SPUTTER EMISSION OF NEGATIVELY CHARGED CARBON CLUSTERS

The negative cluster ion mass distribution under cesium impact of grap hite and amorphous carbon samples was studied using a cesium sputter n egative ion source. In the case of graphite sputtering, the regular od d-even oscillations with the even clusters being higher in intensity t han the odd ones for C-n(-) upto n=9 and a reversal in this trend for n>13 as observed by several others' was confirmed. On the other hand, in the case of amorphous carbon sputtering, the intensity distribution pattern was seen to be similar to that of graphite upto n=9, but the trend of even clusters having higher intensity continued upto n=17, be yond which the pattern was similar to that of graphite. In the case of amorphous carbon sputtering, the intensity drop from C-2 to C-18 can be represented by a power law with a single exponent, whereas in the c ase of graphite sputtering, two different exponents are required to ex plain the slower fall from C-2 to C-8 followed by a steeper drop from C-9 to C-18 Further, the intensity distribution of the CsCn- clusters was also found to be different in the two cases.