AVS 47th International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuP

Paper TF-TuP25
Optical and Structural Properties of Sol-gel SiO@sub 2@ Layers Containing Cobalt

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: A. Mendoza-Galván, CINVESTAV-IPN, México
Authors: A. Ramos-Mendoza, CINVESTAV-IPN, México
H. Tototzintle-Huitle, CINVESTAV-IPN, México
A. Mendoza-Galván, CINVESTAV-IPN, México
J. González-Hernández, CINVESTAV-IPN, México
B.S. Chao, Energy Conversion Devices, Inc.
Correspondent: Click to Email
SiO@sub 2@ layers containing cobalt in the range of 2 to 11 percent in volume were prepared using the sol-gel method. The layers with a thickness of about 600 nm were heat treated in air at 300 and 500 °C. Their structure and optical properties were characterized using optical transmission and reflection measurements, x-ray diffraction and Auger depth profile. The optical transmission data in the UV-visible range, of samples with low cobalt concentrations, show only the absorption bands corresponding to the tetragonal Co, regardless of the heat treatment temperature and the Co concentration. Layers with larger amount of Co, show absorption bands corresponding to both, tetragonal and octahedral Co. When these layers are heat treated, most of the cobalt migrates to the layer surface, being oxidized by the atmospheric oxygen, to form a conducting top layer of Co@sub 3@O@sub 4@, which thickness depends on the heat treatment temperature and Co concentratation. The presence of this top layer has been deduced from optical and Auger depth profile measurements. The cobalt oxide layer thickness ranges from about 100 to 7 nm. In order to describe the absorption bands of both, tetragonal and octahedral Co, it was used the Lorentz oscillator model for the complex effective dielectric function of the SiO@sub 2@ cobalt doped layers. The frequency dependence of the optical constants of the cobalt oxide top layer, in the UV-visible range, was obtained with a generalized Lorentz oscillator model. These latter results are in a good agreement with previous reports.