Er3+-doped SiO2-Al2O3 thin films prepared by the sol-gel route

The synthesis of homogeneous and pure silica-alumina binary glasses doped with rare-earth (RE) ions such as Er3+ is currently a key challenge for the development of integrated optics devices such as lasers, optical amplifiers or waveguides. In this study Er3+-doped SiO2-Al2O3 films were prepared by the sol-gel route. Aluminium sec-butoxide, Al(O-sec-C4H9)(3) (ASB), and tetraethoxysilane, Si(OC2H5)(4) (TEOS), were used as glass oxide precursors, whereas erbium was introduced as Er(NO3)(3). The alumina content in the silica matrix was 10 at.%, while erbium doping ranged between 200 and 5000 ppm. The preparation of the starting sol-gel solution and the layer deposition by a dip-coating procedure were performed in dry-box under nitrogen atmosphere. The obtained films were subsequently annealed in air between 300 and 1000 degreesC. After treatment at 500 degreesC, layers 200 nm thick were obtained. The composition, microstructure and surface morphology of the films were investigated by X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS), glancing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). Crack-free, transparent, high purity films were obtained, characterised by compositional and microstructural homogeneity. (C) 2004 Elsevier B.V. All rights reserved.