Pulsed laser deposited Ga doped ZnO/SiO_x/Si(100) thin films and their field emission behavior

摘要

Pulsed laser deposition was used for growing undoped ZnO and Ga (3 and 5 at. wt.%) doped ZnO thin films on Si (100) substrates with native oxide. X-ray diffraction studies reveal highly c-axis oriented, single phase growth of wurtzite ZnO and Ga doped ZnO thin films. X-ray photoelectron spectroscopy study shows that gallium exists in the Ga~(3+) oxidation state replacing Zn~(2+) in the ZnO matrix. It, hence, acts as a donor, increasing the charge carrier density, which was confirmed by Hall measurement. Significant change in the surface morphology of the thin films, such as increased surface roughness, presence of nanostructures, was observed in the Ga doped ZnO thin films. Surface morphology was also influenced by the Ga doping concentration. Higher charge carrier density with the modified surface morphology vindicated its use for field emission studies. Reduction in the threshold field defined for obtaining an emission current density of 0.1 μA/cm~2, increased field enhancement factor are features of Ga doped ZnO thin films. The stability of field emission current density of the undoped ZnO and Ga doped ZnO thin films was studied at the preset current density of 2.5 and 2.0 μA/cm~2 respectively, for two and half hours.