The effects of the oxygen partial pressure, substrate temperature and laser wavelength on the structural and optical properties of thin films of ZnO grown on silicon and glass substrates by pulsed laser deposition have been studied. Regardless of thickness, all the grown layers are caxis oriented and optically transparent. At substrate temperatures as low as 3OO"C, featureless layers with a FWHM value for the (002) XRD reflection less than 0.18" and exhibiting an optical transmission higher than 80% in the visible region were produced. For otherwise identical deposition conditions, the KrF excimer laser (at 248 nm) was always found to produce better quality thin films than the frequency-doubled Nd:YAG laser (532 nm). This is explained by the large difference between the optical absorption coefficients of ZnO at the two wavelengths employed, which play a key role in the laser-target interaction. SEM investigation of the target surface after deposition revealed very different surface morphologies for the two wavelengths employed supporting this assumption.

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Transparent, electrically conductive and c-axis oriented ZnO thin films have been grown by the pulsed laser deposition (PLD) technique on silicon and Coming glass substrates employing either a KrF excimer laser (3. = 248 nm) or a frequency-doubled Nd:YAG laser (3. = 532 rim). The crystalline structure, surface morphology, optical and electrical properties of the deposited films were found to depend not only on the substrate temperature and oxygen partial pressure, but also on the irradiation conditions. The quality of the ZnO layers grown by the shorter wavelength laser was always better than that of the layers grown by the longer wavelength, under otherwise identical deposition conditions. This behaviour was qualitatively accounted for by the results of the numerical solution of a one-dimensional heat diffusion equation which indicated a strong superheating effect of the melted target material for the case of frequency-doubled Nd:YAG laser irradiations. By optimizing the deposition conditions we have grown, employing the KrF laser, very smooth c-axis oriented ZnO films having a full-width at half-maximum value of the (002) X-ray diffraction value less than 0.16 ° and optical transmittance around 85% in the visible region of the spectrum at a substrate temperature of only 300°C.