Nitrogen doping, optical characterization, and electron emission study of diamond

Nitrogen-doped chemical vapor deposited (CVD) diamond films were synthesized with N2 (nitrogen) and C3H6N6 (melamine) as doping sources. More effective substitutional nitrogen doping was achieved with C3H6N6 than with N 2. Since a melamine molecule has an existing cyclic C-N bonded ring, it is expected that the incorporation of nitrogen on substitution diamond lattice should be facilitated. The diamond film doped with N2 contained a significant amount of non-diamond carbon phases. The samples were analyzed by scanning electron microscopy, Raman scattering, photoluminescence spectroscopy, and field emission measurements. The sample produced using N 2 exhibited a lower field emission turn-on field than the sample produced using C3H6N6. It is believed that the presence of the graphitic phases (or amorphous sp2 carbon) at the grain boundaries of the diamond and/or the nanocrystallinity (or microcrystallinity) of the diamond play a significant role in lowering the turn-on field of the film produced using N2. The nature of the nitrogen-related 1190 cm-1 Raman peak was investigated. Nitrogen is incorporated predominantly to the crystalline or amorphous sp2 phases when nitrogen is added to the growing diamond. Field emission characteristics from metallic field emitter coated with type Ia and Ib diamond powders were also investigated. No significant difference in electron emission characteristics were found in these samples. Voltage-dependent field emission energy distribution (V-FEED) measurement was performed to analyze the energy distribution of the emitted electrons. It is believed that substitutional nitrogen doping plays only a minor role in changing field emission characteristics in diamond.; Discontinuous diamond films were deposited on silicon using a microwave plasma chemical vapor deposition (MPCVD) system. The diamond deposits were sharpened by argon ion beam etching. Raman spectroscopy was carried out to study the structural change of the diamond after ion beam bombardment. Field emission measurements were performed in-situ with an electron beam induced current (EBIC) probe inside the chamber of the scanning electron microscope. It was found that amorphous sp2 carbon is produced as the diamond is sputtered by the Ar ion beam. The field emission turn-on field was also significantly lowered after sharpening, which, it is speculated, is caused by field enhancement due to a change in geometry and/or structural changes (such as amorphization of crystalline diamond into graphitic or amorphous sp2 carbon) by Ar ion irradiation.; Secondary electron emission patterning of single crystal diamond surfaces with hydrogen and oxygen plasma treatments was demonstrated. Hydrogen plasma treated regions were much brighter than the oxygen terminated regions. Results of atomic force microscopy confirmed that the observed contrast is not topographical. Several other possible negative electron affinity (or low positive electron affinity) materials such as chemical vapor deposited (CVD) diamond, aluminum nitride and tetrahedrally bonded amorphous carbon [tx a-C 1-x] were also investigated. Faint image contrast (patterning) was also observed from polycrystalline CVD diamond, single crystal aluminum nitride films, and polycrystalline aluminum nitride films; however, no contrast at all was obtained from tetrahedrally bonded amorphous carbon [tx a-C1-x] films.