Pulsed laser deposited nanostructured InN thin films as field emitters

InN thin films were deposited on c-cut Al2O3 substrates using the DC plasma assisted pulsed laser deposition technique. X-ray diffraction (XRD) studies showed the single phase, polycrystalline nature of the InN thin films with wurtzite structure. Surface morphology of the films, as seen by atomic force microscopy (AFM), consisted of densely packed nanocrystalline grains of InN. The rms value of surface roughness was found to be ∼35 nm. AFM images also revealed the hexagonal features with sharp edges and protrusions of InN. The field emission characteristics of InN/Al2O3 were investigated in ultra high vacuum (1×10−8 Torr) using the diode configuration. The turn-on field, required to draw an emission current density of 10 μA/cm2, was observed to be ∼3.5 V/μm. The maximum emission current density obtained was 230 μA/cm2 when the applied electric field strength was ∼4 V/μm. The Fowler-Nordheim (FN) plot obtained from the current-voltage characteristic was found to be linear in accordance with the quantum mechanical tunneling phenomenon. The field enhancement factor, β, estimated from the slope of the FN plot was 21,167 cm-1. To the best of our knowledge this is the first report of field emission studies of InN/Al2O3 with such high values of β, which is comparable to that obtained for GaN or IrO2.