Self-Toughened 2D Moiré Superlattice Membranes with Extreme Thermal Shock Tolerance.

Excellent mechanical strength and toughness are demanded for two-dimensional material (2DM) membranes in various applications to withstand extreme strain and temperature changes and resist crack propagation. However, the trade-off between strength and toughness poses significant challenges in meeting these requirements. This study presents a self-toughened 2D moiré superlattice membrane composed of vertically stacked hexagonal boron nitride and graphene (hBN/Gr) that exhibits high mechanical strength.

Nonadiabatic Renormalization of the Phonon Dispersion in Monolayer and Bilayer Graphene.

Nonadiabatic effects profoundly influence lattice dynamics, resulting in phonon renormalizations not only at the center of Brillouin zone (BZ), but also across the entire dispersion at finite momenta. These nonadiabatic phenomena exhibit clear dimensional dependencies and remain largely unexplored experimentally in low-dimensional systems. Here, we utilize high-resolution electron energy loss spectroscopy to investigate nonadiabatic phonon dispersion renormalization in monolayer graphene (MLG) and Bernal bilayer graphene (BLG).

A novel high endurance HZO FeFET with monolayer graphene inserted in the gate oxide.

The poor endurance of hafnium oxide (HfO)-based ferroelectric field-effect transistors (FeFETs) limits their applications. From a novel perspective of ferroelectric domain engineering, we propose and fabricate a high endurance HfO-based FeFET with monolayer graphene (GR) inserted in the gate oxide for the first time. The introduction of GR between the ferroelectric (FE) layer and the interfacial layer (IL) increases the number of domains in the ferroelectric (FE) layer and reduces the electric field of the IL.

Optical anisotropy of BiSeO and near-field characterization of its waveguide modes.

Anisotropic van der Waals (vdW) materials have attracted increasing attention in nanophotonics due to their unique optical properties. As a stable vdW material with a high dielectric constant () and a wide bandgap, BiSeO shows significant potential for semiconductor applications, but its optical properties have not been extensively studied. In this work, we first measured the refractive index of BiSeO using an imaging spectroscopic ellipsometer and revealed its in-plane and out-of-plane anisotropy.

Edge-feeding synchronous epitaxy of layer-controlled graphene films on heterogeneous catalytic substrates.

Compared with single-layer two-dimensional (2D) materials, bilayer, trilayer, and few-layer 2D materials exhibit enhanced band structure tunability, improved electrical and thermal properties, and superior mechanical strength and barrier performance. However, the layer-controlled synthesis of 2D films with high layer number uniformity remains challenging, due to the difficulty in the additional layer nucleation and the effective realization of layer-by-layer growth. Herein, we report an edge-feeding synchronous epitaxial growth mode breaking the limit of traditional epitaxy theories.

Direct Ice Splitting into H and O Enabled by High Ionic Conductivity.

The molecular splitting of HO is fundamentally significant in energy conversion and storage. While liquid water splitting has achieved scientific and engineering success, the decomposition of solid-state ice has yet to be realized. Here we demonstrate that ice can be directly split at temperatures as low as -40 °C.

Two-dimensional BiSeO and Its Native Insulators for Next-Generation Nanoelectronics.

Silicon's dominance in integrated circuits is largely due to its stable native oxide, SiO, known for its insulating properties and excellent interface to the Si channel. However, silicon-based FETs face significant challenges when further scaled, which inspires the search for better semiconductors. While 2D materials such as MoS, WSe, BP, and InSe are promising, they lack a stable and compatible native oxide.

Low-power 2D gate-all-around logics via epitaxial monolithic 3D integration.

Innovations in device architectures and materials promote transistor miniaturization for improved performance, energy efficiency and integration density. At foreseeable ångström nodes, a gate-all-around (GAA) field-effect transistor based on two-dimensional (2D) semiconductors would provide excellent electrostatic gate controllability to achieve ultimate power scaling and performance delivering. However, a major roadblock lies in the scalable integration of 2D GAA heterostructures with atomically smooth and conformal interfaces.

Cyclododecane-based high-intactness and clean transfer method for fabricating suspended two-dimensional materials.

The high-intactness and ultraclean fabrication of suspended 2D materials has always been a challenge due to their atomically thin nature. Here, we present a universal polymer-free transfer approach for fabricating suspended 2D materials by using volatile micro-molecule cyclododecane as the transfer medium, thus ensuring the ultraclean and intact surface of suspended 2D materials. For the fabricated monolayer suspended graphene, the intactness reaches 99% for size below 10 µm and suspended size reaches 36 µm.

Ultraflat single-crystal hexagonal boron nitride for wafer-scale integration of a 2D-compatible high-κ metal gate.

Hexagonal boron nitride (hBN) has emerged as a promising protection layer for dielectric integration in the next-generation large-scale integrated electronics. Although numerous efforts have been devoted to growing single-crystal hBN film, wafer-scale ultraflat hBN has still not been achieved. Here, we report the epitaxial growth of 4 in.

Even-integer quantum Hall effect in an oxide caused by a hidden Rashba effect.

In the presence of a high magnetic field, quantum Hall systems usually host both even- and odd-integer quantized states because of lifted band degeneracies. Selective control of these quantized states is challenging but essential to understand the exotic ground states and manipulate the spin textures. Here we demonstrate the quantum Hall effect in BiOSe thin films.

Epitaxial Integration of Transferable High-κ Dielectric and 2D Semiconductor.

The synthesis of high-dielectric-constant (high-κ) dielectric materials and their integration with channel materials have been the key challenges in the state-of-the-art transistor architecture, as they can provide strong gate control and low operating voltage. For next-generation electronics, high-mobility two-dimensional (2D) layered semiconductors with dangling-bond-free surfaces and an atomic-thick thickness are being explored as channel materials to achieve shorter channel lengths and less interfacial scattering. Nowadays, the integration of high-κ dielectrics with high-mobility 2D semiconductors mainly relies on atomic layer deposition or transfer stacking, which may cause several undesirable problems, such as channel damage and interface traps.

A Resonance-Sensitive Ultralow-Frequency Raman Mode in Twisted Bilayer Graphene.

Twisted bilayer graphene (tBLG) possesses intriguing physical properties including unconventional superconductivity, enhanced light-matter interaction due to the formation of van Hove singularities (vHS), and a divergence of density of states in the electronic band structures. The vHS energy band gap provides optical resonant transition channels that can be tuned by the twist angle and interlayer coupling. Raman spectroscopy provides rich information on the vHS structure of tBLG.

Polyacrylonitrile as an Efficient Transfer Medium for Wafer-Scale Transfer of Graphene.

The disparity between growth substrates and application-specific substrates can be mediated by reliable graphene transfer, the lack of which currently strongly hinders the graphene applications. Conventionally, the removal of soft polymers, that support the graphene during the transfer, would contaminate graphene surface, produce cracks, and leave unprotected graphene surface sensitive to airborne contaminations. In this work, it is found that polyacrylonitrile (PAN) can function as polymer medium for transferring wafer-size graphene, and encapsulating layer to deliver high-performance graphene devices.

Integrated 2D multi-fin field-effect transistors.

Vertical semiconducting fins integrated with high-κ oxide dielectrics have been at the centre of the key device architecture that has promoted advanced transistor scaling during the last decades. Single-fin channels based on two-dimensional (2D) semiconductors are expected to offer unique advantages in achieving sub-1 nm fin-width and atomically flat interfaces, resulting in superior performance and potentially high-density integration. However, multi-fin structures integrated with high-κ dielectrics are commonly required to achieve higher electrical performance and integration density.

Tuning the Flat Band in BiOSe by Pressure to Induce Superconductivity.

The discovery of superconductivity in twisted bilayer graphene has reignited enthusiasm in the field of flat-band superconductivity. However, important challenges remain, such as constructing a flat-band structure and inducing a superconducting state in materials. Here, we successfully achieved superconductivity in BiOSe by pressure-tuning the flat-band electronic structure.

Observation of the nonanalytic behavior of optical phonons in monolayer hexagonal boron nitride.

Phonon splitting of the longitudinal and transverse optical modes (LO-TO splitting), a ubiquitous phenomenon in three-dimensional polar materials, will break down in two-dimensional (2D) polar systems. Theoretical predictions propose that the LO phonon in 2D polar monolayers becomes degenerate with the TO phonon, displaying a distinctive "V-shaped" nonanalytic behavior near the center of the Brillouin zone. However, the full experimental verification of these nonanalytic behaviors has been lacking.

Graphene sandwich-based biological specimen preparation for cryo-EM analysis.

High-quality specimen preparation plays a crucial role in cryo-electron microscopy (cryo-EM) structural analysis. In this study, we have developed a reliable and convenient technique called the graphene sandwich method for preparing cryo-EM specimens. This method involves using two layers of graphene films that enclose macromolecules on both sides, allowing for an appropriate ice thickness for cryo-EM analysis.