Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Every few years, a new material with unique properties emerges and fascinates the scientific community, typical recent examples being high-temperature superconductors and carbon nanotubes. Graphene is the latest sensation with unusual properties, such as half-integer quantum Hall effect and ballistic electron transport. This two-dimensional material which is the parent of all graphitic carbon forms is strictly expected to comprise a single layer, but there is considerable interest in investigating two-layer and few-layer graphenes as well. Synthesis and characterization of graphenes pose challenges, but there has been considerable progress in the last year or so. Herein, we present the status of graphene research which includes aspects related to synthesis, characterization, structure, and properties.

Graphene: The New Two-Dimensional Nanomaterial

Graphene based materials: Past, present and future

We report values of pseudodielectric functions $〈\ensuremath{\epsilon}〉=〈{\ensuremath{\epsilon}}_{1}〉+i〈{\ensuremath{\epsilon}}_{2}〉$ measured by spectroscopic ellipsometry and refractive indices $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{n}=n+ik$, reflectivities $R$, and absorption coefficients $\ensuremath{\alpha}$ calculated from these data. Rather than correct ellipsometric results for the presence of overlayers, we have removed these layers as far as possible using the real-time capability of the spectroscopic ellipsometer to assess surface quality during cleaning. Our results are compared with previous data. In general, there is good agreement among optical parameters measured on smooth, clean, and undamaged samples maintained in an inert atmosphere regardless of the technique used to obtain the data. Differences among our data and previous results can generally be understood in terms of inadequate sample preparation, although results obtained by Kramers-Kronig analysis of reflectance measurements often show effects due to improper extrapolations. The present results illustrate the importance of proper sample preparation and of the capability of separately determining both ${\ensuremath{\epsilon}}_{1}$ and ${\ensuremath{\epsilon}}_{2}$ in optical measurements.

Dielectric functions and optical parameters of Si, Ge, GaP, GaAs, GaSb, InP, InAs, and InSb from 1.5 to 6.0 eV

Carbon nanotubes (CNTs) hold the promise of delivering exceptional mechanical properties and multi-functional characteristics. Ever-increasing interest in applying CNTs in many different fields has led to continued efforts to develop dispersion and functionalization techniques. To employ CNTs as effective reinforcement in polymer nanocomposites, proper dispersion and appropriate interfacial adhesion between the CNTs and polymer matrix have to be guaranteed. This paper reviews the current understanding of CNTs and CNT/polymer nanocomposites with two particular topics: (i) the principles and techniques for CNT dispersion and functionalization and (ii) the effects of CNT dispersion and functionalization on the properties of CNT/polymer nanocomposites. The fabrication techniques and potential applications of CNT/polymer nanocomposites are also highlighted.

Dispersion and functionalization of carbon nanotubes for polymer-based nanocomposites: a review

Planer nano-graphenes from camphor by CVD

Doping of different elements in intrinsic graphene is of great importance to adjust the electrical and chemical properties for realization of different electronic devices. Here, we demonstrate a simple and controllable synthesis process of iodine-doped graphene film using camphor (C10H16O), a solid botanical derivative. In situ doping of iodine in a graphene film has many difficulties in a conventional chemical vapor deposition process using a gas source. In this technique, iodine was mixed with the carbon precursor and simultaneously evaporated to pyrolysis on a metal catalytic substrate. Raman and X-ray photoelectron spectroscopic studies confirm the presence of elemental iodine in the form of triiodide and pentaiodide. Simultaneously, evaporated iodine atoms remains within the few-layers graphene structure and interact with carbon atoms through a charge transfer process. This shows a straightforward technique for iodine doping in graphene and a similar approach can be adopted to deposit iodine-doped graphene on other metal substrates.

Iodine doping in solid precursor-based CVD growth graphene film

Here, we report the synthesis of a graphene film on Cu foil by microwave assisted surface wave plasma chemical vapor deposition (MW-SWP-CVD) at a low pressure and temperature using a hydrocarbon gas. Raman spectroscopy and transmission electron microscopy (TEM) studies clearly show deposited carbon films that consist of few layer graphene sheets. Deposition of graphene films with a few layers structure was achieved at a temperature as low as 240 °C. In the nucleation and growth process, carbon radicals are formed with hydrogen termination in the surface wave plasma, which absorb continuously on the Cu surface to form sp2 carbon and eventually a graphene structure. The transparency and conductivity characteristics of the transferred graphene films show suitability for flexible electronics applications.

Low temperature growth of graphene film by microwave assisted surface wave plasma CVD for transparent electrode application

Carbon nanotubes by spray pyrolysis of turpentine oil at different temperatures and their studies

AlGaAs/GaAs double heterostructure laser diodes have been fabricated on Si substrates using GaP/(GaP/GaAsP) superlattice/(GaAsP/GaAs) superlattice intermediate layers grown by metalorganic chemical vapor deposition. A threshold current density at 16.5 °C and a characteristic temperature T0 of 4.9 kA/cm2 and 179 K respectively have been obtained for the diode on Si substrate.

https://nitech.repo.nii.ac.jp/?action=repository_action_common_download&item_id=3849&item_no=1&attribute_id=39&file_no=1

Masayoshi Umeno

Papers

Planer nano-graphenes from camphor by CVD

Iodine doping in solid precursor-based CVD growth graphene film

Low temperature growth of graphene film by microwave assisted surface wave plasma CVD for transparent electrode application

Carbon nanotubes by spray pyrolysis of turpentine oil at different temperatures and their studies

Room-temperature laser operation of AlGaAs/GaAs double heterostructures fabricated on Si substrates by metalorganic chemical vapor deposition