Bias-enhanced nucleation and growth processes for improving the electron field emission properties of diamond films

The evolution of diamond films in bias-enhanced-nucleation (BEN) and bias-enhanced-growth (BEG) processes was systematically investigated. While the BEN process can efficiently form diamond nuclei on the Si substrates, BEG with large enough applied field (> –400 V) and for sufficiently long periods (>60 min) was needed to develop proper granular structure for the diamond films so as to enhance the electron field emission (EFE) properties of the films. For the films BEG under -400 V for 60 min (after BEN for 10 min), the EFE process can be turned on at a field as small as 3.6 V/μm, attaining a EFE current density as large as 325 μA/cm² at an applied field of 15 V/μm. Such an EFE behavior is even better than that of the ultrananocrystalline diamond films grown in CH4/Ar plasma. Transmission electron microscopic examination reveals that the prime factor enhancing the EFE properties of these films is the induction of the nano-graphite filaments along the thickness of the films that facilitates the transport of electrons through the films.