Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5362542 | Applied Surface Science | 2009 | 6 Pages |
ZnO thin films are prepared on glass substrates by pulsed filtered cathodic vacuum arc deposition (PFCVAD) at room temperature. Optical parameters such as optical transmittance, reflectance, band tail, dielectric coefficient, refractive index, energy band gap have been studied, discussed and correlated to the changes with film thickness. Kramers-Kronig and dispersion relations were employed to determine the complex refractive index and dielectric constants using reflection data in the ultraviolet-visible-near infrared regions. Films with optical transmittance above 90% in the visible range were prepared at pressure of 6.5Â ÃÂ 10â4Â Torr. XRD analysis revealed that all films had a strong ZnO (0Â 0Â 2) peak, indicating c-axis orientation. The crystal grain size increased from 14.97Â nm to 22.53Â nm as the film thickness increased from 139Â nm to 427Â nm, however no significant change was observed in interplanar distance and crystal lattice constant. Optical energy gap decreased from 3.21Â eV to 3.19Â eV with increasing the thickness. The transmission in UV region decreased with the increase of film thickness. The refractive index, Urbach tail and real part of complex dielectric constant decreased as the film thickness increased. Oscillator energy of as-deposited films increased from 3.49Â eV to 4.78Â eV as the thickness increased.