Optical properties of ZnO related to the dc sputtering power
Department of Physical Sciences, Jordan University of Science & Technology, P.O. Box 3030, Irbid, 22110, Jordan
Revised: 14 June 2006
Published online: 6 July 2006
Zinc oxide thin films were sputter deposited on (100) silicon substrates at 250 ○C substrates temperature via reactive unbalanced dc magnetron process using pure zinc target and argon/oxygen gases. The influence of the applied dc sputtering power (between 100 to 250 Watts, step 50 Watts) on the optical properties of the grown films was systematically investigated by variable angle of incidence spectroscopic ellipsometry (VASE) technique. The refractive indices were found to follow the second-order Sellmeier dispersion relation. However, Cauchy-like dispersion model was formulated to account for the absorption tail and excitonic structure near the direct band gap. The optical properties such as refractive indices, extinction coefficients, optical band gaps, Urbach's energies, excitonic binding structure and absorption coefficients of the grown films were reported as a function of dc power in the photon energy range between 1.2 eV and 4.2 eV. The films were found to be polycrystalline with (002) preferred orientation.
PACS: 78.20.Ci – Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity) / 81.15.Cd – Deposition by sputtering / 81.40.Tv – Optical and dielectric properties (related to treatment conditions)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2006