Nanorods Produced on the Surface of Thin Films of TiOx by Surface-Imprinting
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Nanorods Produced on the Surface of Thin Films of TiOx by Surface-Imprinting
M. Joseph Roberts and Scott K. Johnson Polymer Science and Engineering Branch, Code 4T4220D, NAVAIR, NAWCWD, China Lake, CA 93555, USA ABSTRACT Worldwide, there is great interest in new processes for production of nanoscale features in materials surfaces. Our recent work explores imprinting of nanosized objects into thin films. In this paper, we present results from surface imprinting of TiOx sol-gel films with anodized alumina. Scanning Probe Microscopy provides evidence for the quality of the imprinting process. INTRODUCTION In this report, we begin by describing some of the processes for production of nanoscale features. New methods include nano-imprinting lithography (NIL), molecular imprinting (MI), surface imprinting (SI), and templating. There are both important distinctions between these methods yet they have been combined or altered as needed or dictated by the material properties and design requirements. Nanoimprinting lithography (NIL) is an especially interesting approach for nanoscale pattern generation since it is in principle scalable, parallel, and cost-effective [1]. NIL has been used most widely for creating features with a resolution of 100 nm. In NIL, a resist relief pattern is generated via compression molding (or embossing) of a deformable polymer by a hard inorganic stamp, rather than by modifying the resist chemical structure with radiation or selfassembly. This pattern is typically transferred to the underlying substrate by anisotropic reactive ion etching (RIE), followed by material deposition and liftoff of the remaining polymer. In general, polymers used for NIL must be heated above the glass transition temperature (ca. 200 ºC) to enable flow during the imprinting step. Typically, in the molecular imprinting (MI) processes, a cross-linking polymerization of a mixture of a molecule of interest, a monomer and porogen is performed, followed by extraction of the molecule of interest, which leaves a porous polymer with imprints of the molecule of interest over its surface. There are many variations on the process of MI and the interested reader is referred to other papers in this volume for more on this subject. Recent studies have reported room-temperature nanometer-scale imprinting of polymers on silicon substrates. Since imprint lithography is not based on modification of resist chemical structure by radiation, its resolution is immune to many factors that limit the resolution of conventional lithography, such as wave diffraction, scattering and interference in a resist, backscattering from a substrate, and the chemistry of resist and developer [2,3]. Liquid embossing with an elastomeric stamp is another method that facilitates direct patterning of electrical, biological, chemical, and mechanical materials [4]. Embossing with a patterned elastomeric stamp patterns a thin liquid film. The patterned liquid is then cured to form a functional layer. This technique is limited in that it requires a elastomeric s
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