Selected Publications
Nitesh Madaan, Aaron Terry, Robert C. Davis, and Matthew R. Linford (et al.)
Instrumentation and Techniques Symposia
Guilin Jiang, Felipe Rivera, Supriya S. Kanyal, Robert C. Davis, Richard Vanfleet, Barry M. Lunt, and Natthew R. Linford
The plastic substrates, reflective layers, dyes, and adhesives of four archival-grade DVDs and one standard-grade recordable DVD were analyzed to determine their chemical compositions and/or physical dimensions. Chemical analyses by ATR-FTIR, ToF-SIMS, XPS and EDX/STEM show that all these DVDs use very similar polycarbonate plastic substrates and acrylate-based adhesives, but different reflective layers and dye write layers. In addition, physical measurements by AFM show differences in the DVD groove depth, width, and other dimensions. These chemical and physical analyses may help explain variations in DVD lifetimes and facilitate development of the next generation of archival-grade DVDs.
Todd D. Wickard, Emily Nelsen, Nitesh Madaan, Robert C. Davis, and Matthew R. Linford (et al.)
We report the first attachment of polymers with pendant vinyl groups to hydrogen-terminated silicon(111) (Si(111)-H); 1,2-polybutadiene (M(w) = 3200-3500 g/mol) was attached to Si(111)-H under mild conditions at room temperature with visible light. We also report the partial functionalization, in solution, of 1,2-polybutadiene with various thiols using thiol-ene chemistry and the Subsequent attachments of these compounds to Si(111)-H. The partially functionalized or unfunctionalized polybutadienes allow further functionalization at the surface through their unreacted carbon-carbon double bonds. We present this as a useful strategy for Silicon Surface modification, Surfaces were characterized with contact angle goniometry, spectroscopic ellipsometry X-ray photoelectron spectroscopy (XIS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM).
David N. Hutchison, Nicholas B. Morrill, Quentin Aten, Brendan W. Turner, Brian D. Jensen, Larry L. Howell, Richard R. Vanfleet, and Robert C. Davis
A class of carbon-nanotube (CNT) composite materials was developed to take advantage of the precise high-aspect-ratio shape of patterned vertically grown nanotube forests. These patterned forests were rendered mechanically robust by chemical vapor infiltration and released by etching an underlying sacrificial layer. We fabricated a diverse variety of functional MEMS devices, including cantilevers, bistable mechanisms, and thermomechanical actuators, using this technique. A wide range of chemical-vapor-depositable materials could be used as fillers; here, we specifically explored infiltration by silicon and silicon nitride. The CNT framework technique may enable high-aspect-ratio MEMS fabrication from a variety of materials with desired properties such as high-temperature stability or robustness. The elastic modulus of the silicon-nanotube and silicon nitride-nanotube composites is dominated by the filler material, but they remain electrically conductive, even when the filler (over 99% of the composite's mass) is insulating. [2009-0197]
D. N. Hutchison, Q. Aten, B. Turner, N. Morrill, B. D. Jensen, R. C. Davis, and R. R. Vanfleet
We recently developed a fabrication process for carbon nanotube templated MEMS. The fabrication process involves growing a three dimensional pattern from carbon nanotube forests and filling that forest by chemical vapor infiltration to make a solid structure. This templating process allows us to fabricate extremely high aspect ratio microscale structures from a wide variety of materials. The nanotube structures can be hundreds of microns tall with lateral pattern dimensions down to a few microns. The chemical vapor infiltration has been shown with silicon and silicon nitride but could be extended to many other materials. In this paper, we investigate the microstructure of the filling material and extend the process to the fabrication of comb actuators.
Vanadium dioxide (VO2) single crystals undergo a structural first-order metal to insulator phase transition at approximately 68°C. This phase transition exhibits a resistivity change of up to 5 orders of magnitude in bulk specimens. We observe a 2-3 order of magnitude change in thin films of VO2. Individual particles with sizes ranging from 50 to 250 nm were studied by means of Transmission Electron Microscopy (TEM). The structural transition for individual particles was observed as a function of temperature. Furthermore, the interface between grains was also studied. We present our current progress in understanding this phase transition for polycrystalline thin films of VO2 from the view of individual particles.