Kazunori Anazawa

High-purity carbon nanotubes synthesis method by an arc discharging in magnetic field

We developed a synthesis method of multiwalled carbon nanotubes (MWNTs), in which an arc discharging was controlled by a magnetic field. Using this method, we can obtain high-purity MWNTs (purity >95%) without purification which disorders walls of MWNTs. The current–voltage measurements show that the carriers would transport ballistically through our defect-free MWNTs with the maximum current density of ∼1011 A/m2. Therefore, our method provides defect-free/high-purity MWNTs as nanosized electric wires for device fabrication.

Studies on electronic structures of semiconductors by atomic force microscopy

We propose a new method of electron spectroscopy. Using an atomic force microscope, we have measured attractive forces between a sample and a metal coated tip with varying applied voltage in dry nitrogen atmosphere. We have then plotted the values as a function of the voltage to obtain a force spectrum. The spectra of Si, ZnSe, and diamond show band gap structures which can be explained by a charge–transfer model. The spectrum of C60 single crystal shows an energy gap of ∼2.0 eV and a highest occupied–lowest unoccupied molecular orbital (HOMO–LUMO) separation of 3.8 eV. These results are in good agreement with the energy gap and the HOMO–LUMO separation obtained by electron spectroscopy, respectively. The spectrum of C60 also reveals the features of density of state, which are in fairly good agreement with those obtained by electron spectroscopy. Application of this method to anthracene and p-terphenyl single crystals allowed us to discuss the natures of valence and conduction bands.