R. Palomino¹. A. Mendoza-Galván², G. Martínez³, R. Rodríguez-Talavera⁴ and V. M. Castaño^{4 1}Facultad de Ciencias Físico-Matemáticas, Benemérita Universidad Autónoma de Puebla. Av. San Claudio y Río Verde, San Manuel, 72570, Puebla, Pue., México. ²Laboratorio de Investigación en Materiales, CINVESTAV-IPN, Unidad Querétaro, Apdo. Postal 1-798, 76001 Querétaro, Qro., México. ³Instituto de Física, Benemérita Universidad Autónoma de Puebla. Apdo. Postal J-48, 72570, Puebla, Pue. México. ⁴Instituto de Física, Universidad Nacional Autónoma de México, Apdo. Postal 1-1010, 76001, Querétaro, Qro. México.

Amorphous TiO₂ thin films Er⁺³ doped at several concentrations were prepared using the dipping sol-gel method. Silicon wafers and glass slides were used as substrates. The optical characterization includes spectroscopic ellipsometry, optical absorption, and photoluminescence measurements. From the ellipsometry spectra, the effective dielectric function of the doped films was obtained using the Forouhi-Bloomer expressions for amorphous materials. Variations of the optical constants with erbium concentration and substrate are discussed. The optical band gap obtained from the optical measurements is compared with the parameter accounting for it in the Fotouhi-Bloomer model used for the analysis of the ellipsometry spectra. A photoluminescence band below the band gap is observed, its origin is discussed.