Abstract:When the atomic layers in a non-centrosymmetric van der Waals structure slide against each other, the interfacial charge transfer results in a reversal of the structure’s spontaneous polarization. This phenomenon is known as sliding ferroelectricity and it is markedly different from conventional ferroelectric switching mechanisms relying on ion displacement. Here, we present layer dependence as a new dimension to control sliding ferroelectricity. By fabricating 3 R MoS2 of various thicknesses into dual-gate fi… Show more
“…The effect of trap states can be excluded from the unchanged hysteresis loops windows at different sweep rates (Supplementary Fig. 12 ) since the hysteresis loops windows induced by the trap states usually become larger when slowing down the voltage sweep rate 46 , 47 . Fig.…”
Ferroelectricity in ultrathin two-dimensional (2D) materials has attracted broad interest due to potential applications in nonvolatile memory, nanoelectronics and optoelectronics. However, ferroelectricity is barely explored in materials with native centro or mirror symmetry, especially in the 2D limit. Here, we report the first experimental realization of room-temperature ferroelectricity in van der Waals layered GaSe down to monolayer with mirror symmetric structures, which exhibits strong intercorrelated out-of-plane and in-plane electric polarization. The origin of ferroelectricity in GaSe comes from intralayer sliding of the Se atomic sublayers, which breaks the local structural mirror symmetry and forms dipole moment alignment. Ferroelectric switching is demonstrated in nano devices fabricated with GaSe nanoflakes, which exhibit exotic nonvolatile memory behavior with a high channel current on/off ratio. Our work reveals that intralayer sliding is a new approach to generate ferroelectricity within mirror symmetric monolayer, and offers great opportunity for novel nonvolatile memory devices and optoelectronics applications.
“…The effect of trap states can be excluded from the unchanged hysteresis loops windows at different sweep rates (Supplementary Fig. 12 ) since the hysteresis loops windows induced by the trap states usually become larger when slowing down the voltage sweep rate 46 , 47 . Fig.…”
Ferroelectricity in ultrathin two-dimensional (2D) materials has attracted broad interest due to potential applications in nonvolatile memory, nanoelectronics and optoelectronics. However, ferroelectricity is barely explored in materials with native centro or mirror symmetry, especially in the 2D limit. Here, we report the first experimental realization of room-temperature ferroelectricity in van der Waals layered GaSe down to monolayer with mirror symmetric structures, which exhibits strong intercorrelated out-of-plane and in-plane electric polarization. The origin of ferroelectricity in GaSe comes from intralayer sliding of the Se atomic sublayers, which breaks the local structural mirror symmetry and forms dipole moment alignment. Ferroelectric switching is demonstrated in nano devices fabricated with GaSe nanoflakes, which exhibit exotic nonvolatile memory behavior with a high channel current on/off ratio. Our work reveals that intralayer sliding is a new approach to generate ferroelectricity within mirror symmetric monolayer, and offers great opportunity for novel nonvolatile memory devices and optoelectronics applications.
“…1−6 The intriguing switching mechanism makes sliding ferroelectricity promising for both fundamental research and device application. Benefiting from the weak interlayer dipole coupling, cumulative polarization states can be achieved in sliding ferroelectricity, which have been confirmed by the electrical transport measurement 7 and Kelvin probe force microscopy. 8 In sliding ferroelectrics, the polarization is confined to the interface, while the electric conductivity is provided by the migration of free carriers along the individual layer.…”
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confidence: 62%
“…Sliding ferroelectricity, which originates from the charge transfer between the asymmetric atomic layers in van der Waals materials, has been recently demonstrated. , The out-of-plane polarization can be switched by interlayer translation, distinct from the ion displacement in traditional ferroelectrics. − The intriguing switching mechanism makes sliding ferroelectricity promising for both fundamental research and device application. Benefiting from the weak interlayer dipole coupling, cumulative polarization states can be achieved in sliding ferroelectricity, which have been confirmed by the electrical transport measurement and Kelvin probe force microscopy . In sliding ferroelectrics, the polarization is confined to the interface, while the electric conductivity is provided by the migration of free carriers along the individual layer.…”
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confidence: 70%
“…In sliding ferroelectrics, the polarization is confined to the interface, while the electric conductivity is provided by the migration of free carriers along the individual layer. The decoupling between ferroelectricity and conductivity in sliding ferroelectricity results in an abundance of physical phenomena such as a switchable superconductor, , switchable Moiré potentials, and nonvolatile memory . Such extraordinary physical phenomena associated with switchable electric dipoles exhibit great prospects in novel devices featured with in-memory computing.…”
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confidence: 99%
“…The decoupling between ferroelectricity and conductivity in sliding ferroelectricity results in an abundance of physical phenomena such as a switchable superconductor, 9,10 switchable Moirépotentials, 11 and nonvolatile memory. 7 Such extraordinary physical phenomena associated with switchable electric dipoles exhibit great prospects in novel devices featured with in-memory computing. However, due to the weak polarization, the reported sliding ferroelectric transistors usually show a low on/off ratio, restricting the practical application of the revealed phenomena.…”
Sliding ferroelectricity associated with interlayer translation is an excellent candidate for ferroelectric device miniaturization. However, the weak polarization gives rise to the poor performance of sliding ferroelectric transistors with a low on/off ratio and a narrow memory window, which restricts its practical application. To address the issue, we propose a facile strategy by regulating the Schottky barrier in sliding ferroelectric semiconductor transistors based on γ-InSe, in which a high performance with a large on/off ratio (10 6 ) and a wide memory window (4.5 V) was ultimately acquired. Additionally, the memory window of the device can be further modulated by electrostatic doping or light excitation. These results open up new ways for designing novel ferroelectric devices based on emerging sliding ferroelectricity.
Although the monolayers of most 2D materials are non-ferroelectric with highly symmetric lattices, symmetry breaking may take place in their bilayers upon some stacking configuration, giving rise to so-called sliding ferroelectricity where the vertical polarizations can be electrically reversed via interlayer translation. However, it is not supposed to appear in systems like graphene bilayer with centro-symmetry at any stacking configuration, and the origin of the recently reported ferroelectricity (Nature 2020, 588, 71) in graphene bilayer intercalated between h-BN remains mysterious. Here, a type of across-layer sliding ferroelectricity that arises from the asymmetry of next-neighbor interlayer couplings is proposed. The first-principles evidence is shown that the vertical polarizations in intercalated centro-symmetric 2D materials like graphene bilayer can be switched via multilayer sliding, which is likely to be the origin of the observed ferroelectric hysteresis. Moreover, such ferroelectricity may exist in a series of other heterolayers with quasidegenerate polar states, like graphene bilayer or trilayer on BN substrate, or even with a molecule layer on surface where each molecule can store 1-bit data independently, resolving the bottleneck issue of sliding ferroelectricity for high-density data storage.
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