XPS and NEXAFS studies of rare-earth doped amorphous sol-gel films

Information about the structural environment of rare-earth (RE) ions in different host matrices is necessary in order to select a glass composition with optimized spectral properties for integrated optic devices, such as lasers or amplifiers. The present study is aimed at determining the influence of co-dopant elements (P and Al) on the structural environment around (RE) cations (Nd3+ and Er3+) in amorphous silica-titania matrices. For this purpose, thin film samples in the SiO2-TiO2-P2O5-Nd2O3 and SiO2-TiO2-Al2O3-Er2O3 systems were prepared by sol-gel processing and studied by Xray photoemission spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS), after being densified at 900 degrees C. These measurements allowed the determination of the concentrations of the different types of oxygen atoms present in the Si-O-Ti, Si-O-P and Si-O-Al bonding sequences and these were found to reach maximum total values for compositions containing similar to 10 mol% of the PO2.5 or AlO1.5 co-dopants. (C) 1998 Elsevier Science B.V. All rights reserved.