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Honeycomb Carbon: A Review of Graphene

Electrolytes and interphases in Li-ion batteries and beyond.

To realize graphene-based electronics, various types of graphene are required; thus, modulation of its electrical properties is of great importance. Theoretic studies show that intentional doping is a promising route for this goal, and the doped graphene might promise fascinating properties and widespread applications. However, there is no experimental example and electrical testing of the substitutionally doped graphene up to date. Here, we synthesize the N-doped graphene by a chemical vapor deposition (CVD) method. We find that most of them are few-layer graphene, although single-layer graphene can be occasionally detected. As doping accompanies with the recombination of carbon atoms into graphene in the CVD process, N atoms can be substitutionally doped into the graphene lattice, which is hard to realize by other synthetic methods. Electrical measurements show that the N-doped graphene exhibits an n-type behavior, indicating substitutional doping can effectively modulate the electrical properties of graphene. Our finding provides a new experimental instance of graphene and would promote the research and applications of graphene.

Synthesis of N-Doped Graphene by Chemical Vapor Deposition and Its Electrical Properties

Graphitic carbon nitride, g-C3N4, can be made by polymerization of cyanamide, dicyandiamide or melamine. Depending on reaction conditions, different materials with different degrees of condensation, properties and reactivities are obtained. The firstly formed polymeric C3N4 structure, melon, with pendant amino groups, is a highly ordered polymer. Further reaction leads to more condensed and less defective C3N4 species, based on tri-s-triazine (C6N7) units as elementary building blocks. High resolution transmission electron microscopy proves the extended two-dimensional character of the condensation motif. Due to the polymerization-type synthesis from a liquid precursor, a variety of material nanostructures such as nanoparticles or mesoporous powders can be accessed. Those nanostructures also allow fine tuning of properties, the ability for intercalation, as well as the possibility to give surface-rich materials for heterogeneous reactions. Due to the special semiconductor properties of carbon nitrides, they show unexpected catalytic activity for a variety of reactions, such as for the activation of benzene, trimerization reactions, and also the activation of carbon dioxide. Model calculations are presented to explain this unusual case of heterogeneous, metal-free catalysis. Carbon nitride can also act as a heterogeneous reactant, and a new family of metal nitride nanostructures can be accessed from the corresponding oxides.

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Graphitic carbon nitride materials: variation of structure and morphology and their use as metal-free catalysts

Polymeric graphitic carbon nitride materials (for simplicity: g-C(3)N(4)) have attracted much attention in recent years because of their similarity to graphene. They are composed of C, N, and some minor H content only. In contrast to graphenes, g-C(3)N(4) is a medium-bandgap semiconductor and in that role an effective photocatalyst and chemical catalyst for a broad variety of reactions. In this Review, we describe the "polymer chemistry" of this structure, how band positions and bandgap can be varied by doping and copolymerization, and how the organic solid can be textured to make it an effective heterogenous catalyst. g-C(3)N(4) and its modifications have a high thermal and chemical stability and can catalyze a number of "dream reactions", such as photochemical splitting of water, mild and selective oxidation reactions, and--as a coactive catalytic support--superactive hydrogenation reactions. As carbon nitride is metal-free as such, it also tolerates functional groups and is therefore suited for multipurpose applications in biomass conversion and sustainable chemistry.

Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst: From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry

An extended solid bulk composition carbon nitride (C 3 N 4 ) having an atomic ratio of carbon to nitrogen in the range of 3:4 to 3.2:4 as a bulk solid, produced by thermal decomposition and chemical vapor deposition of precursors having formula (I): C.sub.3 N.sub.3 XX'N(MR.sub.3)(M'R'.sub.3) (I) wherein C3N3 is a cyclic 1,3,5-triazine group, X is a halogen selected from the group consisting of fluorine, chlorine, bromine, and iodine, X' is a halogen selected from the group consisting of fluorine, chlorine, bromine, and iodine, M is a group IV metal, M' is a group IV metal, R is an alkyl substituent, and R' is an alkyl substituent, producing a decomposition gas decomposition gas having formula II: XMR.sub.3 (II)

Carbon nitride and its synthesis

Detectors based on such Ge(Sn) alloys of the formula Ge 1-x Sn x (e.g., 0 < x < 0.01) have increased responsivity while keeping alloy scattering to a minimum. Such small amounts of Sn are also useful for improving the performance of the recently demonstrated Ge-on-Si laser structures, since the addition of Sn monotonically reduces the separation between the direct and indirect minima in the conduction band of Ge. Thus, provided herein are Ge(Sn) alloys of the formula Ge 1x Sn x , wherein x is less than 0.01, wherein the alloy is optionally n-doped or p-doped; and assemblies and photodiodes comprising the same, and methods for their formation.

Dilute sn-doped ge alloys

Precursors for group IV epitaxy for micro/opto-electronic applications

New unimolecular carbon-nitride precursors such as C{sub 3}N{sub 3}F{sub 2}N(SiMe{sub 3}){sub 2} and C{sub 3}N{sub 3}Cl{sub 2}N(SiMe{sub 3}){sub s} were synthesized and used to deposit thin films of composition C{sub 3}N{sub 4}-C{sub 3.2}N{sub 4}, the highest nitrogen content observed in C-N solids. The films were formed by the thermal decomposition of the precursors via elimination of SiMe{sub 3}F and SiMe{sub 3}Cl at 400-500 {degrees}C. Film thicknesses between 1200 and 4000 {Angstrom} were deposited on (100) Si, graphite, beryllium, and SiO{sub 2}, and were extensively characterized for composition and chemical purity using RBS, energy-dispersive X-ray analysis, and SIMS. The material was amorphous as indicated by X-ray diffraction. IR, EELS, and {sub 13}C NMR reveal substantial sp{sup 2} hybridization in both the carbon and the nitrogen. This material should be an excellent precursor for the high-pressure synthesis of C{sub 3}N{sub 4}, the highly sought structural and compositional analog of Si{sub 3}N{sub 4}. 12 refs., 4 figs.

Novel Synthetic Routes to Carbon‐Nitrogen Thin Films.

Electrical properties of p-Ge1−ySny (y = 0.06%) grown on n-Si substrate were investigated through temperature-dependent Hall-effect measurements. It was found that there exists a degenerate parallel conducting layer in Ge1−ySny/Si and a second, deeper acceptor in addition to a shallow acceptor. This parallel conducting layer dominates the electrical properties of the Ge1−ySny layer below 50 K and also significantly affects those properties at higher temperatures. Additionally, a conductivity type conversion from p to n was observed around 370 K for this sample. A two-layer conducting model was used to extract the carrier concentration and mobility of the Ge1−ySny layer alone.

John Kouvetakis

Papers

Carbon nitride and its synthesis

Dilute sn-doped ge alloys

Precursors for group IV epitaxy for micro/opto-electronic applications

Novel Synthetic Routes to Carbon‐Nitrogen Thin Films.

Degenerate parallel conducting layer and conductivity type conversion observed from p-Ge1−ySny (y = 0.06%) grown on n-Si substrate