Search results

Sort By:

Limit search:

Positron Annihilation in Carbon Nanotubes Studied by Coincidence Doppler Broadening Spectroscopy

100%

Murakami H., Sato K., Kanazawa I., Sano M.

Acta Physica Polonica A

2008

vol. 113

issue 5

1479-1484

In order to assign the sites of positron annihilation, coincidence Doppler broadening spectra were measured for a highly oriented pyrolytic graphite crystal, graphite powder, multi-walled carbon nanotubes (MNTs) and cup-stacked carbon nanotubes (CNTs). The spectrum for graphite powder normalized to that for highly oriented pyrolytic graphite (HOPG) is almost flat in the momentum region from 7×10^{-3} to 13×10^{-3} m_{e}c, having a ratio close to unity. The flat spectrum demonstrates that positrons injected into graphite powder annihilate in the interlayer spaces of piled graphite sheets, in the same manner as positrons in highly oriented pyrolytic graphite annihilate in the bulk. The coincidence Doppler broadening spectra for MNTs and CNTs are quite different from that for highly oriented pyrolytic graphite, which indicates that positrons injected into MNTs and CYTs annihilate not in the bulk, but on surface. The positron lifetime spectrum for multi-walled carbon nanotubes is analyzed in terms of a single component due to surface-trapped positrons, while that for CNTs is decomposed into three components attributable to para-positronium surface-trapped positrons and ortho-positronium. The difference between the coincidence Doppler broadening spectrum for CNTs and that for MNTs is explained in terms of positron annihilation on zigzag surfaces of CNTs which are composed of both graphite-sheet and graphite-edge planes.

Refine search results

1 Acta Physica Polonica A

1 2008

1 Kanazawa I.

1 Murakami H.

1 Sano M.

1 Sato K.

Search results

Positron Annihilation in Carbon Nanotubes Studied by Coincidence Doppler Broadening Spectroscopy