Nanostructured Ceramic Film Formation on Self-Assembled Monolayers via a Biomimetic Approach
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0901-Ra21-06.1
Nanostructured Ceramic Film Formation on Self-Assembled Monolayers via a Biomimetic Approach Guangneng Zhang1, Douglas A. Bolm2, Dorothy W. Coffey2, Lawrence F. Allard2 and Junghyun Cho1 1 Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, NY 13902, U.S.A. 2 Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S.A. ABSTRACT A biomimetic approach is employed to deposit ceramic films on organic self-assembled monolayers (SAMs) coated substrates. Specifically, zirconia (ZrO2) films are grown in a zirconium sulfate precursor solution at near room temperatures (~70˚C). This process, directed by the nanoscale organic template, mimics the controlled nucleation and growth of the biominerals such as bones and teeth. The resultant zirconia films consist of nanosized particles (5-10 nm) that are precipitated out in a supersaturated precursor solution. Cross-sectional TEM and STEM works were performed to quantitatively analyze the film structure and chemistry, as well as interfacial region of the ceramic-SAM films. A stepwise deposition process was developed to avoid excessive formation of aggregation. Further, the dynamic nanoindentation testing was employed to assess the thickness and film-only intrinsic mechanical properties for direct comparison among the films processed with different processing parameters and microstructures. The films with finer particulate structure displayed higher intrinsic modulus than did those with coarser structure. INTRODUCTION Ceramic thin films have been suggested as a hermetic packaging alternative for microelectromechanical system (MEMS), microelectronics, and sensors in harsh and corrosive environments. A major challenge to produce ceramic thin films is to find a low-temperature synthetic route, as well as to possess microstructures that can accommodate the mechanical and thermal stresses. Interestingly, the best example of controlled ceramic formation is routinely observed in nature. A few specific examples include eggshells, teeth, bones, and kidney stones whose growth, morphology, and composition are directed by organic matrices. In light of the natural biomineralization process, researchers have developed a promising biomimetic deposition approach in which self-assembled monolayers (SAMs) are employed as an organic template onto which ceramic thin films can be grown through hydrolysis of a precursor solution at near room temperature [1-3]. Thin films of ZrO2 [3], Y2O3-doped ZrO2 [1], Y2O3 [4], SnO2 [5], ZnO [6], TiO2 [7], and V2O5 [8] have thus far been prepared using this technique. In this study, zirconium oxide films were formed on the SAM-coated silicon wafers through the hydrolysis of zirconium sulfate (Zr(SO4)2·4H2O) solutions in acid environment at 70°C. One purpose of this study is to develop a bilayer structure that employs the advantages of organic SAM while processing hard and stiff ceramic protective films. We herein report the synthesis of the ZrO2/SAM bilayer films and corresponding na
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