Sliding ferroelectricity in van der Waals layered γ-InSe semiconductor

Abstract

Two-dimensional (2D) van-der-Waals (vdW) layered ferroelectric semiconductors are highly desired for in-memory computing and ferroelectric photovoltaics or detectors. Beneficial from the weak interlayer vdW-force, controlling the structure by interlayer twist/translation or doping is an effective strategy to manipulate the fundamental properties of 2D-vdW semiconductors, which has contributed to the newly-emerging sliding ferroelectricity. Here, we report unconventional room-temperature ferroelectricity, both out-of-plane and in-plane, in vdW-layered γ-InSe semiconductor triggered by yttrium-doping (InSe:Y). We determine an effective piezoelectric constant of ∼7.5 pm/V for InSe:Y flakes with thickness of ∼50 nm, about one order of magnitude larger than earlier reports. We directly visualize the enhanced sliding switchable polarization originating from the fantastic microstructure modifications including the stacking-faults elimination and a subtle rhombohedral distortion due to the intralayer compression and continuous interlayer pre-sliding. Our investigations provide new freedom degrees of structure manipulation for intrinsic properties in 2D-vdW-layered semiconductors to expand ferroelectric candidates for next-generation nanoelectronics.

Across‐Layer Sliding Ferroelectricity in 2D Heterolayers

“…In 2017, we proposed that for most non‐ferroelectric 2D materials, certain stacking of bilayer or multilayer may break the symmetry and give rise to so‐called sliding ferroelectricity, where the vertical polarizations are switchable via in‐plane translation, i.e., interlayer sliding. [ 2 ] Over the next few years, such ferroelectricity have been experimentally detected in bilayer or multilayer BN, [ 3–5 ] transition‐metal dichalcogenides (TMDs) like WTe 2 , [ 6–9 ] MoS 2 , [ 10–16 ] MoTe 2 , [ 17 ] ReS 2 , [ 18 ] InSe [ 19 ] and even multiwall nanotubes, [ 20 ] and amphidynamic crystal. [ 21 ] This mechanism is applicable to most 2D materials except for mono‐element systems like graphene and phosphorene, as the inversion symmetry of their bilayers can always be maintained at any interlayer‐sliding vector.…”

“…transition-metal dichalcogenides (TMDs) like WTe 2 , [6][7][8][9] MoS 2 , [10][11][12][13][14][15][16] MoTe 2 , [17] ReS 2 , [18] InSe [19] and even multiwall nanotubes, [20] and amphidynamic crystal. [21] This mechanism is applicable to most 2D materials except for mono-element systems like graphene and phosphorene, as the inversion symmetry of their bilayers can always be maintained at any interlayersliding vector.…”

High-Performance Sliding Ferroelectric Transistor Based on Schottky Barrier Tuning

“…To address the above drawbacks, a tunable Schottky barrier is introduced in sliding ferroelectric channel transistor (SFeCT), realizing the high performance with a wide memory window and a large on/off ratio. The γ-InSe was selected as a channel material, the ferroelectricity of which has been theoretically predicted. , Besides, it shows high carrier mobility exceeding 10 3 cm 2 V –1 s –1 at room temperature. , We experimentally demonstrated the sliding ferroelectricity in γ-InSe by using graphene as a sensor to monitor the switching of its polarization. The tunable Schottky barrier through electrically modulating the ferroelectric polarization results in a high-performance SFeCT based on γ-InSe, exhibiting a large memory window of 4.5 V and a high on/off ratio of 10 6 .…”

“…The γ-InSe was selected as a channel material, the ferroelectricity of which has been theoretically predicted. 1,13 Besides, it shows high carrier mobility exceeding 10 3 cm 2 V −1 s −1 at room temperature. 14,15 We experimentally demonstrated the sliding ferroelectricity in γ-InSe by using graphene as a sensor to monitor the switching of its polarization.…”

Moiré Synergy: An Emerging Playground by Coupled Moirés

“…The prominent interlayer interactions , make the constituent atomic orbitals interfere constructively to manifest a superlattice of much larger wavelengths than the component lattice parameters, so that the energy band edges significantly flatten in the reciprocal space, nourishing a plethora of exotic quantum phenomena, such as superconductivity, correlated insulators, orbital magnetism, and unusual ferroelectricity . Notably, following the theoretic establishment of 2D ferroelectricity induced by interlayer translation, the experimental demonstrations of sliding ferroelectricity in various 2D stacks have boomed in the past few years. − …”