Nitrogen and phosphorus doped single-wall carbon nanotubes

The main objective of the NIPHOTUBES project is to develop a significantly enhanced understanding of the atomic bonding of nitrogen and phosphorus dopants in single-walled carbon nanotubes. While nanotubes possess several exceptional and unique properties, their electronic nature depends on their precise structure, which still cannot be controlled despite immense research efforts. This presents a problem for applications, since nanotubes of a specific type are typically required. Another way to control their properties is by substitutional doping with other chemical elements. However, such research has been hampered by the limited availability of doped materials and the difficulty of conclusively identifying the dopant sites. The work in this project is distributed into four Work Packages (WP): Characterization, Modeling, Transport, and Dissemination. The Characterization WP utilizes a comprehensive array of complementary spectroscopic and microscopic methods, for which the chosen host site is ideally suited. The experimental activities are supported by advanced computational work in the Modeling WP, giving the research multidisciplinary appeal. Apart from his expertise on the topic, major part of the materials synthesis will be accomplished prior to the beginning of the project at the present research site of the applicant. He will have full access to the required synthesis systems and thus avoid the need to build additional reactors at the research site. Pre-existing international collaborations of the applicant are also key to achieving the goals of the Transport WP, and will contribute significantly to the Characterization and Modeling WPs. The rigorous multimodal characterization of the materials will allow elucidating the influence of doping on the nanotubes` properties, particularly on quantum transport. The results will set higher standards for the study of all doped nanocarbon materials, leading to enhanced control over their production. The significance for metrology will be considerable, helping set a more robust scientific foundation for substitutional doping and paving the way to its wider adoption. Phosphorus doping has rich untapped potential and potential for scientific breakthroughs. If theoretical predictions of exclusively n-type doping can be realized, P-doped SWCNTs would enable the production of natively n-type nanotube transistors.

Significant progress in understanding the bonding of phosphorus (P) atoms in single-walled carbon nanotubes was achieved during the NiPhoTubes project. Although nanotubes possess several exceptional and unique properties, their electronic nature depends on their precise structure. This presents a problem for applications, since nanotubes of a specific type are typically required. Another way to control their properties is by substitutional doping, that is, replacing some carbon atoms with atoms of another element. However, such research has been hampered by the limited availability of doped materials and the difficulty of conclusively identifying the dopant sites. As a highlight of the project, we made a pioneering study on measuring the bonding of phosphorus in carefully purified samples confirming its feasibility as a dopant, and were further able to directly image a single P dopant in graphene. Finally, although not part of the original project goals, our finding that an electron beam could be used to move dopant atoms controllably in the graphene lattice may prove to be a major discovery, contributing to pushing the limits of what is technologically possible in science.