Study of optical properties of some sol–gel derived films of ZnO

• Published in: Solar energy materials and solar cells Vol. 71; no. 1; pp. 103 - 113
• Main Authors: Bandyopadhyay, S., Paul, G.K., Sen, S.K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2002; Elsevier
• Subjects: Aluminum; Band gap; Band tail; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Doping (additives); Energy gap; Exact sciences and technology; Ii-vi semiconductors; Light absorption; Light transmission; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Physics; Porosity; Refractive index; Sol-gel; Sol-gels; Zinc compounds; Band tail; Band gap; Porosity; Sol-gel; Inorganic compounds; Films; Refractive index; Transition element compounds; Doping; Oxides; Experimental study; Absorption coefficients; Extinction index; Zinc oxides; Energy gap; II-VI semiconductors; Optical transmission; Optical properties; Aluminium additions; Crystal growth from solutions; Optical reflection; Transparent material; Sol-gel process
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/S0927-0248(01)00047-2

The optical transmission and reflection data for aluminum doped zinc oxide films have been analyzed. The optical absorption coefficient ( α) and hence the refractive index ( n), extinction coefficient ( k) and the band gap ( E g) have been determined for these films using different methods. The films are prepared by sol–gel technique and are optically transparent. It is observed that the band gap increases with aluminum doping from 3.19 to 3.24 eV, but is less than the bulk ZnO crystal. A qualitative explanation has been put forward for the band gap widening with doping. The width of the band tail states which is connected to localized states in the band gap is least for 1 at% doped aluminum film. The porosity of the films as deduced from the refractive index seems to be of the same order in all the cases, but relatively higher for 1 at% aluminum doped films.