Facile Fabrication and Integration of Patterned Nanostructured Titania into Microsystems: Effect of Parent Ti Microstruc
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Facile Fabrication and Integration of Patterned Nanostructured Titania into Microsystems: Effect of Parent Ti Microstructure on Kinetics of Reaction Diana M. DeRosa1,2, Abu Samah Zuruzi3, and Noel C. MacDonald3 1
National Nanotechnology Infrastructure Network, University of California, Santa Barbara, CA 93106, USA. 2 Biosystems Engineering Department, and Biochemistry and Molecular Biophysics Department, The University of Arizona, Tucson, AZ 85721, USA. 3 Materials Department and Mechanical and Environmental Engineering Department, University of California, Santa Barbara, CA 93106, USA.
ABSTRACT One promising route to integrate nanostructured titania (NST) into nano/micro electrical mechanical systems (N/MEMS) devices is by reacting Ti films with aqueous hydrogen peroxide (aq. H2O2) solution. However, little is known about the reaction kinetics between aq. H2O2 and Ti thin films. Here, the effect of Ti microstructure and film thickness on kinetics of reaction was investigated. For films less than 50 nm thick, the kinetics is interface-reaction controlled. For thicker films, the reaction is controlled by diffusion through a hydrated titania gel layer. Activation energies of these kinetics were extracted. Pore size of NST is affected by thickness of parent Ti films. Depending on thickness of parent Ti films, NST with average pore sizes ranging from 15 nm to 150 nm was formed. The ability to form integrated porous NST features with controllable pore sizes may have implications on the development of devices for drug delivery and macromolecular separation.
INTRODUCTION Nanostructured titania (NST) is the material of choice for many applications, from drug delivery to energy conversion [1,2]. Various techniques have been proposed to form NST [3-5]. However, methods to integrate NST into nano/micro electrical mechanical systems (N/MEMS) devices are currently lacking. We have recently developed a simple technique to form integrate and patterned NST features into N/MEMS devices [6]. In this technique, patterned Ti films are reacted with aqueous hydrogen peroxide (aq. H2O2) to form integrated NST features. Although there are prior reports on the reaction between Ti and aq. H2O2, there is little prior work that investigated the effects of Ti microstructure on the reaction kinetics [7-9]. Here, we present initial results of our efforts to investigate the effect of parent Ti microstructure such as average grain size and thickness on the reaction kinetics between Ti films and aq. H2O2. One simple technique to monitor the kinetics of reaction involving metal films is to measure the change of electrical resistance with time [10]. Using this method, the oxidation kinetics of Ti in the presence of oxygen gas was recently reported [11]. In this
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study, we use a similar technique to monitor the oxidation kinetics of Ti films reacting with an aqueous H2O2 solution. EXPERIMENTAL DETAILS A schematic of the set up used for electro-oxidation investigations is shown in Figure 1. Patterns of Ti lines were deposited on gl
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