On the mechanism of enhancement on electron field emission properties for ultrananocrystalline diamond films due to ion implantation

The effects of N and C ion implantations on modifying the structural and field emission properties of ultrananocrystalline diamond (UNCD) films were investigated. Low dose ion implantations possibly introduced point defects, which were easily removed by the annealing process. The nature of the doping species, N or C, was immaterial. In contrast, high dose N ion implantation induced the formation of the amorphous phase, which was converted into the graphitic phase after annealing, and improved the field emission properties (J(e) was increased to similar to 6.3 mA cm(-2) at 20 V mu m(-1)). However, the high dose C ion implantation induced the graphitic phase directly, which degraded the field emission characteristics, i.e. J(e) was lowered to similar to 0.6 mA cm(-2) at 20 V mu m(-1). The variations in the electron field emission properties for ion-implanted UNCD films are accounted for by the nature of the induced defects and the electron transfer doping mechanism.