Minoru Fukumori

Method for Controlling Electrical Properties of Single-Layer Graphene Nanoribbons via Adsorbed Planar Molecular Nanoparticles

A simple method for fabricating single-layer graphene nanoribbons (sGNRs) from double-walled carbon nanotubes (DWNTs) was developed. A sonication treatment was employed to unzip the DWNTs by inducing defects in them through annealing at 500 °C. The unzipped DWNTs yielded double-layered GNRs (dGNRs). Further sonication allowed each dGNR to be unpeeled into two sGNRs. Purification performed using a high-speed centrifuge ensured that more than 99% of the formed GNRs were sGNRs. The changes induced in the electrical properties of the obtained sGNR by the absorption of nanoparticles of planar molecule, naphthalenediimide (NDI), were investigated. The shape of the I-V curve of the sGNRs varied with the number of NDI nanoparticles adsorbed. This was suggestive of the existence of a band gap at the narrow-necked part near the NDI-adsorbing area of the sGNRs.

Tuning the electrical property of a single layer graphene nanoribbon by adsorption of planar molecular nanoparticles

In this study, a simple and fast approach of band gap formation in a single layer graphene nanoribbon (sGNR) is demonstrated by using hexaazatriphenylenehexacarbonitrile (HAT-CN6) as an adsorbate molecule. sGNRs were successfully synthesized through the unzipping of double-walled carbon nanotubes followed by casting HAT-CN6 in acetone solution to alter the electronic properties of the sGNRs. Then, the electrical property of a sGNR was measured using a field effect transistor structure and also by point-contact current imaging atomic force microscopy. The results demonstrate the formation of electron trapping sites with the nanoparticles and the neck structure of the sGNR near the adsorbed region of the molecule. Therefore, the charge carriers on the sGNR can only pass through the neck region, which works similarly to a narrow sGNR. Such a narrow sGNR has a lateral confinement of charge carriers around the neck region; hence, the device becomes semiconducting. The fabricated semiconducting sGNR could be widely used in electronic devices.

Synthesis of very narrow multilayer graphene nanoribbon with turbostratic stacking

A multilayer graphene nanoribbon (GNR) less than 20 nm wide was synthesized by overlayer growth of graphene on a GNR template. First, very narrow template GNRs with widths of approximately 10 nm were prepared by unzipping from double-walled carbon nanotubes. Additional 4–5 layers of graphene were then formed on the pristine GNR template by chemical vapor deposition. Raman spectroscopy revealed that the synthesized multilayer GNR had turbostratic stacking without any structural correlation between the graphene layers. A large on/off ratio and a high on-current were observed in field effect transistors fabricated using the synthesized multilayer GNR channel.

Diameter dependence of longitudinal unzipping of single-walled carbon nanotube to obtain graphene nanoribbon

Graphene nanoribbons (GNRs) were successfully synthesized by the longitudinal unzipping of a single-walled carbon nanotube (SWNT). In this process, a short-duration sonication was performed to unzip the SWNT. The obtained results clearly show that the synthesized GNR is semiconducting. Furthermore, it is also confirmed by Raman spectroscopy that the time variation of the samples during the unzipping process has two types of reaction, namely, fast and slow. Furthermore, the obtained results confirm that the narrower SWNT should be unzipped quickly, whereas the wider SWNT should be unzipped slowly.

Progress on nanoparticle-based carbon nanotube complex: fabrication and potential application

Abstract Carbon nanotubes (CNTs) are considered as one of the most intensively explored nanostructured materials and have been widely used as a platform material for metal and semiconductor nanoparticles (NPs) due to their large and chemically active surface area. Several approaches have been described in the literature to immobilize NPs on the surface of CNTs. This report reviews the recent developments in this area by exploring the various techniques where nanotubes can be functionalized with NPs to improve the optical, mechanical, thermal, medical, electrical, and magnetic applications of CNTs.

Functionality emergence of single molecule electronics

In these decades organic functional materials have been utilized in daily electronic products like organic light emitting diodes or liquid crystals in cellar phones or televisions. At the present stage organic materials are used as mass materials and the most characteristic properties of them arise from cooperative effects of each molecule. However, if each single molecule has their own specific properties and cooperate in a rational way with each other, they should emerge more sophisticated properties. In this regard, we have been studying electronic or magnetic properties of single or small number of molecules, synthetic route for molecular integrated circuits by a successive coupling of the molecular parts, by self-assembling on surface, and combination with carbon nano-materials. In order to emerge new properties, each molecule units should show non-linear and non-symmetric responses. We have been studying design, synthesis, and measurements of organic molecules which can exhibit such responses in single molecules.