Imaging ferroelectric domains via charge gradient microscopy enhanced by principal component analysis

Esfahani, Ehsan Nasr; Liu, Xiaoyan; Li, Jiangyu

doi:10.1016/j.jmat.2017.07.001

Cited by 7 publications

(5 citation statements)

References 34 publications

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“…CGM is a scanning probe microscopy technique (first reported by Hong et al in 2014 [26] ), which allows spatial gradients in ferroelectric bound charge to be directly imaged, by monitoring currents passing through an earthed passive conducting AFM tip (usually solid platinum), pressed strongly into contact and rapidly scanned across the sample surface. Whether the technique involves changes in the screening charges at the surface of the metallic tip, or the "collection" of screening charge already aggregated on the ferroelectric free surface, is still a matter of debate [26][27][28][29] (see Note S2, Supporting Information). In any case though, the integration of the measured currents across stationary domain walls in CGM has been shown to reflect the switching charge associated with polar reorientation under the moving tip.…”

Section: Negative Capacitance and Measurements Using Charge Gradient mentioning

confidence: 99%

Anomalous Motion of Charged Domain Walls and Associated Negative Capacitance in Copper–Chlorine Boracite

et al. 2021

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At lower temperatures (≈255 K [1] ), however, the original high-symmetry para electric-orthorhombic state is restored. Symmetry associated with this re-entrant phase transition has unusually, therefore, increased on cooling. Some observations show that this generates a local dip in the heat capacity, [1,2] stalling entropy reduction on decreasing temperature. [1] Strange symmetry transformations also occur in flux-grown barium titanate crystals, where highly ordered "Forsbergh Patterns" can first appear and then subsequently disappear, as temperature is monotonically varied. [3,4] Most recently, heating has been seen to cause high symmetry labyrinthine ferroelectric domain patterns to give way to lower symmetry stripe arrays: an effect classified as an "inverse transition". [5] Clearly, symmetry changes can therefore occasionally occur in the opposite sense to that normally seen. While fundamental thermodynamic laws are not broken, such cases are unusual, arresting, and worthy of note. [6]

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Section: Negative Capacitance and Measurements Using Charge Gradient mentioning

confidence: 99%

Anomalous Motion of Charged Domain Walls and Associated Negative Capacitance in Copper–Chlorine Boracite

et al. 2021

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“…PCA has already proven to be a useful technique for denoising AFM measurements ( e.g. , charge gradient microscopy) and is described in detail in Supporting Information and elsewhere . Briefly, PCA performs a principal axis rotation of the variance–covariance matrix constructed from the original data set.…”

Section: Resultsmentioning

confidence: 99%

Breaking the Time Barrier in Kelvin Probe Force Microscopy: Fast Free Force Reconstruction Using the G-Mode Platform

Collins¹,

Ahmadi

et al. 2017

ACS Nano

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Atomic force microscopy (AFM) offers unparalleled insight into structure and material functionality across nanometer length scales. However, the spatial resolution afforded by the AFM tip is counterpoised by slow detection speeds compared to other common microscopy techniques (e.g., optical, scanning electron microscopy, etc.). In this work, we develop an ultrafast AFM imaging approach allowing direct reconstruction of the tip-sample forces with ∼3 order of magnitude higher time resolution than is achievable using standard AFM detection methods. Fast free force recovery (FR) overcomes the widely viewed temporal bottleneck in AFM, that is, the mechanical bandwidth of the cantilever, enabling time-resolved imaging at sub-bandwidth speeds. We demonstrate quantitative recovery of electrostatic forces with ∼10 μs temporal resolution, free from influences of the cantilever ring-down. We further apply the FR method to Kelvin probe force microscopy (KPFM) measurements. FR-KPFM is an open loop imaging approach (i.e., no bias feedback), allowing ultrafast surface potential measurements (e.g., <20 μs) to be performed at regular KPFM scan speeds. FR-KPFM is demonstrated for exploration of ion migration in organometallic halide perovskite materials and shown to allow spatiotemporal imaging of positively charged ion migration under applied electric field, as well as subsequent formation of accumulated charges at the perovskite/electrode interface. In this work, we demonstrate quantitative FR-KPFM measurements-however, we fully expect the FR approach to be valid for all modes of noncontact AFM operation, including noninvasive probing of ultrafast electrical and magnetic dynamics.

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“…7(b) can be viewed as representing IV characteristics of the photocurrent. Further details on PCA can be found in our recent publication 51 .…”

Section: Discussionmentioning

confidence: 99%

Touching is believing: interrogating halide perovskite solar cells at the nanoscale via scanning probe microscopy

Huang

Esfahani

et al. 2017

npj Quant Mater

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Halide perovskite solar cells based on CH 3 NH 3 PbI 3 and related materials have emerged as the most exciting development in the next generation photovoltaic technologies, yet the microscopic phenomena involving photo-carriers, ionic defects, spontaneous polarization, and molecular vibration and rotation interacting with numerous grains, grain boundaries, and interfaces are still inadequately understood. In fact, there is still need for an effective method to interrogate the local photovoltaic properties of halide perovskite solar cells that can be directly traced to their microstructures on one hand and linked to their device performance on the other hand. In this perspective, we propose that scanning probe microscopy (SPM) techniques have great potential to realize such promises at the nanoscale, and highlight some of the recent progresses and challenges along this line of investigation toward local probing of photocurrent, work function, ionic activities, polarization switching, and chemical degradation. We also emphasize the importance of multi-modality imaging, in-operando scanning, big data analysis, and multidisciplinary collaboration for further studies toward fully understanding of these complex systems.

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Imaging ferroelectric domains via charge gradient microscopy enhanced by principal component analysis

Cited by 7 publications

References 34 publications

Anomalous Motion of Charged Domain Walls and Associated Negative Capacitance in Copper–Chlorine Boracite

Anomalous Motion of Charged Domain Walls and Associated Negative Capacitance in Copper–Chlorine Boracite

Breaking the Time Barrier in Kelvin Probe Force Microscopy: Fast Free Force Reconstruction Using the G-Mode Platform

Touching is believing: interrogating halide perovskite solar cells at the nanoscale via scanning probe microscopy

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