Influence of strain/stress on the nonlinear-optical properties of sprayed deposited ZnO:Al thin films
Highlights
► ZnO:Al 3 at.% thin films show a free strain/stress. ► The strain/stress of the films can influence the crystallinity and the THG. ► The higher third order nonlinear optical susceptibility is obtained for a lower strain/stress value.
Introduction
Zinc Oxide (ZnO), as transparent conducting oxide, photoconducting, piezoelectric, and optical waveguide material, shows a wide range of scientific and technological applications [1], [2], [3]. Different technical were used for thin films growth: radio frequency (RF) magnetron sputtering [4], [5], sol–gel [6], pulsed laser deposition [7], MOCVD [8], hydrothermal process [9] spray pyrolysis technique [10] etc. The effect on the structure, morphology and the optical linear properties induced by aluminium as a doping element, has been extensively studied [4], [7], [9], [10]. In this paper, we analysed the effect of stress on the susceptibility value.
Section snippets
Experiments detail
ZnO and ZnO:Al thin films were deposited by spray pyrolysis. The spraying solution was 0.05 M zinc chloride. Aluminium doping was achieved by adding AlCl3 in a concentration of 0, 2, 3 and 5 at.%. The prepared solution was sprayed at rate of 1.5 ml/min onto the clean glass substrates heated at 450 °C using compressed air as carrier gas. The deposited time was 6 min the nozzle was fixed and its diameter was 500 μm. The nozzle to substrate distance was about 40 cm. The crystalline structure was
X-ray diffraction (XRD)
Fig. 1 shows XRD measurements of the undoped and aluminium doped ZnO thin films deposited on glass substrates grown at 450 °C with an atomic concentration of 2 at.%, 3 at.% and 5 at.%. From the results, we can see that all the films are polycrystalline with a hexagonal wurtzite structure. For all the samples, the ZnO (0 0 2) peak (i.e., 2θ = 34.48°) is the only main peak obtained in thin layers, indicating the presence of preferred orientation and no phase corresponding to other oxides was detected. We
Conclusion
Experimental strain/stress of Al doped ZnO, prepared by the spray pyrolysis method, were calculated. A free strain/stress of thin films was obtained for ZnO:Al (3 at.%) thin films. Our results indicate that the strain/stress of the thin layers can influence the third order nonlinear optical susceptibility. The lower strain/stress value leads to a strong third order nonlinear optical susceptibility.
Acknowledgements
This work is supported by integrated action MA/10/228 and the CNRST Morocco.
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