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

The evolution of the characteristics of diamond films in bias-enhanced-nucleation and bias-enhanced-growth (BEN–BEG) processes was systematically investigated. While the BEN process efficiently formed diamond nuclei on the Si-substrates, BEG with large enough applied field (>− 400 V) and for sufficient long period (> 60 min) induced the development of the nano-grain granular structure with proper crystallinity for the diamond films that enhanced the EFE properties of the films. The EFE process can be turned on at a field as small as 3.6 V/μm, attaining an EFE current density as large as 325 μA/cm2 at an applied field of 15 V/μm for the diamond films, which were BEG under − 400 V for 60 min after BEN (10 min). Such an EFE behavior is even better than that of the ultrananocrystalline diamond films grown in CH4/Ar plasma. Transmission electron microscopic studies revealed that the prime factor that enhanced the EFE properties of these films was the induction of the nanographitic filaments along the thickness of the films that facilitated the transport of electron through the films.

► The evolution of diamond characteristics in BEN–BEG processes was investigated.
► BEG developed nano-grain granular structure with enhanced the EFE properties.
► The EFE process can be turned on at E0 = 3.6 V/μm, with Je = 325 μA/cm2.
► The prime factor is the induction of the nanographitic filaments.