Reproducibility of O- Negative Ion Emission from C12A7 Crystal Surface

Reproducibility, stability and oxygen-pressure dependence of O- negative ion emission from a synthesized crystal 12CaO·7Al2O3 (C12A7) surface have been investigated. We found the continuous O- implantation into the C12A7 crystal can be simply realized by supplying electron and oxygen on the Au-deposited C12A7 surface via electrocatalytic reactions. The O- emission from the consumed C12A7 surface was recovered after the implantation operation (O2: 0.13 Pa; 770°C) for 30 minutes. In contrast, the implantation influence on electron emission is negligible. The O- emission intensity is nearly constant in the O2 pressure lower than 1×10-3 Pa. The O- implantation mechanism will be addressed.