Coupled study by TEM/EELS and STM/STS of electronic properties of C- and CNx-nanotubes

Abstract

Carbon nanotubes are the focus of considerable research efforts due to their fascinating physical properties. They provide an excellent model system for the study of one dimensional materials and molecular electronics. The chirality of nanotubes can lead to very different electronic behaviours, either metallic or semiconducting. Their electronic spectrum consists of a series of Van Hove singularities defining a bandgap for semiconducting tubes and molecular orbitals at the corresponding energies. A promising way to tune the nanotubes electronic properties for future applications is to use doping by heteroatoms. Here we report on experimental investigation of the role of many-body interactions in nanotube bandgaps, the visualization in direct space of the molecular orbitals of nanotubes and the properties of nitrogen doped nanotubes using scanning tunneling microscopy and transmission electron microscopy as well as electron energy loss spectroscopy. RésuméEtude couplée par TEM/EELS et STM/STS des propriétés structurales et électroniques des nanotubes C et CN x Les nanotubes de carbone sont l'objet d'importants efforts de recherche en raison de leurs fascinantes propriétés physiques. Ils constituent un système modèle particulièrement intéressant pour l'étude fondamentale de matériaux à une dimension et pour l'électronique moléculaire. En fonction de leur chiralité, les nanotubes peuvent adopter un comportement électronique soit semiconducteur soit métallique. Leur spectre électronique est dominé par une série de singularités de Van Hove qui définit la bande interdite des tubes semiconducteurs et les orbitales moléculaires situées à ces énergies. Pour contrôler et moduler les propriétés électroniques des nanotubes, une voie prometteuse est d'utiliser le dopage par des hétéroatomes. Les travaux présentés ici portent sur l'étude expérimentale de l'influence des interactions à N corps sur la valeur de la bande interdite des tubes semiconducteurs, la visualisation dans l'espace direct des orbitales moléculaires des nanotubes et les propriétés des nanotubes dopés par l'azote en utilisant des mesures de microscopie tunnel, microscopie électronique à balayage et spectroscopie de perte d'énergie des électrons.

A Review on Characterizations and Biocompatibility of Functionalized Carbon Nanotubes in Drug Delivery Design

“…This is to enable the electrons to flow to/from a STM tip. The STM images of CNTs can be very much depending on the curvature radius of the tip, CNTs diameter, and the different chiralities exhibited by the CNTs itself [113]. Consequently, the attachment of functional groups to the surface of CNTs and the mechanical stability of the bonding can also be analyzed using STM [112].…”

Atomic Configuration of Nitrogen-Doped Single-Walled Carbon Nanotubes

“…Indeed, a clear and unambiguous proof of identification of individual dopants (N atoms in this case) in single-walled nanotubes has not yet been obtained, in contrast to the case of 2D materials (25), and the question remains whether electron microscopy is able to identify individual dopant atom configurations in such complex non-planar and beam-sensitive architectures. Here, we have carried out such experiments on single-walled, nitrogen-containing carbon nanotubes (CN x -SWNTs) synthesized via a laser vaporization technique (8,26). We clearly demonstrate the feasibility of dopant identification in a nanotube at the single-atom level.…”

“…Scanning tunneling microscopy (STM) and spectroscopy (STS) are local techniques for studying the structural and electronic features/properties of materials. Indeed, some studies have been reported on CN x -NT (7)(8)(9) and recently also on N-doped graphene (10,11). However, chemical characterization cannot be unambiguously performed from the STM/STS analysis.…”

“…However, chemical characterization cannot be unambiguously performed from the STM/STS analysis. Indeed, the interpretation of the results remains complicated, as different local structures may give rise to similar features (7)(8)(9)(10)(11). In this sense, high-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) combined with electron energy-loss spectroscopy (EELS) have provided very valuable and rich information at the atomic scale (12).…”

Long-range interactions between substitutional nitrogen dopants in graphene: Electronic properties calculations

“…7,8 Doping singlewall carbon nanotubes has also been considered. [9][10][11] Recent STM-STS experiments of N-doped graphene 5,8 have demonstrated the occurrence of chemical substitution. These experiments provide us with a detailed and local analysis with sub-atomic resolution of the electronic properties of the doped material.…”