B.2
Log Number: 60
Abstract Submitted to the NT-99-Logo NANOTUBE-99 Workshop:

In situ Raman Investigations of Single-Wall Carbon Nanotubes Under Pressure

E.D. Obraztsova1, H. Th. Lotz2, J.A. Schouten2 , M.E. Kooi2

1Natural Sciences Center of General Physics Institute, RAS, 38 Vavilov street, 117942, Moscow, Russia
2 Van der Waals-Zeeman Institute of the University of Amsterdam, Valckenierstraat 65-67, 1018 XE, The Netherlands
Contact e-mail: elobr@kapella.gpi.ru

The Raman spectra of single wall carbon nanotubes grown by laser ablation or arc discharge techniques under the pressures up to 10 GPa have been measured in situ in diamond anvil cell. The cell was filled with a buffer gas N2. The pressure value was controlled by measuring a position of the photoluminescence band of a tiny ruby chip admixed to SWNT. The breathing; mode was clearly seen at pressures below 1.5-2 GPa and disappeared at higher pressures. The TO mode shifted from the position 1592 cm-1 (at ambient pressure) toward high frequencies almost linearly with the pressure. The shift rate (4.9 cm-1/GPa) appeared to be very close to that of graphite. The splitting of TO mode (being a fingerprint; of SWNT) was observed at all steps of pressurizing. After unloading a complete spectrum recovering was observed if the pressure applied was less than 2.5 GPa. After the treatment at higher pressures the irreversible broadening and overlapping of the split components of TO mode remained. Such broadening increased with the pressure while a disorder degree of the material (characterized by so-called D; Raman peak at 1350 cm-1) didn't increase remarkably. A polymerization of nanotubes inside ropes followed by the graphite needles formation is discussed as a possible mechanism of SWNT transformation under the pressure.

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