Electrical and Optical Properties of Self-Assembled, Ordered Gold Nanocrystal/Silica Thin Films Prepared by Sol-Gel Proc
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Electrical and Optical Properties of Self-Assembled, Ordered Gold Nanocrystal/Silica Thin Films Prepared by Sol-Gel Processing Kai Yang1, Hongyou Fan2,3, Michael J. O’Brien1, Sima La Fontaine1, Gabriel P. Lopez2, Kevin J. Malloy1, C. Jeffrey Brinker2,4, and Thomas W. Sigmon1 1 Center for High Technology Materials, 2Department of Chemical and Nuclear Engineering, the University of New Mexico, Albuquerque, NM 87106 3 Ceramic Processing and Inorganic Materials Dept., 4 Self-Assembled Materials Dept., Advanced Materials Laboratory, Sandia National Laboratories, Albuquerque, NM 87106 ABSTRACT Highly ordered gold NC/silica films are synthesized by self-assembly of water-soluble gold nanocrystal micelles and soluble silica using a sol-gel spin-coating technique. The optical properties are analyzed using ellipsometry and ultraviolet-visible spectroscopy. The absorption spectra show a strong surface plasmon absorption band at ~520 nm for all samples. Angular excitation spectra of the surface plasmon show a steep dip in the reflectivity curve at ~65°. Charge transport behavior of the films is examined using metal-oxide-semiconductor (MOS) structures. MOS capacitor samples exhibit charge storage with discharge behavior dominated by electron transport within the gold NC arrays.
INTRODUCTION Nanometer-sized crystallites of metals, semiconductors, and oxides form a new class of “artificial solids” possessing electrical properties far different from those of either the corresponding isolated atoms or macroscopic solids[1-4]. The ability to adjust the properties of such solids through control of the size, shape, composition, crystallinity, and structure of the crystallites leads to a wide range of potential applications. For instance, memory-cell structures employing metal nanocrystals (NC) as the charge storage media have been under investigation as promising candidates for replacing conventional DRAM or flash memories [5,6]. Recently, we demonstrated direct synthesis of water-soluble nanocrystalline gold micelles, including their selfassembly with silica into robust, ordered, nanocrystalline arrays in bulk or thin film forms [1,7]. These ordered arrays of metallic nanocrystals are potential implementations of several types of model systems including the nanocrystal memory devices mentioned above [6]. In this work, we report the electrical and optical properties of highly ordered gold NC/silica films. The films are synthesized through self-assembly of water-soluble gold NC micelles and soluble silica by sol-gel processing. Their optical properties are analyzed with ellipsometry and ultraviolet(UV)-visible spectroscopy. The absorption spectra show a strong surface plasmon resonance (SPR) absorption at ~520 nm for all samples. Angular excitation spectra of surface plasmon show a steep dip in the reflectivity curve at ~65°. Charge transport behavior of the films was examined using metal-oxide-semiconductor (MOS) structures. MOS capacitor samples exhibit charge storage with discharge behavior dominated by electron transport w
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