• caratterizzazione elettrica di nanotubi
• dispersione di nanotubi
• interconnects
• isolamento di nanotubi
• nanoscienze
• nanotecnologie
• nanotubi di carbonio

Carbon nanotubes (CNTs) are currently the focus of intense interdisciplinary
research activity, because they display remarkable physical and chemical properties
and because of their prospects for novel technologies. The experimental
motivation of this thesis are recent results on individual single-walled carbon nanotubes
(SWCNTs) and multi-walled carbon nanotubes (MWCNTs), due to
the necessity of their physical characterization before any potential application,
which spans a wide range, from mechanical to electrical and thermal ones.
We introduce the basic concepts and theoretical expectations for the electrical
transport properties of CNTs. In particular, we review the electronic properties
of graphene, SWCNTs and MWCNTs first, and then the electrical transport
properties of nanotubes in zero magnetic field at room temperature. Finally, we
present our local and non-local electrical transport measurements on an individual
MWCNT performed in zero magnetic field at room temperature, since our
goal is to characterize individual pristine MWCNTs. Experimentally MWCNTs
are found to be either conducting or non-conducting and currently there are no
production or separation methods that can yield bulk quantities (milligram or
larger) of metallic nanotubes. As a result, we aim at determining whether our
MWCNT is conducting or non-conducting, that is, metallic or insulator.
For the purposes of physical characterization, we have previously aimed at
developing an original and creative method for separation first and then isolation of a pristine MWCNT, because pristine nanotubes are packed together in bundles
due to strong van der Waals attraction. Few solvents disperse pristine CNTs,
but one point of concern with them is that they may influence substantially the
physical properties of the nanomaterial and induce unwanted chemical reactions
such as protonation and oxidation. So, we have striven to study a non-destructive
process that avoids damages to tube walls or tips and preserves the
integrity of nanotubes, even during atomic force microscope (AFM) and focused
ion beam (FIB) imaging of the collected samples. Moreover, we have striven to
establish Ohmic contacts to these individual, clean and undamaged MWCNTs
by means of FIB deposition onto metal electrodes of a silicon device, since, when
the contact is not good, non-linear current-voltage (I-V) curves are obtained,
even though the contacted nanotube is metallic. These are key issues from
a physical standpoint, as we then focus our efforts on investigating the intrinsic
properties of MWCNTs.