This Nanotech West Lab Research News article was contributed by the group of Prof. Wu Lu, Professor of Electrical and Computer Engineering, of The Ohio State University

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Read more: Electron Transport of Schottky Barrier ZnO Nanowire Field Effect Transistors
ZnO nanowires (NWs) have attracted great attention as an important material for electronic and optoelectronic device applications due to its wide band gap and high exciton binding energy. It is a native n-type material and the electronic conduction in nominally un-doped ZnO materials is a result from native defects such as unintentionally-doped impurities and structural imperfections. However, owing to its complexity, the electrical transport in ZnO devices is often thought to be controversial. It can be even more intangible in the case of quasi-one-dimensional ZnO NWs based devices. For example, Does the electron transport of ZnO NW field effect transistors (FETs) follow the same mechanism of ZnO thin film FETs? Do they follow the same electron transport mechanism at different temperatures? What is the carrier mobility and trap density in ZnO NW FETs? In addition, electrical contacts on such ZnO NWs are also difficult to characterize due to the lacking of an established model. Because of the high surface to volume ratio of NWs, the hypothesis that metal contacts on ZnO NWs exhibit the same or similar characteristics with those contacts on ZnO thin films is not necessarily true because the Fermi-level can be pinned by surface states. Therefore it is fundamentally important to establish a model and revisit this issue.

This Nanotech West Lab Research News article was contributed by Dr. Santino Carnevale in the research group of Prof. Steven Ringel, Neal A. Smith Chair Professor Electrical and Computer Engineering, of The Ohio State University.

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Read more: Electron Channeling Contrast Imaging for Rapid Extended Defect Characterization
When researchers consider how to image extended defects (e.g. dislocations, stacking faults) in single crystal samples, in all likelihood the first technique they consider is transmission electron microscopy (TEM). After all, TEM has been the most widely used method for characterizing extended defects for decades, and can provide a wealth of information regarding a sample's microstructure. Unfortunately, TEM imaging requires that samples are electron transparent, which usually means the material needs to be thinned with some combination of polishing and/or focused ion beam milling. This sample preparation can be quite time consuming and possibly lead to a bottleneck in research progress when characterizing a large number of samples.

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Read more: HfO2 Speckle Patterns for Measuring Local Deformation in Nickel-base Superalloys
The next generation of advanced power plants in the United States will place high demands on the materials used to build them: steam turbine blades will continuously experience temperatures up to 750 ºC and stresses of 150 MPa for the lifetime of the plant. Designing materials to withstand these extreme conditions over a period of years requires a nuanced understanding of how candidate materials will respond across multiple length scales, from individual atoms to the full turbine blade component.

[The following research report was contributed by the research group of Prof. Wendy Panero of the Ohio State School of Earth Sciences, particularly by graduate student Jeff Pigott]

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Read more: Microfabricated “Hotplates” for Understanding the Materials Science of the Earth’s Core

The dynamics of the planet Earth, as controlled by the rock composition at depth and the thermal variations within the interior, drive plate tectonics, generate the planet’s magnetic field, and produce intraplate magmatism such as that of Hawaii. The determination of the state and evolution of the Earth’s deep interior requires multiple remote measurements, including the measurement of the three-dimensional sound velocity field as measured by seismic wave speeds arising from earthquakes around the globe. The field of high-pressure mineral physics serves to tie the wave speeds to the physical properties of rocks under the relevant pressures and temperatures of the Earth’s interior, in which simultaneous mineral phase, pressure, temperature, and density measurements constrain wave speeds as a function of composition. This requires measurement at the pressures and temperatures relevant to the Earth’s deep interior (to 360 GPa and 7000 K).

[This Nanotech West Lab Research News article was contributed by the group of Prof. Ron Reano, Associate Professor of Electrical and Computer Engineering, and ElectroScience Laboratory, of The Ohio State University]

Silicon photonics is a promising approach for chip-scale integrated optics. A single-mode silicon strip waveguide designed for operation in the infrared, for example, has a typical submicron cross-section of 450 nm x 250 nm. Highly confined optical modes allow for high density integration and waveguide bends with micrometer scale radii of curvature. The high confinement, however, also produces major challenges when attempting to efficiently couple light between silicon strip waveguides and optical fibers.  Mode conversion from a single-mode fiber, with mode field diameter equal to 10 micrometers, results in a coupling loss that is greater than 20 dB. Current methods designed to achieve efficient fiber-to-chip coupling generally involve edge coupling using inverse width tapered waveguides or surface coupling using grating couplers. Inverse width tapers enable low loss and broadband edge coupling but require dicing or cleaving the chip.  Alternatively, grating couplers enable light coupling via the surface of the chip without the need for cleaving.  They require, however, a tradeoff between bandwidth and efficiency.