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PFM characterization and manipulation of ferroelectric domains a–c, Topology image of the crystal plane (010) of CCC (a) and the corresponding vertical PFM amplitude (b) and phase images (c). Inset of b: phase–voltage hysteresis loop and amplitude–voltage butterfly loop. d–f, The electrical switching of the ferroelectric domain: pristine (d), after applying a negative bias voltage (e) and after applying a positive bias voltage (f). The voltage of ±220 V is applied on the central area for 20 s. Scale bars: a–c, 10 μm; d–f, 4.5 μm. Source data
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Sliding ferroelectricity is a recently observed polarity existing in two-dimensional materials. However, due to the weak polarization and poor electrical insulation in these materials, existing experimental evidences are indirect and mostly based on nanoscale transport properties or piezoresponse force microscopy. We report the direct observation o...
Citations
... Indeed, using the Br À ions as the indication, the displacement of Pb 2 + atoms is obviously noticed between the LTP and HTP structures. [34] The transition to the calculated HTP structure leads to a reduction in the lattice energy and achieves the most thermodynamically stable structure when the Pb 2 + centers in each SBU are in orderly alignment along the c-axis. Further displacing Pb 2 + atoms beyond this optimal level is not energetically favorable (Figure 5e). ...
Lead halide molecular ferroelectrics represent an important class of luminescent ferroelectrics, distinguished by their high chemical and structural tunability, excellent processability and distinctive luminescent characteristics. However, their inherent instability, prone to decomposition upon exposure to moisture and light, hinders their broader ferroelectric applications. Herein, for the first time, we present a series of isoreticular metal–organic framework (MOF)‐type lead halide luminescent ferroelectrics, demonstrating exceptional robustness under ambient conditions for at least 15 months and even when subjected to aqueous boiling conditions. Unlike conventional metal‐oxo secondary building units (SBUs) in MOFs adopting highly centrosymmetric structure with limited structural distortion, our lead halide‐based MOFs occupy structurally deformable [Pb2X]⁺ (X=Cl⁻/Br⁻/I⁻) SBUs that facilitate a c‐axis‐biased displacement of Pb²⁺ centers and substantially contribute to thermoinducible structural transformation. Importantly, this class of MOF‐type lead halide ferroelectrics undergo ferroelectric‐to‐paraelectric phase transitions with remarkably high Curie temperature of up to 505 K, superior to most of molecular ferroelectrics. Moreover, the covalent bonding between phosphorescent organic component and the light‐harvesting inorganic component achieves efficient spin‐orbit coupling and intersystem crossing, resulting in long‐lived afterglow emission. The compelling combination of high stability, ferroelectricity and afterglow emission exhibited by lead halide MOFs opens up many potential opportunities in energy‐conversion applications.
... Additionally, in the realm of nonvolatile layertronics devices, intrinsic electric polarization in QALHE materials is required to break the PT symmetry, in order to render a detectable anomalous Hall conductance. It has been demonstrated that the interlayer interaction in Van der Waals (vdW) materials can induce intrinsic out-of-plane electric polarization whose orientation can be dynamically reversed by interlay sliding (known as sliding ferroelectricity) [33][34][35][36][37][38][39][40] . This inherent capability effectively enables the switch of layer-polarized net anomalous Hall conductance between different layers [41][42][43] . ...
Layer Hall effect (LHE), initially discovered in the magnetic topological insulator MnBi 2 Te 4 film, expands the Hall effect family and opens a promising avenue for layertronics applications. In this study, we present an innovative ferroelectric bilayer model to attain a tunable quantum anomalous layer Hall effect (QALHE). This model comprises two ferromagnetic orbital-active Dirac monolayers stacked antiferromagnetically, accompanied by out-of-plane electric polarization. The interplay between the layer-locked Berry curvature monopoles and the intrinsic out-of-plane electric polarization leads to layer-polarized near-quantized anomalous Hall conductance. Using first-principles calculations, we have identified a promising material for this model, namely FeS bilayer. Our calculations demonstrate that the intrinsic out-of-plane electric polarization in the Bernal-stacked FeS bilayer can induce QALHE by regulating the layer-locked Berry curvature of FeS monolayers. Importantly, the intrinsic electric field can be reversed through interlayer sliding. The discovery of ferroelectrically modulated QALHE paves the way for the integrability and non-volatility of layertronics, offering exciting prospects for future applications.
... However, as thickness diminishes, both long-range ferromagnetic and ferroelectric orders tend to be suppressed by mechanisms such as thermal fluctuations and depolarization fields. The realization of either 2D ferromagnetic [16][17][18] or ferroelectric [19][20][21][22][23][24][25][26][27] materials at the single-layer (1L) limit has been reported relatively recently, and these often come with notably reduced transition temperatures. ...
Multiferroic materials, which simultaneously exhibit ferroelectricity and magnetism, have attracted substantial attention due to their fascinating physical properties and potential technological applications. With the trends towards device miniaturization, there is an increasing demand for the persistence of multiferroicity in single-layer materials at elevated temperatures. Here, we report high-temperature multiferroicity in single-layer CuCrSe$_2$, which hosts room-temperature ferroelectricity and 120 K ferromagnetism. Notably, the ferromagnetic coupling in single-layer CuCrSe$_2$ is enhanced by the ferroelectricity-induced orbital shift of Cr atoms, which is distinct from both types I and II multiferroicity. These findings are supported by a combination of second-harmonic generation, piezo-response force microscopy, scanning transmission electron microscopy, magnetic, and Hall measurements. Our research provides not only an exemplary platform for delving into intrinsic magnetoelectric interactions at the single-layer limit but also sheds light on potential development of electronic and spintronic devices utilizing two-dimensional multiferroics.
... However, there is a relative lack of research on the ferroelectric properties 2 of 10 of nonfibrillar proteins [16,17]. Lysozyme, a widely studied globular protein, has a noncentrosymmetric structure, satisfying the basic premise of piezoelectricity [8,18], while the most common tetragonal form of lysozyme crystals (P422) are nonpolar and lack ferroelectricity, making them an ideal model to check whether C 60 doping can transform non-ferroelectric P422 tetragonal lysozyme crystals into ferroelectric ones. ...
The inherent nonpolarity of tetragonal lysozyme crystals excludes a ferroelectricity response. Herein, we present a demonstration of achieving measurable ferroelectricity in tetragonal lysozyme crystals through C60 doping. Ferroelectric characterizations revealed that C60-doped tetragonal lysozyme crystals exhibited typical characteristic ferroelectric hysteresis loops. Crystallographic structural analysis suggested that C60 doping may induce a reduction in the overall symmetry of tetragonal Lys@C60, leading to the observed ferroelectricity response. Moreover, the introduction of C60 facilitates efficient electron transport inside the crystal and influences the polarization of Lys@C60, further contributing to the observed ferroelectricity response. This work verifies that C60 doping can serve as a simple strategy to bestow novel ferroelectric properties to non-ferroelectric lysozyme crystals, potentially rendering them suitable for biocompatible and biodegradable application in implantable and wearable bioelectronics.
... A number of 2D ferroelectric materials, including single-layer γ-AlOOH [8], 3R-MoS 2 [9] and MXene structure Sc 2 CO 2 [10], have been proposed. Among them, sliding ferroelectricity where the vertical electric polarization is switchable through in-plane interlayer sliding has been theoretically proposed [11] and experimentally confirmed in a series of 2D materials such as WTe 2 [12], BN [13,14], ReS 2 [15], a family of WSe 2 /MoSe 2 /WS 2 / MoS 2 [16] and amphidynamic crystal of (15-crown-5)Cd 3 C l6 [17]. Sliding ferroelectricity provides a new route towards multiferroics by combining sliding ferroelectrics with inherent magnetic ordering in 2D materials [3,18,19]. ...
Here, we demonstrate the existence of magnetic ordering and sliding ferroelectricity in two-dimensional CoH2SeO4 multilayers. The experimental result reveals the antiferromagnetic order in powder sample, and first-principles calculation indicates the antiferromagnetic ground state with TN≈75 K in CoH2SeO4 single layer. The sliding ferroelectricity with an asymmetric triplet potential well is theoretically predicted and experimentally confirmed by 180°-piezoelectric hysteresis loops, switchable domains and second harmonic generation signals in CoH2SeO4 multilayers. The vertically stacked ferroelectric capacitor shows both polarization and capacitance hysteresis loops. A ferroelectric transition temperature of ~370 K is obtained from the temperature-dependent dielectricity. The emergence of sliding ferroelectricity and anti-ferromagnetism points out a new route for obtaining low-dimensional multiferroic materials.
... Recently, 2D materials have experienced flourishing development and the stacking of them, e.g., bilayers, is found to be an effective handle to manipulate physical properties. For example, twisted bilayers exhibit diverse electronic properties [35] and sliding bilayers can create ferroelectricity [36][37][38][39][40][41][42][43][44][45][46][47]. Moreover, a theory of bilayer stacking ferroelectricity was proposed in our recent study [42], which summarizes general rules of the creation and annihilation of symmetries using stacking degree of freedom. ...
... The required stacking operations for achieving valley polarizations in all square and hexagonal lattices are listed in Tables S1 and S2 of the SM, respectively. Note that the operations to create bilayers include original stackings (direct stacking, rotation, mirror, etc.; see Tables S1 and S2) and sliding, where the BSFV with direct stacking and sliding is termed as sliding ferrovalley, analogous to sliding ferroelectricity [36][37][38][39][40][41][42][43][44][45][46][47]. As we will see, such BSFV strategy leads to many ferrovalley candidates. ...
Ferrovalley, which refers to the valley polarization being nonvolatile and switchable, is highly desired for valleytronics applications but remains challenging due to rare candidate materials. Here we propose a strategy to realize ferrovalley with bilayer stacking (BSFV) in many candidate systems. As a special case of BSFV, sliding ferrovalley corresponds to the bilayers obtained by a direct AA stacking and subsequent in-plane sliding. Different from previous approaches, the BSFV strategy not only maintains time-reversal symmetry, but also keeps spatial-inversion symmetry in many cases. Importantly, switching of the valley polarization can be easily achieved by interlayer sliding. Group theory analysis is systematically performed over all kinds of lattices to identify those that can host BSFV. High-throughput screening is carried out and leads to 14 BSFV candidates with direct bandgap and 338 with indirect bandgap. First-principles verification of BSFV indicates that the valley polarization can be realized in, e.g., (i) the hexagonal RhCl3 bilayer with a threefold rotation symmetry and 39 meV energy difference among valleys, and (ii) the square-latticed InI bilayer with a fourfold rotation symmetry and 326 meV energy difference among valleys. The presently proposed BSFV strategy offers a highly convenient approach for the realization of polarizers and the advancement of valleytronics applications.
... Organic-inorganic hybrid components are also prone to structural phase transition under thermal stimulation, [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] which can affect their emission intensity and even lead to a PL quenching phenomenon. 28,40 As of present, plentiful photoluminescent OIMHs involve PL decay phenomena during phase transitions, such as [(CH 3 ) 3 NCH 2 CH 3 ] 2 MnCl 4 , 41 (2methylimidazolium)MnCl 3 (H 2 O), 42 and [(CH 3 ) 3 PCH 2 OCH 3 ][PbBr 3 ], 43 among others. ...
Organic-inorganic metal halides (OIMHs) possessing switchable optical and electrical properties holds significant promise for applications in multifunctional sensors, switching devices, and information storage. However, the challenge lies in achieving effective...
... Organic-inorganic hybrid perovskites have been the focus of research in the fields of chips, photovoltaics, and batteries due to their good mechanical reversibility, long carrier transport distance, and high structural flexibility [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . Recently, the ferroelasticity of the popular hybrid semiconductor CH 3 NH 3 PbI 3 has been demonstrated to be beneficial for the improvement of photovoltaic efficiency 19 , while the ferroelastic domain wall facilitates benign carrier transport, thus giving rise to extensive research on ferroelastic semiconductors [20][21][22] . ...
Ferroelastic semiconductor materials have garnered significant research interest due to their promising applications in the fields of shape memory, superelasticity, templated electronic nanostructures, mechanical switching, and optoelectronic transmission. However, the...
... An out-of-plane polarization can originate from the net charge transfer across the vdW interface as the inversion symmetry of the vdW material is broken [13][14][15] . This property has been experimentally demonstrated in rhombohedral-stacked (3R) transition metal dichalcogenides (TMDs) 16,17 and amphidynamic polymers 18 . However, investigations of sliding ferroelectricity have relied on scanning-probe-based techniques and localized measurements, and the device performance of sliding-ferroelectricity-based Fe-FETs has remained unclear. ...
To develop low-power, non-volatile computing-in-memory device using ferroelectric transistor technologies, ferroelectric channel materials with scaled thicknesses are required. Two-dimensional semiconductors, such as molybdenum disulfide (MoS2), equipped with sliding ferroelectricity could provide an answer. However, achieving switchable electric polarization in epitaxial MoS2 remains challenging due to the absence of mobile domain boundaries. Here we show that polarity-switchable epitaxial rhombohedral-stacked (3R) MoS2 can be used as a ferroelectric channel in ferroelectric memory transistors. We show that a shear transformation can spontaneously occur in 3R MoS2 epilayers, producing heterostructures with stable ferroelectric domains embedded in a highly dislocated and unstable non-ferroelectric matrix. This diffusionless phase transformation process produces mobile screw dislocations that enable collective polarity control of 3R MoS2 via an electric field. Polarization–electric-field measurements reveal a switching field of 0.036 V nm⁻¹ for shear-transformed 3R MoS2. Our sliding ferroelectric transistors are non-volatile memory units with thicknesses of only two atomic layers and exhibit an average memory window of 7 V with an applied voltage of 10 V, retention times greater than 10⁴ seconds and endurance greater than 10⁴ cycles.
... It has been demonstrated that the interlayer interaction in Van der Waals (vdW) materials can induce intrinsic out-of-plane electric polarization whose orientation can be dynamically reversed by interlay sliding (known as sliding ferroelectricity). [33][34][35][36][37][38][39][40] This inherent capability effectively enables the switch of layer-polarized net anomalous Hall conductance between different layers. [41][42][43] Therefore, investigating the intrinsic QALHE in ferroelectrically stacked 2D QAHI bilayers would offer signi cant prospects for non-volatile layertronics applications. ...
Layer Hall effect (LHE) initially discovered in the magnetic topological insulator MnBi 2 Te 4 film expands the Hall effect family and opens a promising avenue for layertronics applications. In this study, we present an innovative ferroelectric bilayer model to attain a tunable quantum anomalous layer Hall effect (QALHE). This model comprises two ferromagnetic orbital-active Dirac monolayers stacked antiferromagnetically, accompanied by out-of-plane electric polarization. The interplay between the layer-locked Berry curvature and the intrinsic out-of-plane electric polarization leads to layer-polarized near-quantized anomalous Hall conductance. Using first-principles calculations, we have identified a promising material for this model, namely FeS bilayer. Our calculations demonstrate that the intrinsic out-of-plane electric polarization in the Bernal-stacked FeS bilayer can induce QALHE by regulating the layer-locked Berry curvature of FeS monolayers. Importantly, the intrinsic electric filed can be reversed through interlayer sliding. The discovery of ferroelectrically modulated QALHE paves the way for the integrability and non-volatility of layertronics, offering exciting prospects for future applications.
