Selected Publications

BYU Authors: D. N. Hutchison, Q. Aten, B. Turner, N. Morrill, B. D. Jensen, R. C. Davis, and R. R. Vanfleet, published in Solid-State Sensors, Actuators and Microsystems: Transducers 2009 (June 2009, Denver, CO).
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.
BYU Authors: Felipe Rivera, Robert C. Davis, and Richard Vanfleet, published in MRS Proc.
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.
BYU Authors: Robert C. Davis, published in Phys. Rev. Lett.
To demonstrate the potential for microelectromechanical systems, nanotube beams composed from self-assembled closely packed and aligned single-walled carbon nanotubes were fabricated and their mechanical properties were measured. We found that the nanotube beams behave as a cohesive, rigid, and elastic body with a sound velocity of 10 100 m/s.
BYU Authors: Feng Zhang, Robert C. Davis, and Matthew R. Linford, published in Langmuir
Here we present a straightforward patterning technique for silicon: subsurface oxidation for micropatterning silicon (SOMS). In this method, a stencil mask is placed above a silicon surface. Radio-frequency plasma oxidation of the substrate creates a pattern of thicker oxide in the exposed regions. Etching with HF or KOH produces very shallow or much higher aspect ratio features on silicon, respectively, where patterning is confirmed by atomic force microscopy, scanning electron microscopy, and optical microscopy. The oxidation process itself is studied under a variety of reaction conditions, including higher and lower oxygen pressures (2 and 0.5 Torr), a variety of powers (50-400 W), different times and as a function of reagent purity (99.5 or 99.994% oxygen). SOMS can be easily executed in any normal chemistry laboratory with a plasma generator. Because of its simplicity, it may have industrial viability.
BYU Authors: Hiram Conley and Robert Davis, published in Chem. Eur. J.
The self-assembly and characterization of a novel supramolecular amphiphile built from a new 60 degrees amphiphilic precursor that incorporates hydrophilic platinum(II) metals and hydrophobic dioctadecyloxy chains is reported. The amphiphilic macrocycle and its precursor compound have been characterized by multinuclear NMR spectroscopy, ESI-MS, and other standard techniques. The coacervate morphology of the amphiphile at the liquid-liquid interface has been studied by using confocal optical microscopy and in situ Raman spectroscopy. The self-assembly of the amphiphilic macrocycle at the air-water interface has been investigated through Langmuirtrough techniques. The study indicates the possible formation of surface micelle-like aggregates. The disparity between the experimental molecular areas and those derived from molecular models support the idea of aggregation. AFM images of the surface aggregates show the formation of a flat topology with arbitrary ridgelike patterns. Reasonable molecular-packing arrangements are proposed to explain the molecular organization within the observed structures.
BYU Authors: Hiram Conley and Robert Davis, published in Langmuir
Organoplatinum(II) gemini amphiphiles with two different chain lengths are synthesized and characterized. Self-assembly at the air-water interface is investigated as a function of chain length and reduction in surface area by using Langmuir-trough techniques. The Langmuir-trough experiments lead to a conjecture that surface aggregates may be the adsorbing units. Atomic force microscopy on the transferred Langmuir- Schaefer films reveals spontaneous formation of wormlike micellar aggregates. A shear-induced transition and alignment are proposed for the observed effects.