Dense Plasma Focus Device Based High Growth Rate Room Temperature Synthesis of Nanostructured Zinc Oxide Thin Films

Abstract

High-energy-density plasmas in plasma focus device are now routinely being used as nonconventional plasma nanotechnology tool with novel processing and deposition parameters which are not available in conventional lowtemperature plasma facilities. This paper reports the synthesis of multilayered polycrystalline intrinsic defects-free nanostructured zinc oxide (ZnO) thin film onto room-temperature silicon substrates at high growth rates using pulsed high-energy-density dense plasma focus device. The device was operated in pure oxygen environment and the ablation target used was a pure zinc rod fitted onto the anode top. Thin films of ZnO were deposited at room temperature using different numbers of dense plasma focus shots and at different distances from the anode top. The as-deposited ZnO showed the formation of polycrystalline hexagonal phase ZnO thin films with strong c-axis orientation. The scanning electron microscopy results showed either uniformly laid nanoparticles or cauliflower aggregates of nanoparticles on the surface of the thin-film samples with average nanoparticle size varying between 23.3 ± 6.1 and 69.7 ± 16.5 nm. The average thicknesses of the multilayered thin films were measured to be in a range of 1.06 ± 0.14 to about 2.82 ± 0.32 μm. The complete disappearance of deep level emission band in photoluminescence spectrum of ZnO thin-film sample deposited using 30 focus shots at deposition distance of 15 cm showed successful synthesis of high crystalline quality intrinsic defects-free as-deposited ZnO thin film. One of the key features of the ZnO thin-film synthesis using nonconventional plasma focus device is the very high average growth rate of about 0.1 μm/shot. At one plasma focus shot per minute operation, the average growth rate comes out to be 0.1 μm/min, which is either higher or comparable with commonly used ZnO deposition methods; but at 10 Hz operation extreme growth rates of about 60 μm/min could be achieved.