•Cu nanoparticles and were fabricated in the in UNCD film by ion implantation.•Mesh-like surface structures appear in UNCD film after 500 °C rapid annealing.•Enhanced carrier mobility of 346.5 cm2 V−1 S−1was observed after rapid annealing.•Cu NPs provoked the formation of high-electron-mobility nanographite•The conduction mechanism for the improved conductivity was discussed.The effects of 100 keV Cu ion implantation and subsequent annealing (i.e. common annealing or rapid annealing) at 500 °C on modifying the surface morphology and the electron field emission (EFE) properties of ultrananocrystalline diamond (UNCD) films were investigated. A Common annealing provides moderate enhancement in both electrical and EFE properties. Besides, the rapid annealing results in a low surface resistivity of 10.3 Ω/sq with a high mobility of 346.5 cm2 V−1 S−1for the UNCD film. The corresponding EFE behavior can be turned on at E0 = 5.3 V/μm, attaining a current density of 426.7 μA/cm2 at an applied field of 8.1 V/μm. The Mesh-like surface structures with the plate-like particulates, approximately 20–30 nm in size, distributed on the sample surface, which implies that the melting and recrystallization process have occurred due to the rapid annealing. Raman and X-ray photoelectron microscopy results demonstrated that the formation of Cu nanoparticles in UNCD films could catalytically provoke the formation of abundant nanographitic phase during rapid annealing process, forming the conduction channels for electron transport. Finally, the conducting and EFE properties of the UNCD films were remarkably improved.

•Ag nanoparticles were fabricated in the free-standing diamond film by ion implantation.•Ag SPR peak at about 375 nm appears after 500 °C annealing.•Ag-embedded FSD films exhibited an enhanced carrier mobility after 500 °C annealing.•Ag nanoparticles act as conductive paths permitting charges to pass through them.•The Ag-embedded free-standing diamond films still shows high sp3-bonds.An optical-grade, free-standing diamond (FSD) film is prepared by home-made microwave plasma chemical vapor deposition reactor at a condition of input power 8 kW and gas pressure18 kPa. Then, it is implanted with 80 keV Ag ions up to a fluence of 5.0 × 1016 ions/cm2. After implantation, a subsequent annealing in Ar ambient at 500 °C is carried out to fabricate Ag nanoparticles (NPs). Grazing incidence x-ray diffraction results clearly showed that Ag NPs with a (111) orientation are effectively formed after 500 °C annealing. Results from field emission scanning electron microscope and atomic force microscope observations indicated that Ag NPs could aggregate and grow on the surface of the diamond film during the annealing process. The Hall effects results showed that Ag-implanted FSD film exhibited an enhanced carrier mobility of 34.7 cm2 V−1 S−1 after 500 °C annealing. Moreover, Raman spectroscopy results show that the damages of the Ag-implanted FSD film are essentially a little and the crystallinity is almost recovered by annealing, it is implied that the enhancement in carrier mobility could be attributed to the conductive paths provided by Ag NPs.

•Ag nanoparticles were introduced into the free-standing diamond film by ion implantation.•electrical conductivity and electron field emission properties was enhanced.•Ag nanoparticles act as conductive paths permitting charges to pass through them.•a relatively narrow barrier between Ag NPs and diamond grains was formed.•The origin of improving the EFE was discussed based on F-N equation.Ag nanoparticles (NPs) were introduced into free-standing diamond (FSD) film by ion implantation to improve its electrical conductivity and electron field emission (EFE) property. Ag-implanted FSD film exhibits improved conductivity with the carrier mobility of 16.2 cm2 V−1s−1, owing to the conductive paths provided by Ag NPs. The EFE behavior of Ag -implanted FSD film can be turned on at E0=18 V/μm, attaining a current density of 89.6 μA/cm2 at an applied field of 30 V/μm. The origin of improving the EFE was discussed based on F-N equation. The present study shows the interest of using embedded conductive NPs to improve the EFE of diamond.