Catalytically induced nanographitic phase by a platinum-ion implantation/annealing process to improve the field electron emission properties of ultrananocrystalline diamond films

Abstract

We report a Pt-ion implantation/annealing process for enhancing the electrical conductivity and the field electron emission (FEE) properties of ultrananocrystalline diamond (UNCD) films. Platinum ion implantation was performed on UNCD films at room temperature with the implantation energy of 500 keV and the ion dosages were varied from 1 × 10¹⁵ to 1 × 10¹⁷ ions per cm² at an ion flux of 1.035 × 10¹² ions per cm² per s. The UNCD films, which were Pt-ion implanted with 1 × 10¹⁷ ions per cm² and annealed at 600 °C possess the high electrical conductivity of 94.0 ohm⁻¹ cm⁻¹ and low turn-on field of 4.17 V μm⁻¹ with the high FEE current density of 5.08 mA cm⁻² (at 7.2 V μm⁻¹). Current imaging tunneling spectroscopy and the local current–voltage curves of the scanning tunneling spectroscopic measurements illustrate that electrons are predominantly emitted from the grain boundaries. Transmission electron microscopy examinations reveal that the implanted Pt-ions first formed Pt nanoparticles in the UNCD films and then catalytically induced the formation of a nanographitic phase at the grain boundaries during the annealing process. Consequently, the formation of Pt nanoparticles induced abundant nanographitic phases in the Pt-ion implanted/annealed UNCD films, which is believed to be the genuine factor that results in the high electrical conductivity and excellent FEE properties of the films.