Low-dimensional nanomaterials, such as carbon nanotubes and few-layer graphene, are promising materials for realizing nanoelectronics in the next generation with new functions beyond those possible with conventional silicon and compound semiconductors. In our research group, structural control and functionalization of these nanomaterials are now being explored on the basis of surface and material science toward nano-integrated devices.
The electronic structure of carbon nanotubes (CNTs) is governed by “chirality”, or the spiral structure of C-C bonds and the CNT diameter. Aiming at chirality control, which is crucial for future applications of CNTs to nanoelectronics, we are doing the comprehensive research on the CNT growth process, such as exploration of new types of catalysts in the CVD growth and in situ spectroscopic observation of growing CNTs. We have found that gold-group elements (Au, Ag, Cu) and semiconductor (Si, Ge, SiC) particles, which had been believed to be inactive for CNT growth, can act as “seeds” to produce CNTs. In situ Raman observation clarifies the relation between the chemical states of catalyst nanoparticles and CNT structures. To draw out new functions from CNTs, defects formed on CNTs by low-energy irradiation of electrons or photons are intentionally manipulated to control the electrical properties of CNT devices. We have elucidated the energetics of the defect formation and recovery processes and have found a novel phenomenon, which is metal-semiconductor transition induced by defects formed in the channel of a CNT-FET. Graphene is another promising nanocarbon material for future nanoelectronics. We are using various techniques based on surface science to investigate synthesis and characterization of graphene. We have recently succeeded in evaluating the number of atomic layers in graphene formed on SiC substrates by low energy electron microscope (LEEM). A new microscope for probing optical and electrical properties of nanostructures with high spatial resolution is being developed with the intention of extending nanomaterials research to photonics applications.