Effect of PLD growth atmosphere on the physical properties of ZnO:Zn thin films

Highly preferential c-axis (002) orientated ZnO:Zn films were successfully prepared in different growth atmospheres using the pulsed laser deposition technique. The stress parameters in the films were determined as −2.81 GPa, −1.03 GPa and −0.08 GPa for the thin films deposited in O₂, Ar and vacuum, respectively. X-ray photoelectron spectroscopy (XPS) high resolution spectra of the Zn-2p peak confirmed that Zn atoms were in a doubly ionized state, and the deconvolution of the O-1s XPS peak showed the presence of oxygen related defects in the films. The surface of the film prepared in Ar was the most rough, while the surface of the films deposited in vacuum and O₂ were relatively smooth. All the films exhibited ultraviolet emission around 378 nm with different intensities. The film prepared in Ar showed a weak deep level emission around 550 nm which was an indication of the low defect concentration in the film. The film prepared in O₂ exhibited yellow emission centered at 600 nm, which XPS results showed to be due to the oxygen related defects. The film obtained in vacuum had a blue and green emission at 405 nm and 512 nm, respectively. The formation of the defects-related visible emission in the different atmosphere was discussed. A good agreement with the theoretical results was obtained, oxygen interstitial and oxygen vacancies were the defects that were responsible for the visible emission around 600 nm and 500 nm–550 nm, respectively. Different from previous papers is the fact that the defects and therefor the defect emission in the thin films could be controlled by using different growth atmospheres to prepare the thin films.