Laser annealing of zinc oxide thin film deposited by spray-CVD

A polycrystalline ZnO film was deposited on quartz and silicon substrates by a spray-CVD method. The deposited film was annealed by thermal and by laser heating. Both CW CO2 laser and pulsed excimer (XeCl) lasers were used for the purpose. The as-grown film and the annealed film were analysed for crystallinity and compositions by XRD, for surface morphology by SEM, for band gap by optical absorption and for electrical parameters by Van der Pauw and Hall effect measurements. While the excimer laser annealing improved the crystallinity with higher laser power density, CW CO2 laser incorporated the crystallinity only at low power. High power CO2 laser annealing damaged the ZnO surface with the creation of more defects. This was verified by SEM morphology studies. There was no change in band gap which ensures no formation of any other phase in ZnO due to annealing effects. The increase in resistivity both by thermal and pulsed laser annealing was confirmed by Van der Panw resistivity measurements. The majority carrier concentration and mobility were determined by Hall effect measurements.