Extraction of molecular negative-ion beams of CN from radio frequency plasma-sputter-type heavy negative ion source for negative-ion beam deposition

A high current CN negative-ion beam was obtained from a radio frequency plasma-sputter-type heavy negative ion source in a target-gas mode operation and CN negative-ion beam deposition was investigated. CN negative ions of 0.88 mA were safely obtained by using a carbon sputtering target and nitrogen gas instead of cyanogen for ionization. Even in this target-gas mode operation of the source with ${\mathrm{N}}_{\mathrm{2}}$ gas, the work function of the sputtering target surface was effectively decreased by introducing cesium vapor so that the production of CN negative ions was remarkably enhanced. In a CN negative-ion beam deposition on silicon substrate, the nitrogen concentration in deposited layers depended on ion energy and the maximum ratio (N/C) of 0.3 was obtained at an energy of 70 eV. From a Raman spectra with these results, it was found that CN-deposited films were a diamondlike carbon film including nitrogen atoms.