Ak. Gupta et P. Ayyub, Formation of nitrogen-substituted carbon cluster anions by gas-feed Cs-sputtering from different forms of carbon, EUR PHY J D, 17(2), 2001, pp. 221-229
We have investigated the mechanism of formation of C-n(-) and CnN- cluster
anions during Cs+-ion sputtering from surfaces of different crystallographi
c forms of carbon (polycrystalline graphite, amorphous C and C-60), in the
presence of high purity N-2 or NO2 gas. The normalised yields of sputter-ej
ected CnN- (n less than or equal to 10) cluster anions display an oscillato
ry 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 th
ree 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 ani
ons. The observed abundance patterns of C-n(-) and CnN- clusters also sugge
st that mono-nitrogen substitution of the carbon clusters does not allow th
e chain to ring transformation to occur up to n = 10.