Characteristic Plasmon Energies for 2D In2Se3 Phase Identification at Nanoscale.

Two-dimensional (2D) materials with competing polymorphs offer remarkable potential to switch the associated 2D functionalities for novel device applications. Probing their phase transition and competition mechanisms requires nanoscale characterization techniques that can sensitively detect the nucleation of secondary phases down to single-layer thickness. Here we demonstrate nanoscale phase identification on 2D In2Se3 polymorphs, utilizing their distinct plasmon energies that can be distinguished by electron energy-loss spectroscopy (EELS). The characteristic plasmon energies of In2Se3 polymorphs have been validated by first-principles calculations, and also been successfully applied to reveal phase transitions using in situ EELS. Correlating with in situ X-ray diffraction, we further derive a subtle difference in the valence electron density of In2Se3 polymorphs, consistent with their disparate electronic properties. The nanometer resolution and independence of orientation make plasmon-energy mapping a versatile technique for nanoscale phase identification on 2D materials.

Atomically Unraveling Highly Crystalline Self-Intercalated Tantalum Sulfide with Correlated Stacking Registry-Dependent Magnetism.

In self-intercalated two-dimensional (ic-2D) materials, understanding the local chemical environment and the topology of the filling site remains elusive, and the subsequent correlation with the macroscopically manifested physical properties has rarely been investigated. Herein, highly crystalline gram-scale ic-2D Ta1.33S2 crystals were successfully grown by the high-pressure high-temperature method. Employing combined atomic-resolution scanning transmission electron microscopy annular dark field imaging and density functional theory calculations, we systematically unveiled the atomic structures of an atlas of stacking registries in a well-defined √3(a) × âˆš3(a) Ta1.33S2 superlattice. Ferromagnetic order was observed in the AC' stacking registry, and it evolves into an antiferromagnetic state in AA/AB/AB' stacking registries; the AA' stacking registry shows ferrimagnetic ordering. Therefore, we present a novel approach for fabricating large-scale highly crystalline ic-2D crystals and shed light on a powerful means of modulating the magnetic order of ic-2D systems via stacking engineering, i.e., stackingtronics.

Epitaxial Growth of Large Area Two-Dimensional Ferroelectric α-In2Se3.

Two-dimensional (2D) ferroelectric materials have attracted intensive attention in recent years for academic research. However, the synthesis of large-scale 2D ferroelectric materials for electronic applications is still challenging. Here, we report the successful synthesis of centimeter-scale ferroelectric In2Se3 films by selenization of In2O3 in a confined space chemical vapor deposition method. The as-grown homogeneous thin film has a uniform thickness of 5 nm with robust out-of-plane ferroelectricity at room temperature. Scanning transmission electron microscopy and Raman spectroscopy reveal that the thin film is 2H stacking α-In2Se3 with excellent crystalline quality. Electronic transport measurements of In2Se3 highlight the current-voltage hysteresis and polarization modulated diode effect due to the switchable Schottky barrier height (SBH). First-principles calculations reveal that the polarization modulated SBH is originated from the competition between interface charge transfer and polarized charge. The large area growth of epitaxial In2Se3 opens up potential applications of In2Se3 in novel nanoelectronics.

Wide-Range and Multistate Work Functions of Organometallic Halide Perovskite Films Regulated by Ferroelectric Substrates.

Work function of organometallic halide perovskite (OHP) films is one of the most crucial photoelectric properties, which dominates the carrier dynamics in OHP-based devices. Despite surface treatments by additives being widely used to promote crystallization and passivate defects in OHP films, these chemical strategies for modulation of work functions face two trade-offs: homogeneity on the surface versus along the thickness; the range versus the accuracy of modulation. Herein, by using ferroelectric substrates of uniform polarization and subnanometer roughness, homogeneous CH3NH3PbI3 films are fabricated with five states of work functions with large spanning (∼0.8 eV) and high precision (sd ∼ 0.01 eV). We reveal that the ferroelectric polarizations and the smooth surfaces regulate CH3NH3+ orientations and suppress distortions of PbI6 octahedrons. The wide-range and multistate work functions originate from the ordered CH3NH3+ orientations and PbI6 octahedrons, which result in intensity enhancements and wavelength shifts in photoluminescence with a 30-fold increase of photoexcited carrier lifetime.

Realizing multiple non-volatile resistance states in a two-dimensional domain wall ferroelectric tunneling junction.

Two-dimensional ferroelectric tunnel junctions (2D FTJs) with an ultrathin van der Waals ferroelectrics sandwiched by two electrodes have great applications in memory and synaptic devices. Domain walls (DWs), formed naturally in ferroelectrics, are being actively explored for their low energy consumption, reconfigurable, and non-volatile multi-resistance characteristics in memory, logic and neuromorphic devices. However, DWs with multiple resistance states in 2D FTJ have rarely been explored and reported. Here, we propose the formation of 2D FTJ with multiple non-volatile resistance states manipulated by neutral DWs in a nanostripe-ordered ß'-In2Se3 monolayer. By combining density functional theory (DFT) calculations with nonequilibrium Green's function method, we found that a large TER ratio can be obtained due to the blocking effect of DWs on the electronic transmission. Multiple conductance states are readily obtained by introducing different numbers of the DWs. This work opens a new route to designing multiple non-volatile resistance states in 2D DW-FTJ.

Giant magnetoresistance and tunneling electroresistance in multiferroic tunnel junctions with 2D ferroelectrics.

Multiferroic tunneling junctions (MFTJs), composed of two magnetic electrodes separated by an ultrathin ferroelectric (FE) thin film as a barrier, have received great attention in multi-functional devices. Recent theoretical and experimental works have revealed that ferroelectric polarization exists at room temperature in two-dimensional ferroelectric (2D FE) materials within the ultrathin thickness. Here we propose a novel MFTJ Ni/bilayer In2Se3/BN/Ni, in which the resistance of the tunneling spin polarization electrons can be modulated by different magnetization alignments of the electrode and electric polarization direction of the 2D FE In2Se3 layer, leading to multiple tunneling resistance states. The tunneling magnetoresistance (TMR) and electroresistance (TER) of MFTJs are enhanced by the inserted h-BN layer, achieving an ON/OFF TER ratio of 4188% as well as a TMR ratio of 581% with a much lower resistance area. The giant tunneling resistance ratio, multiple resistance states, and ultra-low energy consumption in 2D FE-based MFTJs suggest their great potential in non-destructive non-volatile memories.

m(6)A demethylase ALKBH5 inhibits cell proliferation and the metastasis of colorectal cancer by regulating the FOXO3/miR-21/SPRY2 axis.

OBJECTIVE: Colorectal cancer is a common malignancy worldwide. This research aimed to investigate the role of α-ketoglutarate-dependent dioxygenase alkB homologue 5 (ALKBH5), a N6-methyladenosine (m(6)A) demethylase, on the cell proliferation and metastasis of colorectal cancer. METHODS: The interaction relationship between FOXO3, miR-21, and SPRY2 were predicted by starBase 2.0 and determined using RIP, CHIP, and dual-luciferase reporter assays. Quantitative reverse transcription PCR (RT-qPCR) and western blot were used to measure the gene and miRNA expressions of ALKBH5, FOXO3, miR-21, and SPRY2. The cell proliferation was determined using CCK8 and colony formation assays. The metastatic abilities were measured using wound healing and transwell assays. RESULTS: In colorectal cancer, downregulated ALKBH5 is related to poor prognosis. Rescued ALKBH5 suppresses the proliferation and metastasis of colorectal cancer cells. The role of ALKBH5 is achieved by reducing the m(6)A modification of forkhead box O3 (FOXO3), which enhances its stability. FOXO3 targets miR-21 and increases the SPRY2 expressions. The antitumor effects of ALKBH5 can be blocked by FOXO3 knockdown, which is reversed by the miR-21 inhibitor. CONCLUSION: ALKBH5 plays an antitumor role in colorectal cancer by regulating the FOXO3/miR-21/SPRY2 axis, providing a new direction for colorectal cancer therapy.