in nonpolar ferroelastic materials. Indeed, while the polar character of ferroelastic domain walls has been demonstrated, polarization control has been elusive. Here, we report evidence for the electrostatic signature of the domain-wall polarization in nonpolar calcium titanate (CaTiO3). Macroscopic mechanical resonances excited by an ac electric field are observed as a signature of a piezoelectric response caused by polar walls. On the microscopic scale, the polarization in domain walls modifies the local surface potential of the sample. Through imaging of surface potential variations, we show that the potential at the domain wall can be controlled by electron injection. This could enable devices based on nondestructive information readout of surface potential. [less ▲]

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See detailLow energy electron imaging of domains and domain walls in magnesium-doped lithium niobate
Nataf, G. F.; Grysan, P.; Guennou, Mael UL et al

in SCIENTIFIC REPORTS (2016), 6

The understanding of domain structures, specifically domain walls currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in ... [more ▼]

The understanding of domain structures, specifically domain walls currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM - electrons reflected) to Low Energy Electron Microscopy (LEEM - electrons backscattered) gives rise to a robust contrast between domains with upwards (P-up) and downwards (P-down) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field. [less ▲]

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