Enhancement in electron field emission in ultrananocrystalline and microcrystalline diamond films upon 100 MeV silver ion irradiation

Enhanced electron field emission (EFE) behavior was observed in ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films upon irradiation with 100 MeV Ag9+-ions in a fluence of 5x1011 ions/cm2. Transmission electron microscopy indicated that while the overall crystallinity of these films remained essentially unaffected, the local microstructure of the materials was tremendously altered due to heavy ion irradiation, which implied that the melting and recrystallization process have occurred along the trajectory of the heavy ions. Such a process induced the formation of interconnected nanocluster networks, facilitating the electron conduction and enhancing the EFE properties for the materials. The enhancement in the EFE is more prominent for MCD films than that for UNCD films, reaching a low turn-on field of E0=3.2 V/μm and large EFE current density of Je=3.04 mA/cm2 for 5x1011 ions/cm2 heavy ion irradiated samples.