Highlights
Dec 19, 2008
Northwestern University
Atomic Force Photovoltaic Microscopy
B. J. Leever, M. F. Durstock, M. D. Irwin, A. W. Hains, T. J. Marks, L. S. C. Pingree, and M. C. Hersam Northwestern University Materials Research Science & Engineering Center DMR-0520513
Organic photovoltaic devices (OPVs) hold promise for a variety of applications requiring alternative energy generation. Through a collaboration betweenÂ’ Northwestern University MRSEC IRG 4 and Wright Patterson Air Force Base, a new strategy for characterizing the electrical and optical performance of operating OPVs has recently been developed. Atomic force photovoltaic microscopy allows the photocurrent response in OPVs and other optoelectronically-active materials and devices to be spatially mapped down to the nanometer length scale.
Dec 19, 2008
Northwestern University
The Art of Science and the Science of Art
Katherine T. Faber Northwestern University Materials Research Science & Engineering Center, DMR-0520513
A partnership between the NU-MRSEC and the Art Institute of Chicago provides fertile ground for curriculum development. Lisa Backus, a high school chemistry teacher and participant in the Center's 2006Â’ Research Experience for Teachers (RET) program was inspired by her summer research project working on conservation science problems of Ancient Chinese jades and Winslow Homer watercolors. The result is an art-based high school chemistry module that introduces students to the properties of light, the atom, and organic compound pigments.
Oct 27, 2008
Princeton University
Quantum Memory Preserves Coherence for over 1 Second in Silicon
John J. L. Morton, Alexei M. Tyryshkin, Richard M. Brown, Shyam Shankar, Brendon W. Lovett, Arzhang Ardavan, Thomas Schenkel, Eugene E. Haller, Joel W. Ager and Stephen A. Lyon
One of the key hurdles to building a large quantum computer is maintaining the coherence of the many individual two-level quantum mechanical systems, or qubits. Atoms and ions in a vacuum or nuclear spins in solids and liquids can have long coherence, but it is not yet known how well those systems can be scaled to make a large computer. Ideally one could use the spin of an electron in a semiconductor as a qubit, since modern semiconductor technology is based upon moving and controlling electrons in silicon.
Aug 29, 2008
Princeton University
Phase Transition of Dirac Electrons in Bismuth
Lu Li, Joe Checkelsky, Yew San Hor, Ctirad Uher (Michigan), Arthur Hebard (Florida), Bob Cava, and Phuan Ong
The energy E of a bowling ball increases as the square of its velocity (or momentum p). This is also generally true for electrons in solids, which are accurately described by the Schràƒ’¶dinger equation (Fig. 1a). However, in a small set of materials - e.g. bismuth, antimony and graphene - E increases linearly with p (Fig. 1b). To describe this unusual behavior, we resort to the Dirac equation, which has been very successful in describing neutrinos and high-energy electrons.
Aug 29, 2008
Princeton University
Nanoscale Imaging Shows Link between Attractive and Repulsive Forces in Copper-Oxide Superconductors
Abhay Pasupathy, Aakash Pushp, Kenjiro Gomes, Colin Parker, Jinsheng Wen, Zhijun Xu, Genda Gu, Shimpei Ono, Yoichi Ando, and Ali Yazdani
In a normal material, electrons repel each other due to their charge. In the copper-oxide superconductors, however, an attractive force develops between electrons that pairs them up at temperatures up to 140 degrees above absolute zero. Understanding the reason for this pairing has remained an elusive goal in condensed matter physics research over the past two decades.
Aug 5, 2008
California Institute of Technology
Low Density Ti-based Bulk Metallic Glasses as a Matrix For High Performance Metallic Glass Composite
W.L. Johnson
In a recent publication in Nature, we reported bulk metallic glass (BMG) matrix
composites exhibiting >10% tensile ductility and Fracture Toughness comparable to or
exceeding the toughest metals known [1]. These high performance composites
demonstrate the potential of metallic glass as revolutionary structural metals. The BMG matrix
composites contain elastically soft dendrites comprised of Ti-Zr-Nb embedded in
a glassy matrix. Toughening and ductility are achieved by a mechanism similar to the
Aug 5, 2008
California Institute of Technology
How to Avoid Parasitic Cracks During Layer Transfer
H.A. Atwater, K. Bhattacharya, G. Ravichandran
Producing high quality thin films of controlled thickness is a critical step for the development of ferroelectric nanophotonic devices. Developed recently, the process referred to as layer transfer has been shown to be very promising: ions are implanted in a plan parallel to the interface of a bilayer system that is then heated. The high temperature induces nucleation and propagation of cracks in the weakened plan of the specimen, resulting after coalescence in a full splitting of the upper part of the original sample (Fig. (a)).
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