Epitaxial growth of trilayer graphene moiré superlattice

The graphene-based moiré superlattice has been demonstrated as an exciting system for investigating strong correlation phenomenon. However, the fabrication of such moiré superlattice mainly relies on transfer technology. Here, we report the epitaxial growth of trilayer graphene(TLG) moiré superlattice on hexagonal boron nitride(h BN) by a remote plasma-enhanced chemical vapor deposition method. The as-grown TLG/h BN shows a uniform moiré pattern with a period of ~ 15 nm by atomic force microscopy(AFM) imaging, which agrees with the lattice mismatch between graphene and h BN. By fabricating the device with both top and bottom gates, we observed a gate-tunable bandgap at charge neutral point(CNP) and displacement field tunable satellite resistance peaks at half and full fillings. The resistance peak at half-filling indicates a strong electron–electron correlation in our grown TLG/h BN superlattice. In addition, we observed quantum Hall states at Landau level filling factors ν = 6, 10, 14,..., indicating that our grown trilayer graphene has the ABC stacking order. Our work suggests that epitaxy provides an easy way to fabricate stable and reproducible two-dimensional strongly correlated electronic materials.

Superlubricity enabled dry transfer of non-encapsulated graphene

Transferring high-quality exfoliated graphene flakes onto different substrates while keeping the graphene free of polymer residues is of great importance, but at the same time very challenging. Currently, the only feasible way is the so-called all-dry "pick-and-lift" method, in which a hexagonal boron nitride(hBN) flake is employed to serve as a stamp to pick up graphene from one substrate and to lift it down onto another substrate. The transferred graphene samples, however,are always covered or encapsulated by hBN flakes, which leads to difficulties in further characterizations. Here, we report an improved "pick-and-lift" method, which allows ultra-clean graphene flakes to be transferred onto a variety of substrates without hBN coverage. Basically, by exploiting the superlubricity at the graphene/hBN stack interface, we are able to remove the top-layer hBN stamp by applying a tangential force and expose the underneath graphene.

Dynamic disease manifestations among individuals infected with SARS-CoV-2 Omicron variant

To the Editor:The unprecedented pandemic of coronavirus disease 2019(COVID-19)has put tremendous pressure on healthcare resources and economic development worldwide.Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)Omicron strain has become the dominant causative strain of COVID-19 in most countries since the end of 2021.Although a large cohort study comparing the symptomatic presentation of SARSCoV-2 Omicron and Delta infection has been made in the UK,[1]features and evolution of symptoms of individuals infected with Omicron are rarely reported in other countries or regions,especially among Asian individuals.

Quick identification of ABC trilayer graphene at nanoscale resolution via a near-field optical route

ABC-stacked trilayer graphene has exhibited a variety of correlated phenomena owing to its relatively flat bands and gate-tunable bandgap.However,convenient methods are still lacking for identifying ABC graphene with nanometer-scale resolution.Here we demonstrate that the scanning near-field optical microscope working in ambient conditions can provide quick recognition of ABC trilayer graphene with no ambiguity and excellent resolution(∼20 nm).The recognition is based on the difference in their near-field infrared(IR)responses between the ABA and ABC trilayers.We show that in most frequencies,the response of the ABC trilayer is weaker than the ABA trilayer.However,near the graphene phonon frequency(∼1585 cm−1),ABC’s response increases dramatically when gated and exhibits a narrow and sharp Fano-shape resonant line,whereas the ABA trilayer is largely featherless.Consequently,the IR contrast between ABC and ABA becomes reversed and can even be striking(ABC/ABA∼3)near the graphene phonon frequency.The observed near-field IR features can serve as a golden rule to quickly distinguish ABA and ABC trilayers with no ambiguity,which could largely advance the exploration of correlation physics in ABC-stacked trilayer graphene.

Catalyst-Free Growth of Nanographene Films on Various Substrates

我们开发了一个新方法在各种各样的底层上直接种一致 graphene 电影，例如绝缘体，半导体，甚至金属，没有使用任何催化剂。生长用遥远的血浆改进化学药品蒸汽免职(r-PECVD ) 被执行在相对低的温度的系统，启用 graphene 电影的免职直到 4 英寸的晶片规模。扫描通道显微镜学(STM ) 证实电影由在侧面的尺寸的十纳米的 nanocrystalline graphene 粒子组成。为 nanographene 的生长机制为 PECVD 方法种的钻石类似于那，尽管有在 graphene 的情况中被形成的 sp2 碳原子而非象在钻石的 sp3 碳原子。这条生长途径简单、便宜、可伸缩，并且可能在象薄电影电阻器，煤气的传感器，电极材料，和透明传导性的电影那样的域里有潜在的应用程序。

Guest-Mediated Hierarchical Self-Assembly of Dissymmetric Organic Cages to Form Supramolecular Ferroelectrics Guest-Mediated Hierarchical Self-Assembly of Dissymmetric Organic Cages to Form Supramolecular Ferroelectrics

Herein,we report on the guest-responsive hierarchical self-assembly of dissymmetric cage DC-1 with an intrinsic dipole along its C_(3)-symmetric axis.DC-1 molecules self-assemble into supramolecular columns with themolecular dipoles aligned along the columnar axis.Mediated by different host-guest interactions of ethyl acetate(EtOAc)and chloroform(CHCl_(3)),the columns are arranged in an antiparallel and parallel fashion,respectively,leading to a switch of the centrosym metric and noncentrosymmetric superstructures.The symmetry of themolecular packing of DC-1 molecules of the noncentrosymmetric crystalline phase is therefore broken,producing a supramolecular ferroelectric with second-harmonic generation and piezoelectric responses.We demonstrate that cages can serve as promising building blocks for the discovery of supramolecular materials with emergent functions and properties,including but not limited to,organic ferroelectrics and nonlinear optics.