Publications by authors named "Beituo Liu"
Fundamentally, ferroelectrics must belong to a noncentrosymmetric space group, limiting the exploration of more new ferroelectric materials. We circumvent this limitation by triggering structure distortion and inducing ferroelectricity in centrosymmetric van der Waals group-IV monochalcogenide GeSe semiconductor that features unexpected intrinsic out-of-plane antiferroelectricity. Double-type and single-type hysteresis loops from electric measurements, bonding distortion observed in in-situ atomic imaging, and perpendicular polarization uncovered by first-principles calculations, confirm the intrinsic out-of-plane antiferroelectricity and the antiferroelectric-ferroelectric transition induced by the vertical external electric-field.
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- Exploring the role of valley manipulatable layered semiconductors, particularly in valleytronic devices, is the focus of this research on van der Waals (vdW) ReSe, highlighting its phonon chirality and scattering behavior.
- The study employs various spectroscopic techniques to reveal critical features like the direction of Re chains, chiral phonon existence, and the influence of layer thickness and temperature on valley polarization strength.
- The findings indicate potential advancements in valley physics and the development of valley(opto)tronic nanodevices using low-symmetry vdW ReSe due to its strong phonon-photon coupling and exciton-like effects.
The polymorphic nature of InSe leads to excellent phase-dependent physical properties including ferroelectricity, photoelectricity, and especially the intriguing phase change ability, making the precise phase modulation of InSe of fundamental importance but very challenging. Here, the growth of InSe with desired-phase is realized by temperature-controlled selenization of van der Waals (vdW) layered bulk γ-InSe. Detailed results of Raman spectroscopy, scanning electron microscopy (SEM), and state-of-the-art spherical aberration-corrected transmission electron microscopy (Cs-TEM) clearly and consistently show that β-InSe, 3R α-InSe, and 2H α-InSe can be perfectly obtained at ≈270, ≈300, and ≈600 °C, respectively.
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- Researchers have developed large-area 2D van der Waals (vdW) heterostructures using annealed SnSe, improving the yield and reproducibility over traditional mechanical methods that limit scalability.
- The study employs in situ Raman analyses and advanced transmission electron microscopy to analyze the optimal conditions for forming SnSe layers, resulting in sharp interfaces and specific orientations.
- Additionally, the optical properties of these heterostructures show unique valley polarization characteristics that allow adjustable band alignment, which could lead to innovative applications in photodetection and photovoltaics.
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- Researchers have observed atomic-level interlayer sliding dynamics and polarization reversal in yttrium-doped γ-InSe, a van der Waals layered material.
- The study reveals real-time sliding occurring in a 1/3-unit cell along the armchair direction, facilitated by low-energy electron-beam illumination, indicating low switching barriers.
- The findings introduce a new sliding mechanism and contribute significantly to the understanding of sliding ferroelectrics for applications in non-volatile storage and ferroelectric field-effect transistors.
Ferroic compounds FeO(SeO) (FSO) and Fe(SeO)·3HO (FSOH) prepared by the hydrothermal method are characterized and their optical properties are investigated by combining with first-principles calculations. The results show that (i) FSO is antiferromagnetic below ∼110 K and becomes ferromagnetic at elevated temperatures, while FSOH is antiferromagnetic at low temperatures probably due to a change in the spin state from Fe ( = 5/2) to Fe ( = 2); (ii) the optical bandgap is determined to be ∼2.83 eV for FSO and ∼2.
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