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Real-Time 3D Imaging of Nanoscale Ferroelectric Domain Wall Dynamics in Lithium Niobate Single Crystals under Electric Stimuli: Implications for Domain-Wall-Based Nanoelectronic Devices
journal contribution
posted on 2019-09-11, 18:40 authored by Benjamin Kirbus, Christian Godau, Lukas Wehmeier, Henrik Beccard, Elke Beyreuther, Alexander Haußmann, Lukas M. EngChallenges
in the fields of renewable energy harvesting, data storage,
and nanoelectronics have resparked interest in ferroelectric domain
walls (DWs) as tunable, nanoscale elements. However, the study of
such structures has mostly relied on 2-dimensional, rather slow imaging
techniques such as scanning probe microscopy. Therefore, Cherenkov
second harmonic generation (CSHG) microscopy has been established
as a technique suitable for the nondestructive imaging of ferroelectric
DWs and their 3-dimensional (3D) evolution. Here, we report on the
real-time and in situ 3D DW kinetics when inspecting
electrical-field-biased 200 μm thick lithium niobate (LNO) single
crystals. A linear electric field increase up to +4.0 kV/mm (antiparallel
to the direction of spontaneous polarization PS) resulted in the collapse of laser-poled hexagonal domains
into cone-like structures. The average inclination was measured to
rise up to 2.5°. Head-to-head (h2h) domain walls dominated. Simultaneously,
the domain wall current (DWC) was recorded in situ. It increased by 4 orders of magnitude to 1 μA. The DW mobility
increased dramatically as a function of depth. Moreover, a significant
asymmetry was found, as DW mobility was much higher along crystallographic
(Y+) directions. Subsequently, the electric field
was reversed and swept to −3.6 kV/mm. While the hexagonal domain
shapes were restored for moderate electric fields, the domains separated
into many nucleating spike domains when exceeding a critical threshold
of −3.5 kV/mm. DWC increased dramatically through this process,
reaching magnitudes of up to 1 mA. The understanding of DW dynamics
upon electric stimulation was used to realize a two-port DW-based
nanoswitch. Alternating positive and negative electric fields were
applied to a neutral hexagonal domain contacted purely via solid electrodes.
The field strengths were kept well below the critical threshold of
spike domain formation. The electrical conductivity of such a device
could be tuned over 4 orders of magnitude, i.e., deliberately switched
on and off. Our findings support the development of future DW-based
nanoelectronic devices.
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3 D DW kineticsDW mobilityDomain-Wall-Based Nanoelectronic Devices Challengesscanning probe microscopynucleating spike domainsfuture DW-based nanoelectronic deviceselectrical-field-biased 200 μ mLithium Niobate Single CrystalsLNO4 orderspolarization P Stwo-port DW-based nanoswitchCSHGNanoscale Ferroelectric Domain Wall DynamicsReal-Time 3 D Imagingh 2h domain wallsspike domain formationDWC
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