Tunable quadruple-well ferroelectric van der Waals crystals

Brehm, John A.; Neumayer, Sabine M.; Lei, Tao; O’Hara, Andrew; Chyasnavichus, Marius; Susner, Michael A.; McGuire, Michael A.; Kalinin, Sergei V.; Jesse, Stephen; Ganesh, Panchapakesan; Pantelides, Sokrates T.; Maksymovych, Petro; Balke, Nina

doi:10.1038/s41563-019-0532-z

Cited by 190 publications

(218 citation statements)

References 51 publications

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“…The sulfur 6 , 7 and selenium 8 – 10 compounds have similar structure of individual layers and a concomitant ferrielectric (FE) ordering, with Cu + and In 3+ ions counter-displaced within individual layers, against the backbone of P 2 Q 4- 6 anions. The spontaneous polarization of the sulfide can range from ~5 μC/cm 2 to ~12 μC/cm2 11 vs ~2.5 μC/cm 2 12 in the selenide, in part due to larger off-centric Cu displacement in the sulfide. Despite the structural similarity, the reported properties of their phase transitions are quite different 10 .…”

Section: Introductionmentioning

confidence: 99%

Piezoelectric domain walls in van der Waals antiferroelectric CuInP2Se6

et al. 2020

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Polar van der Waals chalcogenophosphates exhibit unique properties, such as negative electrostriction and multi-well ferrielectricity, and enable combining dielectric and 2D electronic materials. Using low temperature piezoresponse force microscopy, we revealed coexistence of piezoelectric and non-piezoelectric phases in CuInP 2 Se 6 , forming unusual domain walls with enhanced piezoelectric response. From systematic imaging experiments we have inferred the formation of a partially polarized antiferroelectric state, with inclusions of structurally distinct ferrielectric domains enclosed by the corresponding phase boundaries. The assignment is strongly supported by optical spectroscopies and density-functionaltheory calculations. Enhanced piezoresponse at the ferrielectric/antiferroelectric phase boundary and the ability to manipulate this entity with electric field on the nanoscale expand the existing phenomenology of functional domain walls. At the same time, phase-coexistence in chalcogenophosphates may lead to rational strategies for incorporation of ferroic functionality into van der Waals heterostructures, with stronger resilience toward detrimental size-effects.

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Section: Introductionmentioning

confidence: 99%

Piezoelectric domain walls in van der Waals antiferroelectric CuInP2Se6

et al. 2020

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“…[26,27] Recently, density functional theory (DFT) demonstrated the presence of two iso-symmetric polar phases. [28] When the Cu ions reside within the layers, the predicted polarization is ≈5 μC cm −2 (termed the low polarization or LP phase) whereas if Cu occupies sites within the vdW gaps, the spontaneous polarization is predicted to double to ≈11 μC cm −2 (termed the high polarization or HP phase). Both phases are aligned either parallel (+) or antiparallel (−) to z, resulting in a quadruple-well energy potential as a function of Cu z displacement instead of the usual double-well potential.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the material also exhibits giant negative electrostrictive coefficients, [24,29] which is a direct consequence of the highly anharmonic potential well. [28] In addition, CIPS has a high Cu-ion conductivity that extends into the temperature range of the ferroelectric phase. [30][31][32] It has been shown that in-plane ionic currents can be used to manipulate ferroelectric polarization.…”

Section: Introductionmentioning

confidence: 99%

The Concept of Negative Capacitance in Ionically Conductive Van der Waals Ferroelectrics

Neumayer

Lei

O’Hara

et al. 2020

Advanced Energy Materials

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Negative capacitance (NC) provides a path to overcome the Boltzmann limit that dictates operating voltages in transistors and, therefore, may open up a path to the challenging proposition of lowering energy consumption and waste heat in nanoelectronic integrated circuits. Typically, NC effects in ferroelectric materials are based on either stabilizing a zero‐polarization state or slowing down ferroelectric switching in order to access NC regimes of the free‐energy distribution. Here, a fundamentally different mechanism for NC, based on CuInP2S6, a van der Waals layered ferrielectric, is demonstrated. Using density functional theory and piezoresponse force microscopy, it is shown that an unusual combination of high Cu‐ion mobility and its crucial role in determining polarization magnitude and orientation (P) leads to a negative slope of the polarization versus the electric field E, dP/dE < 0, which is a requirement for NC. This mechanism for NC is likely to occur in a wide class of materials, offering new possibilities for NC‐based devices. The nanoscale demonstration of this mechanism can be extended to the device‐level by increasing the regions of homogeneous polarization and polarization switching, for example, through strain engineering and carefully selected electric field pulses.

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“…Recently CuInP 2 S 6 (CIPS), a typical room-temperature van der Waals (vdW) layered ferroelectric crystal 19,20,21 , has attracted intensive attention due to its unexpected features including giant negative piezoelectricity 22 , tunable quadruple-well ferroelectric nature 23 , negative capacitance characteristic 24 and the interplay between ferroelectricity and ionic conductivity 25,26,27 . These unique characteristics not only bring new insights into the fundamental research 28,29 , but also provide new opportunities for diverse applications of layered ferroelectrics 30,31 .…”

Section: Introductionmentioning

confidence: 99%

Ion adsorption-induced reversible polarization switching of a van der Waals layered ferroelectric

et al. 2020

Preprint

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Solid-liquid interface is a key concept of many research fields, enabling numerous physical phenomena and practical applications. For example, electrode-electrolyte interfaces with electric double layers have been widely used in energy storage and regulating physical properties of functional materials. Creating a specific interface allows emergent functionalities and effects. Here, we show the artificial control of ferroelectric-liquid interfacial structures to switch polarization states reversibly in a van der Waals layered ferroelectric CuInP2S6. We discover that upward and downward polarization states can be induced by spontaneous physical adsorption of anions [DDBS] and cations [DEME], respectively, at the ferroelectric-liquid interface. This distinctive approach circumvents the structural damage of CIPS caused by Cu-ion conductivity during electrical switching process. Moreover, the polarized state features super-long retention time (> 1 year). The interplay between ferroelectric dipoles and adsorbed organic ions has been studied systematically by comparative experiments and first-principles calculations. Such ion adsorption-induced reversible polarization switching in a van der Waals ferroelectric enriches the functionalities of solid-liquid interfaces, offering opportunities for liquid-controlled two-dimensional ferroelectric-based devices.

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Tunable quadruple-well ferroelectric van der Waals crystals

Cited by 190 publications

References 51 publications

Piezoelectric domain walls in van der Waals antiferroelectric CuInP2Se6

Piezoelectric domain walls in van der Waals antiferroelectric CuInP2Se6

The Concept of Negative Capacitance in Ionically Conductive Van der Waals Ferroelectrics

Ion adsorption-induced reversible polarization switching of a van der Waals layered ferroelectric

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