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A diode for ferroelectric domain-wall motion.

Whyte JR, Gregg JM - Nat Commun (2015)

Bottom Line: Revolutionary technologies have resulted, like racetrack memory and domain-wall logic.Until recently, equivalent research in analogous ferroic materials did not seem important.Domain walls can move readily in the direction in which thickness increases gradually, but are prevented from moving in the other direction by the sudden thickness increase at the sawtooth edge.

View Article: PubMed Central - PubMed

Affiliation: Centre for Nanostructured Media, School of Maths and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, UK.

ABSTRACT
For over a decade, controlling domain-wall injection, motion and annihilation along nanowires has been the preserve of the nanomagnetics research community. Revolutionary technologies have resulted, like racetrack memory and domain-wall logic. Until recently, equivalent research in analogous ferroic materials did not seem important. However, with the discovery of sheet conduction, the control of domain walls in ferroelectrics has become vital for the future of what has been termed 'domain-wall electronics'. Here we report the creation of a ferroelectric domain-wall diode, which allows a single direction of motion for all domain walls, irrespective of their polarity, under a series of alternating electric field pulses. The diode's sawtooth morphology is central to its function. Domain walls can move readily in the direction in which thickness increases gradually, but are prevented from moving in the other direction by the sudden thickness increase at the sawtooth edge.

No MeSH data available.


Experimental setup and domain dynamics of a terraced KTP lamella.Schematic illustration of a KTiOPO4 (KTP) ferroelectric lamella cut into terraces of different thickness and incorporated into a coplanar capacitor structure (a). In b, a line profile of the topography of a terrace-cut sample, measured using atomic force microscopy (AFM), is presented, showing well-defined steps in thickness. Inset is a plan-view image of the AFM topography scan and the trace of the line section shown is highlighted in blue. PFM scans (c) show the extent to which polarization reorientation occurs as a function of thickness from an initially fully poled state. In this terraced sample the thinnest region (∼400nm thick) has been fully switched in the reverse sense; in the region of intermediate thickness (∼500 nm) ∼60% switched and the thickest region (∼600 nm) only ∼15% switched. It appears that, in this geometry, thickness is strongly correlated with switching dynamics. The scale bar is 3 μm in length.
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f2: Experimental setup and domain dynamics of a terraced KTP lamella.Schematic illustration of a KTiOPO4 (KTP) ferroelectric lamella cut into terraces of different thickness and incorporated into a coplanar capacitor structure (a). In b, a line profile of the topography of a terrace-cut sample, measured using atomic force microscopy (AFM), is presented, showing well-defined steps in thickness. Inset is a plan-view image of the AFM topography scan and the trace of the line section shown is highlighted in blue. PFM scans (c) show the extent to which polarization reorientation occurs as a function of thickness from an initially fully poled state. In this terraced sample the thinnest region (∼400nm thick) has been fully switched in the reverse sense; in the region of intermediate thickness (∼500 nm) ∼60% switched and the thickest region (∼600 nm) only ∼15% switched. It appears that, in this geometry, thickness is strongly correlated with switching dynamics. The scale bar is 3 μm in length.

Mentions: For initial investigations into the way in which thickness might affect domain-wall mobility, a terraced lamella (thin slice) was manufactured from a bulk single crystal of uniaxial ferroelectric KTiOPO4 (KTP) and integrated into a coplanar capacitor geometry (Fig. 2a). The terraced topography was FIB milled into one face of the lamella, while the other face was left flat to ensure good electrical contact with the coplanar electrodes. Atomic force microscopy (AFM) showed well-defined steps on the lamellar face (Fig. 2b). After completely poling this lamella in one sense, piezoresponse force microscopy (PFM) was used to image the extent to which switching occurred after a 1 s 60 V reverse pulse was applied across the capacitor. As is evident in Fig. 2c, the dynamics of switching were very different in the three regions of different thickness: switching was significantly accelerated in the thinnest section. This intriguing observation prompted a different strategy for site-specific domain-wall injection in the test diode structure subsequently fabricated than had been developed in previous research, where engineered local-field hot spots had been used1819. Instead, here the newly established link between reduced thickness and a lowering in coercivity allowed a domain-wall injection pad, analogous to those used in nanomagnetism2930, to be realized.


A diode for ferroelectric domain-wall motion.

Whyte JR, Gregg JM - Nat Commun (2015)

Experimental setup and domain dynamics of a terraced KTP lamella.Schematic illustration of a KTiOPO4 (KTP) ferroelectric lamella cut into terraces of different thickness and incorporated into a coplanar capacitor structure (a). In b, a line profile of the topography of a terrace-cut sample, measured using atomic force microscopy (AFM), is presented, showing well-defined steps in thickness. Inset is a plan-view image of the AFM topography scan and the trace of the line section shown is highlighted in blue. PFM scans (c) show the extent to which polarization reorientation occurs as a function of thickness from an initially fully poled state. In this terraced sample the thinnest region (∼400nm thick) has been fully switched in the reverse sense; in the region of intermediate thickness (∼500 nm) ∼60% switched and the thickest region (∼600 nm) only ∼15% switched. It appears that, in this geometry, thickness is strongly correlated with switching dynamics. The scale bar is 3 μm in length.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490414&req=5

f2: Experimental setup and domain dynamics of a terraced KTP lamella.Schematic illustration of a KTiOPO4 (KTP) ferroelectric lamella cut into terraces of different thickness and incorporated into a coplanar capacitor structure (a). In b, a line profile of the topography of a terrace-cut sample, measured using atomic force microscopy (AFM), is presented, showing well-defined steps in thickness. Inset is a plan-view image of the AFM topography scan and the trace of the line section shown is highlighted in blue. PFM scans (c) show the extent to which polarization reorientation occurs as a function of thickness from an initially fully poled state. In this terraced sample the thinnest region (∼400nm thick) has been fully switched in the reverse sense; in the region of intermediate thickness (∼500 nm) ∼60% switched and the thickest region (∼600 nm) only ∼15% switched. It appears that, in this geometry, thickness is strongly correlated with switching dynamics. The scale bar is 3 μm in length.
Mentions: For initial investigations into the way in which thickness might affect domain-wall mobility, a terraced lamella (thin slice) was manufactured from a bulk single crystal of uniaxial ferroelectric KTiOPO4 (KTP) and integrated into a coplanar capacitor geometry (Fig. 2a). The terraced topography was FIB milled into one face of the lamella, while the other face was left flat to ensure good electrical contact with the coplanar electrodes. Atomic force microscopy (AFM) showed well-defined steps on the lamellar face (Fig. 2b). After completely poling this lamella in one sense, piezoresponse force microscopy (PFM) was used to image the extent to which switching occurred after a 1 s 60 V reverse pulse was applied across the capacitor. As is evident in Fig. 2c, the dynamics of switching were very different in the three regions of different thickness: switching was significantly accelerated in the thinnest section. This intriguing observation prompted a different strategy for site-specific domain-wall injection in the test diode structure subsequently fabricated than had been developed in previous research, where engineered local-field hot spots had been used1819. Instead, here the newly established link between reduced thickness and a lowering in coercivity allowed a domain-wall injection pad, analogous to those used in nanomagnetism2930, to be realized.

Bottom Line: Revolutionary technologies have resulted, like racetrack memory and domain-wall logic.Until recently, equivalent research in analogous ferroic materials did not seem important.Domain walls can move readily in the direction in which thickness increases gradually, but are prevented from moving in the other direction by the sudden thickness increase at the sawtooth edge.

View Article: PubMed Central - PubMed

Affiliation: Centre for Nanostructured Media, School of Maths and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, UK.

ABSTRACT
For over a decade, controlling domain-wall injection, motion and annihilation along nanowires has been the preserve of the nanomagnetics research community. Revolutionary technologies have resulted, like racetrack memory and domain-wall logic. Until recently, equivalent research in analogous ferroic materials did not seem important. However, with the discovery of sheet conduction, the control of domain walls in ferroelectrics has become vital for the future of what has been termed 'domain-wall electronics'. Here we report the creation of a ferroelectric domain-wall diode, which allows a single direction of motion for all domain walls, irrespective of their polarity, under a series of alternating electric field pulses. The diode's sawtooth morphology is central to its function. Domain walls can move readily in the direction in which thickness increases gradually, but are prevented from moving in the other direction by the sudden thickness increase at the sawtooth edge.

No MeSH data available.