Optical and Electrical Properties of Metal Nanoclusters Embedded in a Dielectric Medium
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Optical and Electrical Properties of Metal Nanoclusters Embedded in a Dielectric Medium Frédéric Dumas-Bouchiat1, Syed Salman Asad1, Corinne Champeaux1, Alain Catherinot1, Aurelian Crunteanu2 and Pierre Blondy2 1 SPCTS UMR CNRS 6638, 2IRCOM, UMR CNRS 6615, Faculté des Sciences et Techniques, Université de Limoges, 123 av. Albert Thomas, 87060 Limoges Cedex, France ABSTRACT We present the synthesis and optical and electrical characterization of amorphous nanocomposite layers made of metallic nanoclusters embedded in an alumina (Al2O3) matrix (ncM:Al2O3 with M= Ag, Cu and Co). The nanocomposites, obtained by a pulsed laser deposition (PLD)- derived method, exhibit specific optical plasma resonance absorption in the visible and UV region. The position of the absorption peaks depends on the cluster type and gives information about its dimension and nature (metal or oxide). The results fit well with the size and shape distribution recorded by transmission electron microscopy (TEM). Electrical properties and conduction mechanisms of nc-Co:Al2O3 layers were investigated for different doping levels and in temperature range of 303-473 K. It was concluded that space charge limited currents theory (SCLC) can be assumed as major conduction mechanism, at least for intermediate doping levels (~9 vol.%). INTRODUCTION Nanostructured materials are currently considered of great importance for the development of a number of promising technologies in areas like semiconductor physics, optics, chemistry or biology. Therefore, the fabrication and characterization of these materials have focused a high research interest. The non-linear optical and electrical properties of such composites are much larger than those of their bulk counterparts and they can be tuned by controlling the volume fraction and morphology of constituents [1,2]. The choice of the doping nano-particles (metals, ferroelectrics...) and of the doped matrix (insulators, semi-conductors…) influences the properties of the nanostructured compound and its application domain (optics, microelectronics…)[2]. In particular, the optical response of metallic nanoclusters under an electromagnetic excitation is determined by collective oscillations of the free electrons in the particle (described by the term plasma resonance absorption or surface plasmon resonance), specific to their intrinsic characteristics (material, size and shape) and to the host medium [1]. Although the plasma resonance absorption of isolated or matrix-embedded metallic nano-clusters was thoroughly investigated (especially for the noble metals like Au or A) [1, 3 and Refs. therein], less is known about their electrical properties and conduction mechanisms. Our investigations are focused on the fabrication of materials containing metal nano-clusters and their optical and electrical characterization. The fabrication concept is based on generation of nm-sized clusters and their insertion in a thin dielectric layer host (alumina, Al2O3). We developed a PLD-based method for controlled synthesis of nano
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