Growth behavior of nanocrystalline diamond films on uitrananocrystailine diamond nuclei: The transmission electron microscopy studies

摘要

Micron-crystalline diamond (MCD) films with a unique microstructure were synthesized using a modified nucleation and growth process, in which a thin layer of uitrananocrystailine diamond (UNCD) was used as nucleation layer for growing diamond films in H_2-plasma. Thus obtained (MCD)_(UNCD) diamond films consist of nanosized diamond clusters (-10 nm in size) surrounding the large diamond grains (～300 nm in size), exhibiting better electron field emission (EFE) properties than the conventional diamond materials with faceted grains. The EFE of these (MCD)(UNCD) films can be turned on at E_0-11.1 V/μm, achieving EFE current density as large as (J_e)=0.7 mA/cm~2 at 25 V/μm applied field, which can be attributed to the presence of large proportion of UNCD grains lying in between the MCD grains, forming an electron conduction path and thus facilitating the EFE process. Transmission electron microscopy examinations reveal that such a unique microstructure was formed by agglomeration and coalescence of the nanosized UNCD grains.