Controlled growth of high-quality graphene is still the bottleneck of practical applications. The widely used chemical vapour deposition process generally suffers from an uncontrollable carbon precipitation effect that leads to inhomogeneous growth and strong correlation to the growth conditions. Here we report the rational design of a binary metal alloy that effectively suppresses the carbon precipitation process and activates a self-limited growth mechanism for homogeneous monolayer graphene. As demonstrated by an ni-mo alloy, the designed binary alloy contains an active catalyst component for carbon source decomposition and graphene growth and a black hole counterpart for trapping the dissolved carbons and forming stable metal carbides. This type of process engineering has been used to grow strictly singlelayer graphene with 100% surface coverage and excellent tolerance to variations in growth conditions. With simplicity, scalability and a very large growth window, the presented approach may facilitate graphene research and industrial applications.

Impurities produced during the synthesis process of a material pose detrimental impacts upon the intrinsic properties and device performances of the as-obtained product. This effect is especially pronounced in graphene, where surface contamination has long been a critical, unresolved issue, given graphene’s two-dimensionality. Here we report the origins of surface contamination of graphene, which is primarily rooted in chemical vapour deposition production at elevated temperatures, rather than during transfer and storage. In turn, we demonstrate a design of Cu substrate architecture towards the scalable production of super-clean graphene (>99% clean regions). The readily available, super-clean graphene sheets contribute to an enhancement in the optical transparency and thermal conductivity, an exceptionally lower-level of electrical contact resistance and intrinsically hydrophilic nature. This work not only opens up frontiers for graphene growth but also provides exciting opportunities for the utilization of as-obtained super-clean graphene films for advanced applications.

Engineering heteroatoms that precisely positioned in covalent triazine frameworks (CTFs) can dramatically enhance the photocatalytic hydrogen evolution rate of CTFs and is thus an effective strategy to improve the photocatalysis performance for porous organic polymers (POPs).

We examine the role of strong nonlinearity on the topologically robust edge state in a one-dimensional system. We consider a chain inspired from the Su-Schrieffer-Heeger model but with a finite-frequency edge state and the dynamics governed by second-order differential equations. We introduce a cubic onsite nonlinearity and study this nonlinear effect on the edge state's frequency and linear stability. Nonlinear continuation reveals that the edge state loses its typical shape enforced by the chiral symmetry and becomes generally unstable due to various types of instabilities that we analyze using a combination of spectral stability and Krein signature analysis. This results in an initially excited nonlinear-edge state shedding its energy into the bulk over a long time. However, the stability trends differ both qualitatively and quantitatively when softening and stiffening types of nonlinearity are considered. In the latter, we find a frequency regime where nonlinear edge states can be linearly stable. This enables high-amplitude edge states to remain spatially localized without shedding their energy, a feature that we have confirmed via long-time dynamical simulations. Finally, we examine the robustness of frequency and stability of nonlinear edge states against disorder, and find that those are more robust under a chiral disorder compared to a nonchiral disorder. Moreover, the frequency-regime where high-amplitude edge states were found to be linearly stable remains intact in the presence of a small amount of disorder of both types.

High-performance graphene field-effect transistors (G-FETs) are fabricated with carrier mobility of up to 5400 cm(2)/V·s and top-gate efficiency of up to 120 (relative to that of back gate with 285 nm SiO(2)) simultaneously through growing high-quality Y(2)O(3) gate oxide at high oxidizing temperature. The transconductance normalized by dimension and drain voltage is found to reach 7900 μF/V·s, which is among the largest of the published graphene FETs. In an as-fabricated graphene FET with a gate length of 310 nm, a peak transconductance of 0.69 mS/μm is realized, but further improvement is seriously hindered by large series resistance. Benefiting from highly efficient gate control over the graphene channel, the Dirac point voltage of the graphene FETs is shown to be designable via simply selecting a gate metal with an appropriate work function. It is demonstrated that the Dirac point voltage of the graphene FETs can be adjusted from negative to positive, respectively, via changing the gate material from Ti to Pd.

High‐quality perovskite single crystals with large size are highly desirable for the fundamental research and high energy detection application. Here, a simple and convenient solution method, featuring continuous‐mass transport process (CMTP) by a steady self‐supply way, is shown to keep the growth of semiconductor single crystals continuously stable at a constant growth rate until an expected crystal size is achieved. A significantly reduced full width at half‐maximum (36 arcsec) of the (400) plane from the X‐ray rocking curve indicates a low angular dislocation of 6.8 × 106 cm−2 and hence a higher crystalline quality for the CH3NH3PbI3(MAPbI3) single crystals grown by CMTP as compared to the conventional inverse temperature crystallization (ITC) method. Furthermore, the CMTP‐based single crystals have lower trap density, reduced by nearly 200% to 4.5 × 109 cm−3, higher mobility increased by 187% to 150.2 cm2 V−1 s−1, and higher mobility–lifetime product increased by around 450% to 1.6 × 10−3 cm2 V−1, as compared with the ITC‐grown reference sample. The high performance of the CMTP‐based MAPbI3 X‐ray detector is comparable to that of a traditional high‐quality CdZnTe device, indicating the CMTP method as being a cost‐efficient strategy for high‐quality electronic‐grade semiconductor single crystals.

238 wileyonlinelibrary.com COMMUNICATION available highly purifi ed CNTs, with reported purity of up to 99.9% or even higher. [ 22 ] Another factor leads to the slow progress on the development of high-performance CNT IR detectors is that device structure and operation mode have not been optimized for solution-processed CNTs to achieve performance comparable with that of state-of-the-art commercial IR detectors. [ 23,24 ] In this letter, we show that high-performance photodiodes can be constructed using solution-processed CNTs via a dopingfree technique. In contrast to other photodetectors that use photocurrent as the signal, [ 8,[11][12][13][14][15][16][17][18][19][20] here we exploit using photovoltage as the signal. The major benefi t of using photovoltage is that the commonly occurring shot noise and 1/ f noise can be signifi cantly suppressed. In addition, signal can be multiplied via introducing virtual contacts, which leads to further improvement on signal-to-noise ratio. A prototype CNT IR detector is demonstrated, which works at room temperature and shows broadband response, high responsivity and detectivity that are comparable to that of state-of-the-art room temperature semiconductor IR detectors. It is also demonstrated that our CNT IR detectors have excellent stability, as a result of the dopingfabrication process used here, with time, under high power illumination and at rigorous temperature conditions. An array of 150 × 150 photodetectors on a single chip is fabricated, with tested yield of 100% and high device uniformity, showing the potential for large-scale fabrication capability and imager applications.In a typical photovoltaic device, a built-in fi eld is essential for the effi cient separation of photoinduced electron-hole pairs. For CNT-based diodes, ideal rectifi cation behavior has been realized by using split gates or asymmetric contacts on individual CNTs. [ 9,10,13 ] However, light absorption in these devices is usually very weak. It is thus advantageous to construct a photodiode using CNT fi lm with more CNTs in the device channel. However, solution-processed CNT-fi lm-based diodes showing excellent rectifi cation effect have not been realized. [ 23,24 ] Here, we show that such high-performance diode based on solutionprocessed CNT fi lm can be realized by using a doping-free technique in a barrier-free-bipolar diode (BFBD) device geometry as depicted in Figure 1 a. In this device geometry, Sc and Pd are asymmetrically contacted to a CNT fi lm made by a liquidphase deposition technique on an n + silicon/SiO 2 substrate (see Figure S1a,b, Supporting Information). Thus, p-region and n-region are automatically formed adjacent to the contacts by charge transfer from the contacts. This process involves no intentionally introduced dopants, no extra defects on CNTs,

The high-quality and low-cost of the graphene preparation method decide whether graphene is put into the applications finally. Enormous efforts have been devoted to understand and optimize the CVD process of graphene over various d-block transition metals (e.g. Cu, Ni and Pt). Here we report the growth of uniform high-quality single-layer, single-crystalline graphene flakes and their continuous films over p-block elements (e.g. Ga) liquid films using ambient-pressure chemical vapor deposition. The graphene shows high crystalline quality with electron mobility reaching levels as high as 7400 cm2 V−1s−1 under ambient conditions. Our employed growth strategy is ultra-low-loss. Only trace amounts of Ga are consumed in the production and transfer of the graphene and expensive film deposition or vacuum systems are not needed. We believe that our research will open up new territory in the field of graphene growth and thus promote its practical application.