Growth of ZnO nanostructures on metallic and semiconducting substrates by pulsed laser deposition technique

ZnO nanostructures were fabricated on metallic and semiconducting substrates by the pulsed laser deposition technique. Nanoneedles having tips of ∼20-50 nm and roots of ∼50-100 nm, nanowires with a diameter of 50-70 nm and a length of 5-10 νm and flowers of diameters 1-3 νm with the base of leaves around 150-200 nm were obtained on Si, W and rough Cu substrates, respectively. Growth of nanostructures was explained on the basis of the island growth mechanism. Raman spectroscopy showed that all first order optical normal modes of nanostructured ZnO on W and Cu substrates confirmed the wurtzite structure. Nanoneedles grown on the Si substrate exhibited the absence of two normal modes of A₁(LO) and E₁(LO) suggesting weak deviation from the wurtzite structure. The field emission from nanoflowers prepared on the Cu substrate exhibited a current density of 1 mA cm^-2 at an applied field of 7.2 V νm^-1 at ambient temperature, suggesting its utility for flat panel display devices.