Composite Contacts in Microsystems: Fabrication of Metal-Nanostructured Titania Nanocomposites
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J18.21.1
Composite Contacts in Microsystems: Fabrication of Metal-Nanostructured Titania Nanocomposites Abu Samah Zuruzi1, Marcus S. Ward1, Chang Song Ding2, and Noel C. MacDonald1,2 1
Materials Department, University of California, Santa Barbara, CA 93106, USA. Mechanical and Environmental Engineering Department, University of California, Santa Barbara, CA 93106, USA. 2
ABSTRACT Integrated micrometer scale interpenetrating Au-Nanostructured TiO2 (NST) network nanocomposites have been fabricated using a two step process. First, NST pad arrays were prepared by reacting Ti surfaces, patterned with an SiO2 masking layer, with aqueous H2O2. NST formed is porous with pores 50 to 200 nm in diameter and walls about 75 to 125 nm thick. Second, Au was infiltrated into pores of NST using electroless deposition to form the nanocomposite. SEM studies indicate that Au was deposited into pores of NST with little void formation. Selective deposition of Au on NST pads was confirmed using XRD and area-mode XPS. This process is a general route to forming micrometer-scale nanocomposite features consisting of NST and metals that are amenable to electroless deposition. INTRODUCTION Nanocomposites are materials in which at least one of the phases has constituents less than 100 nm in size [1]. An interpenetrating network composite is one in which each constituent phase is continuous and interpenetrating throughout the microstructure [2]. Previous reports of interpenetrating network nanocomposites are largely limited to organic-organic [3] and organic-inorganic material systems [4]. Prior work in metalceramic material systems involve micrometer-scale phases and hence, by definition, may not be classified as nanocomposites [5]. Au-TiO2 interpenetrating network nanocomposites are expected to have the functionalities of its constituents such as the wear resistance of TiO2 together with the high electrical conductivity of Au [2]. Thin films of Au and its alloy have been widely used as contact material in micro-switch devices because of their low-resistivity and oxidation resistance [6]. However, they suffer from wear and stiction which shorten device lifetimes [7]. In contrast, titania films formed using sol-gel processes have excellent wear resistance [8]. Presently, there are no prior reports on the fabrication of patterned micrometer scale metal-TiO2 interpenetrating network nanocomposites. Here, we demonstrate a novel technique to form patterned features of an interpenetrating network nanocomposite of Au and nanostructured TiO2 (NST), suitable for microsystems applications. EXPERIMENTAL DETAILS Fabrication of interpenetrating Au-NST network nanocomposites involves two main steps – firstly, forming porous NST patterns and, secondly, infiltrating NST patterns with Au using electroless deposition. Au was infiltrated into pores of the NST using selective electroless deposition. Commercially available electroless gold plating solution,
J18.21.2
based on alkaline gold cyanide complex with disodium ethylenediaminetetraacetate (Na2EDTA) as c
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