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Surface Spectroscopy
of Nano and Subnano Structures

N. Afanasyeva*, R. Bruch, P. Kano, D. Schneider**

Department of Physics, University of Nevada,
Reno, Nevada 89503
**
Lawrence Livermore National Laboratory, P.O. Box 808,
Livermore, California 94550

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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