Fabrication of nitrogen-doped ultrananocrystalline diamond nanowire arrays with enhanced field emission and plasma illumination performance

Large-area silicon nanowire arrays (SiNAs) were fabricated via metal catalytic etching technique, in conjunction with the polystyrene spheres lithographic process. The nitrogen-doped ultrananocrystalline diamond (N-2-UNCD) films were coated on thus formed SiNA by using microwave plasma chemical vapor deposition (MPECVD) process. The N-2-UNCD/SiNWs films, which were grown in CH4/N-2 plasma at 700 degrees C, possess markedly better conductivity (sigma(N2-UNCD)=2-3(Omega cm)(-1)) than the conventional c-UNCD/SiNWs films, which were grown in CH4/Ar plasma at around 425 degrees C (sigma(UNCD)=0.01(Omega cm)(-1)). The EFE process of the former materials can be turned on at (E-0)(N2-UNCD)=7.80 V/mu m achieving larger EFE current density of (J(e))(N2-UNCD)=0.67 mA/cm(2) at an applied field of 13.0 V/mu m, whereas that of the latter materials need (E-0)(=UNCD)=18.25 V/mu m to turn on, attaining only (J(e))(UNCD)=0.024 mA/cm(2) at same applied field. While the plasma illumination process can be triggered at around 0.21 V/mu m, regardless of the characteristics of the cathod materials, plasma illumination intensity/current density is larger when the materials with better EFE properties were used as cathodes for the plasma device. The plasma illumination current density is around (J(pi))(N2-UNCD)=5.0 mA/cm(2) (at an applied field of 0.35 V/mu m) when N-2-UNCD/SiNWs film was used as cathode, whereas the (J(pi))(UNCD)=3.2 mA/cm(2) when the conventional UNCD/SiNWs film was used as cathode. In summary, it is observed that the plasma illumination charateristics of the CP-devices is closely correlated with the electron field emission behavior of the cathode materials, which, in turn, was enhanced due to the improvement in conductivity of the UNCD films.