Surface Spectroscopy
of Nano and Subnano Structures
N. Afanasyeva*, R. Bruch, P. Kano, D.
Schneider**
This is an abstract
for a poster to be presented at the
Fifth
Foresight Conference on Molecular Nanotechnology.
The full paper is available here.
In light of recent progress in the fabrication and diagnostics
of nanostructures and surfaces, more advanced spectroscopic
methods are necessary in order to elucidate the detailed
structure, nature, and creation of such microsystems. We
present here some selected techniques which appear especially
promising, namely vibrational spectroscopy methods[1] and highly
charged ion surface interaction using an Electron
Beam Ion Trap (EBIT) facility[2]. Specifically we focus
here on the microspectroscopy of nanostructures originating from
carbon-graphite structures commonly called nanotubes.
Different nanotubes (powder, thin films and tubes from graphite
matrix) with diameter of the order of 10 to 20 angstrom and
length of 10 angstrom have been studied where the nanotubes are
oriented on different surfaces. We have observed middle
infrared (MIR) spectra of these samples in the region from 500 to
1200 cm-1. Characteristic bands have been
observed at 1085-1100, 930-790, 680 and 513 cm-1.
The main differences between these spectra are related to the
size of the nanotube systems. Additional information has
been obtained by measuring the series of overtones and
combination modes in the near infrared (NIR) (7000-4000 cm-1)
region. Furthermore, microRaman spectra of the carbon-base
of materials and their new forms have been recorded. The
materials were prepared under high pressure and temperatures
leading to several new superhard structures. From the
spectra, the level of disorder in such polymer forms of carbon
and graphite was determined.
Another promising method of nano and subnano structure
fabrication on surfaces involves heavy highly charged ion-surface
interaction. In this process a large amount of potential
energy is deposited by single ions at the surface leading to the
localized surface defects of subnano size. Here we present
new results on highly charged Biq+ (q=50 to 71) ions
interacting with gold surfaces. A detailed experimental and
theoretical comparison is provided for the X-ray spectra from the
gold surface. These data have been measured at the Lawrence
Livermore National Laboratory (LLNL) Electron Beam Ion Trap
(EBIT) highly charged ion facility. The comparison of our
computer simulations with experimental X-ray spectra provides
evidence for the formation of sub-surface hollow atoms. In
particular, a striking orbital (n) and angular momentum (l)
dependence for hollow atoms formation has been found shedding
more light on the dynamics of complex ion-surface and ion-solid
interaction processes. Finally, new developments in imaging
on an angstrom scale using heavy highly charged ions are
discussed.
References
[1] W. Clark, D. Schneider, D. Dewitt, J. W.
McDonald, R. Bruch, U. I Safronova, I. Yu Tolstikhina, R. Schuch,
Xe L and M X-ray emission following Xe44-48+ ion
impact on Cu surfaces, Phys. Rev. A., 47, 3983 (1993).
[2] EBIT Electron Beam Ion Trap, Annual Report
1995, Lawrence Livermore National Laboratory
*Corresponding Address:
Dr. Natalia Afanasyeva, Department of Physics, University of
Nevada, Reno, Nevada 89557-0058, ph: 702-784-6792, fax:
702-784-1398
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