Formation of nitrogen-substituted carbon cluster anions by gas-feed Cs-sputtering from different forms of carbon
Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
2 Department of Condensed Matter Physics & Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
Revised: 17 August 2001
Published online: 15 November 2001
We have investigated the mechanism of formation of C and CnN- cluster anions during Cs+-ion sputtering from surfaces of different crystallographic forms of carbon (polycrystalline graphite, amorphous C and C60), in the presence of high purity N2 or NO2 gas. The normalised yields of sputter-ejected CnN- () cluster anions display an oscillatory dependence on n: the odd n clusters being more abundant than the even n ones. Significantly, CnN- clusters produced from the three different forms of C, show similar oscillatory variations with n. Moreover, the CnN- yields follow a single power law decline as a function of cluster size for all three surfaces sputtered, and over a wide range of operating conditions. This strongly indicates that the intrinsic structure of the ion-induced surface does not play a significant role in the formation of sputtered cluster anions. The observed abundance patterns of C and CnN- clusters also suggest that mono-nitrogen substitution of the carbon clusters does not allow the chain to ring transformation to occur up to n = 10.
PACS: 36.40.Qv – Stability and fragmentation of clusters / 36.40.Wa – Charged clusters / 61.46.+w – Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001