Metallic phase formation in oxide films Paul W. Wang a, * , Jin-Cherng Hsu b , Luu-Gen Hwa b a Department of Physics, Bradley University, Peoria, IL 61625, USA b Department of Physics, Fu-Jen Catholic University, Taipei 24205, Taiwan, ROC Abstract Metallic particles embedded in the oxide film play an important role in film’s optical property. In this paper it is demonstrated that metallic phases of Ag, Ti, and Pb, can be formed in different oxide films under heating, X-ray photon, and electron radiation. The metal- lic phase separated from metal oxide film was investigated by X-ray photoelectron spectroscopy technique. Metal oxygen bond breaking and total energy reduction in the film result in the formation of metal in the film. It is necessary to fully understand the formation mech- anism of metallic particles so their shapes and distributions can be tailored to achieve the desired film’s properties. Ó 2007 Elsevier B.V. All rights reserved. PACS: 61.82.Ms; 61.43.Fs; 68.35.Md; 82.80.Pv Keywords: Diffusion and transport; Radiation effects; Atomic force and scanning tunneling microscopy; Oxide glasses; Radiation; Thermal properties; XPS 1. Introduction Nanophase metallic particles dispersed in thin oxide films control the optical properties of the film [1]. Faraday recognized that color of gold ruby glass caused by fine gold particles dissolved in glass network during rapid cooling [2]. Confined nanophase metallic particles in the glass insu- lator have quantized energy levels depending on the size and shape of nanoparticles and therefore they posses inter- esting optical, magnetic and other properties [3]. In this paper, X-ray photoelectron spectroscopy (XPS) is used to monitor the formation of metallic Ag, Ti, and Pb in silver ion-exchange soda–lime glasses, TiO 2 films co-sputtered by Al, and lead silicate glasses. The separation of the metallic phase from glass environment was triggered by heating and irradiation. It is of interest to deduce the best treatment conditions in order to have uniformly distributed, small but same shape metallic particles in the glasses so the opti- mum desired film properties can be achieved. 2. Experimental procedure 2.1. Thermally activated metallic phase formation In the first case [4], metallic Ag separated from silver ion-exchange soda–lime glasses, samples were prepared by dipping commercially available soda–lime glass into a molten silver nitrate at 450 °C. Then the samples were loaded into a ultrahigh vacuum chamber equipped with XPS surface analysis technique and heated in the range of 20 to 450 °C inside the chamber where XPS spectra were collected in situ at various sample temperatures. In the second case, titanium dioxide (TiO 2 ) films co- sputtered by different concentrations of aluminum (Al) using ion beam sputtering deposition (IBSD) technique were investigated. Oxygen used as a working gas was fed near the glass substrate (Corning 7059) and regulated at 2.6 · 10 3 Pa by a needle valve. Specimens were labeled by Al-R, where R was the area ratio of Al to Ti target in 0022-3093/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2006.10.080 * Corresponding author. Tel.: +1 11309 677 3003/693 1612; fax: +1 11309 677 2999. E-mail address: pwang@bradley.edu (P.W. Wang). www.elsevier.com/locate/jnoncrysol Available online at www.sciencedirect.com Journal of Non-Crystalline Solids 354 (2008) 1256–1262