MVC 1 Awards Gallery
BEST OF SHOW
“PARYLENE COATED MEMS BASED
PIEZOELECTRIC ULTRASOUND TRANSDUCER ARRAY“
Flavio Griggio, Graduate Student, Materials Science and Engineering
Scientific Process: A linear array of xylophone bar type transducer was fabricated using PbZr0.52Ti0.48O3 (PZT) as the active piezoelectric layer. Similar fabricated transducers have 63MHz center frequency and 30% of 6dB bandwidth. The resulting PZT linear array is compatible with low‐voltage CMOS (<3.3 V) and we havedesigned and fabricated a fully integrated CMOS transceiver chip to interface with the transducer array.
SCIENTIFIC CATEGORY
FIRST PLACE
“SURFACE TOPOGRAPHY AFTER 7×1012 AU3 IMPACTS PER CM2“
Barbara Garrison, Faculty, Chemistry and MRI, with Michael F. Russo and Zbigniew Postawa, Materials Science and Engineering
Scientific Process: Energetic ion beams are used for a diverse set of applications including ion beam modification of surfaces and depth profiling through atomic and molecular substrates. Computer simulations of repetitive bombardment of surfaces have previously been impossible, thus a microscopic picture of topology development has not been available. We have developed a novel divide and conquer protocol to model repetitive bombardment of energetic particles such as 20 keV Au3. The total sample is 53 nm on a side with 4.5 million silver atoms. By using subsystems of ~200,000 Ag atoms for each Au3 impact and calculating several subsystems simultaneously, we are able to provide efficiently the first atomistic view of repetitive cluster bombardment. In the figure shown, the net yield is only approximately two atomic layers of material (~0.5 nm) yet topology develops that ranges from 4.5 nm above the original surface to 8 nm below the original surface.
SECOND PLACE
“A TRANSMISSION ELECTRON MICROGRAPH OF A LAB6-ZRB2 FIBER-TYPE EUTECTIC CERAMIC COMPOSITE SHOWS PLASTIC DEFORMATION“
Ryan White, Graduate Student, Materials Science and Engineering
Scientific Process: LaB6-ZrB2 composites were grown using a common floating-zone method and have a fiber-type eutectic microstructure. In this transmission electron micrograph, the growth direction of the composite is oriented perpendicular to the plane of the image, providing a cross section of the ZrB2 fibers and LaB6 matrix. This specific sample was extracted from directly beneath a Vickers hardness indentation with the focused ion beam and thinned to electron transparency in-situ. This site specific sample preparation allowed for visualization of plastic deformation which would otherwise be disturbed by conventional TEM sample preparation methods.
THIRD PLACE
“A FOREST OF SILICON NANOWIRES FORMED BY AU DIFFUSION DOWN THE SIDES OF THE NANOWIRES NUCLEATING ADDITIONAL NANOWIRE GROWTH“
Sarah Eichfeld, Graduate Student, Materials Science and Engineering
Scientific Process: The sample consists of p-type silicon nanowires (SiNWs) grown using SiCl4, which allows for oriented SiNW growth on a Si (111) substrate. The nanowire “trunks” are 120 +/- 50 nm in diameter and 10µm long. The goal was to then grow a radial n-type coating on the SiNW for photovoltaic applications. In this experiment the Au catalyst used to grow the initial nanowires was not removed and upon reheating for the radial Si deposition resulted in a nanowire forest. This was due to Au diffusion down the sides of the SiNW that nucleated small n-type SiNW “branches” on the initial nanowire trunk. The diameter of the nanobranches varies from 25-50nm. This experiment revealed the extent of Au diffusion occurring during cooldown of SiNW growth and that removal of the Au tip is crucial for radial Si deposition. A green color was added to the FESEM image to enhance the image.
VISUAL CATEGORY
FIRST PLACE
“DENDRITIC GROWTH OF BISMUTH MODIFIED PbTiO3 PRODUCES
THESE INTERLOCKING CRYSTAL PLATES “
Stephen F. Poterala, Graduate Student, Materials Science and Engineering
Scientific Process: This dendritic lead titanate (PbTiO³) was formed by reaction of lead bismuth titanate (PbBi4Ti4O15) with PbO in a KCl flux at 1100°C. During this reaction a PbTiO³-PbO liquid forms and phase separates from the chloride flux. Intermediate PbTiO³-PbBi4Ti4O15 phases grow very rapidly in this oxide liquid, leading to large dendritic crystal clusters. Eventually the reaction completes, and the grown dendrites are fully converted to the perovskite phase.
SECOND PLACE
“A 176 nm THICK NiAL INTERMETALLIC THIN FILM AFTER ETCHING
IN HYDROFLUORIC ACID FOR 10 MINUTES“
Jane Howell, Graduate Student, Materials Science and Engineering
Scientific Process: Intermetallic thin films show great promise in the area of microelectromechanical systems (MEMS). NiAl in particular is being studied for these applications, and simple devices such as thermal actuators and resonators have been fabricated and tested. The film in the image was an early attempt at creating free-standing films, but the tensile stresses in the film combined with the hydrofluoric acid etch generated extensive cracking in the films. Spiral crack patterns were often observed, and areas of bare substrate can be seen where film de-lamination has occurred. Changes in the substrate, deposition conditions, and etchant have led to crack free films and devices.
THIRD PLACE
“25µm-LONG OCTOPUS ARMS ARE STRETCHED OUT FROM
THE SILICON PLANAR BODY TO CAPTURE PREY“
Heayoung Yoon, Post Doc & Yuwen Yu. Graduate Student, Electrical Engineering
Scientific Process: This is a Field Emission-Scanning Electron Microscopy (FE-SEM) image of etched silicon pillar arrays. Following optical lithography to pattern the 1 µm-diameter circles, the planar silicon wafer was placed in Deep Reactive Ion Etching (DRIE) system and etched for 10 minutes. The scalloping features on the side-wall of 25 µm-high pillars come from the BOSCH process, which alternates repeatedly between two modes (deposition and etching) to achieve vertical structure. The high-aspect-ratio pillars seem to be collapsed during the wet chemical cleaning/dry process due to the strong capillary force.
