TEM and HREM of diamond crystals grown on Si tips: structure and results of ion-beam-treatment

Diamond single crystals were grown on the silicon whiskers by a hot filament chemical vapor deposition technique at the filament temperature about 2100 °C and the temperature of support 800 °C. Specimens were examined by SEM, TEM, HRTEM and SAED. When the filament temperature was about 1900 °C globular polycrystalline diamond particles were grown. At a support temperature more then 800 °C SiC nanoparticles were formed. To investigate the ion etching process of the silicon tip/diamond system, tips were treated with an Ar+ beam with energy up to 30 kV. The results depend on fluence: at 4×1018 ion/cm2 diamonds and partially Si tips were destroyed, amorphous layer was formed (sometimes with nanometric size fragments of diamond); at 1×1018 ion/cm2 sharpened diamonds (radius of curvature about 20 nm) covered with amorphous layer (radius about 80 nm) probably with nanoclusters of diamond were observed; at 4.4×1017 ion/cm2 there was no visible tip sharpening but formation of amorphous thick layer occurred. The emission characteristics of Si tips covered with diamond were improved due to ion treatment. Since such tips in our case were covered with amorphous layer containing nanometric size fragments of diamond, we suppose this layer is responsible for electron emission improvement.