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

[[abstract]]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.[[journaltype]]國外[[ispeerreviewed]]Y[[booktype]]紙本[[countrycodes]]US

Modification of ultrananocrystalline diamond film microstructure via Fe-coating and annealing for enhancement of electron field emission properties

[[abstract]]The interaction between Fe-coatings and ultrananocrystalline diamond (UNCD) films during annealing was investigated in detail using transmission electron microscopy. The thin Fe-coating first formed nanosized Fe-clusters and then catalytically dissociated the diamond, re-precipitating carbon to form nanosized graphite clusters. These clusters formed conducting networks that facilitated electron transport and greatly improved the electron field emission (EFE) properties of the UNCD films. The extent of enhancement varied markedly with annealing temperature and atmosphere. For H2-annealed films, EFE behavior was optimized by annealing at 900 °C. EFE was turned on at (E0)H2 = 1.2 V/μm, attaining EFE current density of (Je)H2 = 772.0 μA/cm2 at an applied field of 8.8 V/mm. These characteristics were superior to those of UNCD films NH3-annealed at 850 °C. The inferior EFE properties for the NH3-annealed samples were attributed to reaction of NH3 with the hydrocarbon phase that encapsulated the nanosized diamond grains, hindering Fe–diamond interaction.[[booktype]]紙

Microstructure evolution and the modification of the electron field emission properties of diamond films by gigaelectron volt Au-ion irradiation

[[abstract]]The effect of 2.245 GeV Au-ion irradiation and post-annealing processes on the microstructure and electron field emission (EFE) properties of diamond films was investigated. For the microcrystalline diamond (MCD) films, Au-ion irradiation with a fluence of approximately 8.4×1013 ions/cm2 almost completely suppressed the EFE properties of the films. Post-annealing the Au-ion irradiated MCD films at 1000°C for 1 h effectively restored these properties. In contrast, for ultra-nanocrystalline diamond (UNCD) films, the Au-ion irradiation induced a large improvement in the EFE properties, and the post-annealing process slightly degraded the EFE properties of the films. The resulting EFE behavior was still better than that of pristine UNCD films. TEM examination indicated that the difference in Au-ion irradiation/post-annealing effects on the EFE properties of the MCD and UNCD films is closely related to the different phase transformation process involved. This difference is dependent on the different granular structures of these films. The MCD films with large-grain microstructure contain very few grain boundaries of negligible thickness, whereas the UNCD films with ultra-small-grain granular structure contain abundant grain boundaries of considerable thickness. Au-ion irradiation disintegrated the large grains in the MCD films into small diamond clusters embedded in an amorphous carbon (a-C) matrix that suppressed the EFE properties of the MCD films. In contrast, the Au-ion irradiation insignificantly altered the crystallinity of the grains of the UNCD films but transformed the grain boundary phase into nano-graphite, enhancing the EFE properties. The post-annealing process recrystallized the residual a-C phase into nano-graphites for both films.[[incitationindex]]SCI[[booktype]]電子

The induction of a graphite-like phase by Fe-coating/post-annealing process to improve the electron field emission properties of ultrananocrystalline diamond films

[[journaltype]]國外[[ispeerreviewed]]Y[[booktype]]紙本[[countrycodes]]CH