Electron Field Emission from Graphitic Nanoflakes Grown Over Vertically Aligned Carbon Nanotubes

Single step growth of self-assembled graphitic nanoflakes (GNF) over carbon nanotubes (CNT) on iron coated silicon(100) substrates is reported. These nanostructures were grown by varying the deposition time in a microwave plasma enhanced chemical vapor deposition reactor using acetylene, hydrogen and argon as reactant gases. Scanning electron microscope (SEM) studies of the deposited carbon films revealed that with increase in deposition time from 3 minutes to 6 minutes, the surface topography of the films transformed from one dimensional cylindrical nanostructure to flat-shaped two-dimensional nanoflakes. Carbon film deposited for 5 minutes showed improved surface coverage as compared to films deposited for 6 minutes i.e., surface area of the CNT film covered with nanoflakes increased as compared to carbon film deposited for higher durations. Field emission studies of films deposited at 5 minutes and 6 minutes showed increase in turn-on field, required for electron emission, from 2.7 V/mu m to 2.9 V/mu m respectively. However, such a combination of one dimension carbon and two dimension carbon may prove useful in applications where high surface area films are required.