Structural characterization and field emission of stacked-cone GaN nanorods

The stacked-cone morphology GaN nanorods with diameters of 100–400 nm and lengths of tens of micrometers were synthesized by metal-catalyzed chemical vapor deposition. The stacked-cone GaN nanorods possessed dominated hexagonal crystalline structure with growth direction along [0001]. TEM analysis showed that the top tip had a bicrystal structure of hexagonal and cubic phases, while the stem and side tip had single hexagonal phase. Room temperature field emission test showed the turn-on field was 8.9 V/µm at 0.1 µA/cm2 and current density was about 0.1 mA/cm2 at 14.2 V/µm at a vacuum gap of 70 µm. The field enhancement factor β and anode-cathode gap d follows a universal equation. The simple synthesis method and good emission properties imply their potential application in vacuum microelectronic.