Metal-Alloy Nanocluster Formation in Silica Glass by Sequential Ion Implantation
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Metal-Alloy Nanocluster Formation in Silica Glass by Sequential Ion Implantation G. Battaglin 1, E. Cattaruzza 1, F. Gonella 1, F. D’Acapito 2, C. de Julian Fernandez 3, G. Mattei 3, C. Maurizio 3, P. Mazzoldi 3, C. Sada 3 1 INFM, Dipartimento di Chimica Fisica, Università di Venezia, Dorsoduro 2137, I-30123 Venezia, Italy 2 INFM, ESRF-GILDA CRG, B.P. 220, F-38043 Grenoble, France 3 INFM, Dipartimento di Fisica, Università di Padova, via Marzolo 8, I-35131 Padova, Italy
ABSTRACT Sequential ion implantation of two metal species in silica glass may give rise to the formation of alloy metal nanoclusters. Composite materials with peculiar optical properties can be therefore fabricated, with application in integrated-optical devices. In the presented experiments, different couples of transition elements were sequentially implanted in a silica glass. The resulting systems, in some cases after annealing in either reducing or oxidizing atmosphere, were studied by several analytical techniques, such as transmission electron microscopy and X-ray absorption spectroscopy. The formation of different alloy nanoclusters was evidenced, together with the cluster crystalline structure and the chemical environment of the dopant species.
INTRODUCTION Metal nanocluster composite glasses (MNCGs) are formed by nanometer-sized crystalline metal clusters embedded in a glass matrix [1]. Third-order optical nonlinearity as well as magnetic properties [2] are expected to play a role in the exploitation of MNCGbased devices, so both basic and applied issues are presently the subject of MNCG research, in terms of physics and chemistry of cluster formation, structure and properties, as well as the cluster-matrix interaction. Ion implantation techniques are suitable for promoting the cluster formation in glass [3] with a partial control on the size distribution. Moreover, sequential ion implantation of two metal species in silica has been observed to form different metal cluster structures [4,5], for example, core-shell or alloys. The physical mechanisms governing the cluster formation have not been clarified yet, even for single metal implants. Chemical reactivity of the species as well as defect formation affect the cluster structure [6,7], and the thermodynamic-based models that predict the possible resulting aggregate are only partially effective [8]. However, silica-based MNCGs are particularly attractive, owing to their transparency in the optical fiber transmission window [9]. In this work, we present a short overview on a series of experiments, realized to study MNCGs formation in fused silica glass upon sequential ion implantation of pairs of transition metals. After implantation, samples were annealed at a temperature lower than the softening point of the glass in different (either reducing or oxidizing) atmospheres. The samples were then studied by transmission electron microscopy (TEM), selected-area electron diffraction (SAED) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Samples were also characterized by other
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