Influence of annealing on optical properties and surface structure of ZnO thin films

• Published in: Journal of crystal growth Vol. 287; no. 1; pp. 105 - 111
• Main Authors: Liu, Y.C., Tung, S.K., Hsieh, J.H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 18.01.2006; Elsevier
• Subjects: A1. Annealing; A1. Optical properties; A1. Surface structure; B1. Zinc oxide; Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Treatment of materials and its effects on microstructure and properties; Vacuum deposition; 68.55.−a; A1. Optical properties; A1. Surface structure; B1. Zinc oxide; 78.20.Ci; 81.40.Tv; A1. Annealing; Atomic force microscopy; Inorganic compounds; Spectroscopic ellipsometry; Refractive index; Crystal growth from vapors; Surface structure; Filtered cathodic vacuum arc deposition; Thin films; Time dependence; Topography; Thermal annealing; 81.40.Tv A1. Annealing; Transition element compounds; Binary compounds; 68.55.-a; Experimental study; Reflectivity; Dielectric function; Zinc oxides; II-VI semiconductors; Morphology; Wide band gap semiconductors; Vacuum deposition
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2005.10.052

Thermal annealing effects on optical properties and surface structure of zinc oxide (ZnO) thin films prepared by filtered cathodic vacuum arc technique were investigated by spectroscopic ellipsometry (SE) and atomic force microscopy (AFM). In the SE study, Cauchy model was used to extract the optical constants of ZnO thin films for photon energies below the band gap while point-by-point fitting was used to determine the optical constants of the films for photon energies above the band gap. The influence of annealing on the optical properties, in the photon energy ranging from 1.1 to 5 eV, has been demonstrated. It was found that the values of the refractive index, the reflectance and the real part of the complex dielectric function decrease with increasing annealing time. On the other hand, tapping mode AFM was used to study the surface structure and topography of ZnO thin films. AFM study revealed that annealing roughened the surface of the films and increased the size of grains on the surface. It was observed that the changes in the optical properties were correlated to the changes in the surface structure as a result of annealing.