Negative carbon (C−) and oxygen (O−) ions are expected to find wide applications for ion implantation processes. However, systematic experimental data required for their efficient generation and the elucidation of their underlying atomic processes are lacking. In this study, we systematically measured the angular and incident beam energy dependencies of the reflected carbon and oxygen ion properties from Mo, W, and low-work function material 12CaO⋅7Al2O3 electride targets, for low-energy (1 keV) carbon (C+) and oxygen (O+) ion injections. For all targets, both C+ and C− ions were reflected for the C+ ion injection, whereas only the reflected O− ions were observed for O+ ion injection. The energies of C+, C−, and O− ions reflected from the electride and Mo decreased significantly with increasing reflection angle. The effect of the lower work function was an increase in the intensity of the O− ions reflected at larger-incident and smaller-reflection angles by comparing the reflected ions from Mo and electride targets. On the other hand, the effect of the work function on the production of C− ions was small. When 1 keV-O+ ions were incident on W, the fraction of the reflected O− ions was 10%–30%, and the rest were neutral oxygen particles. Good agreement between the measured and calculated incident angular dependency of reflected O neutral particles was observed.
Yamaoka et al. (2026) studied this question.