Radiation Enhanced Diffusion in Ion-Implanted Glasses and Glass/Metal Couples
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RADIATION ENHANCED DIFFUSION IN ION-IMPLANTED GLASSES AND GLASS/METAL COUPLES*
G. W. ARNOLD Sandia National Laboratories,
Albuquerque,
NM
87185
ABSTRACT Ion implantation causes alkali migration to the surface in alkali silicate glasses. Rutherford backscattering spectrometry was used to follow 1 6this depletion. 2 250 key Xe/cm 5x10 of implantations Room temperature in 12M2 0o88SiO2 (M = Li,Na,K,Rb,Cs) removes approximately equal numbers (within a factor of 2) of alkali from the glass. Low temperature (77K) implants significantly reduce the alkali loss. These results imply a radiationenhanced diffusion mechanism in which the alkali interchanges with the products of the collision cascade, with the kinetics being limited by the radiation damage components. The results for mixed-alkali glasses ((12-x)M 2 0. xCs 2 0.88Si0 2 ) give further evidence for this process. In glass/metal couples, radiation enhanced diffusion allows the interchange of glass network components with deposited metals. Rutherford backscattering spectrometry was used to follow the interchange of silicate and phosphate glass components with metal ions near the heavy-ion implanted interface between glass substrate and metal (Al,Zr) films.
INTRODUCTION Alkali depletion in alkali-containing glasses subjected to electron or ion bombardment has been noted in many instances (see, e.g., [1-3]). This early work has been reviewed by Carter and Grant[4]. Charged particle irradiation resulted in movement of the alkali ions toward the surface and into the vacuum from a depth roughly corresponding to the depth of penetration of the particle. This effect makes Auger electron spectroscopy (AES) difficult in alkali-containing glasses because of the disappearance of the alkali signal with time due to the electron (0.3-3 keV) analysis beam[5-8]. Alkali mobility can also be a problem in secondary-ion-mass-spectroscopy (SIMS) which use ion-beam milling in order to depth profile elemental concentrations[9]. Rutherford backscattering spectroscopy (RBS), however, allows accurate measurement of the depth-profiles of near-surface alkali because of the higher beam energy (1-3 MeV) and the ability to simultaneously probe in depth without high beam fluence. Ion implantation can alter the near-surface properties of glasses either through the chemical activity of the implanted species or by the implantation damage. Arnold and Borders[10-12] used RBS to demonstrate that heavy ion implantation removed alkali ions from lithia-alumina-silicate glasses in the region of the implanted-ion distribution. Arnold and Peercy[13] used inert gas implantation to bring about low-temperature crystallization of a Li 2 0.2Si0 2 glass. Crystallization occurred because the loss of Li from the implanted region caused this region to be readily phase separable.
*This work performed at Sandia National Laboratories supported by the U. S. Department of Energy under contract #DE-AC04-76DP00789.
Mat. Res.Soc. Symp. Proc. Vol. 27 (1984) @Elsevier science Publishing Co.,
Inc.
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