Field electron emission properties of bulk diamond/expanded graphite composite cathode

Diamond exhibits a negative electron affinity potential and a high thermal conductivity. Nevertheless, the elevated surface resistivity of diamond restricts its utilization in cold cathodes. Expanded graphite, an allotrope of diamond, is a material that exhibits high electrical conductivity and is cost-effective to manufacture. The combination of these two elements into a hybrid structure is a highly desirable proposition, as it would facilitate a synergistic approach to field-emitting materials. In this study, diamond-expanded graphite bulk composite cathodes were prepared using the cold pressing method. The results demonstrate that the cathode comprising diamond particles with a diameter of 0.5 μm and a content of 20% exhibits the most favorable electron emission activity. The turn-on field strength (at 1 mA/cm²) and threshold field strength (at 10 mA/cm²) were 1.61 V/μm and 2.11 V/μm, respectively. The maximum current density and the field enhancement factor reached 911.24 mA/cm² (at 3.77 V/μm) and 4490, respectively.