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Back by popular demand! [View additional news and highlights on the MRS Web site] The second day of the meeting saw most symposia begin sessions which were held at the Moscone West convention center. Major events of the day included symposium X talks at noon on sub-45 nm CMOS technology and the applications of materials science for the repair of humans, the first poster sessions of the meeting, presentations by the graduate student award finalists, the opening of the equipment exhibit and seminars by funding agencies.
“I
can’t think of a better use of materials than to
repair human beings.”
Symposium X - Frontiers of Materials Research "Materials
are key to continuous progress in CMOS technology." Sub-45nm
CMOS: A Grand Old Lady with New Clothes “Wouldn’t
you like to die with your own teeth?” Materials
Science for the Repair of Humans Stupp then described the use of self assembly to form fibers which form the basis for the matrices. He showed an example of self assembled nanofibers using bioactive peptide amphiphilic molecules which have hydrophobic "tails". The self-assembled fibers interconnect and form networks. A large variety of molecules can be made for this purpose and living cells can be added for the purposes of regeneration which are encapsulated within the network. Stupp gave an example of work on regeneration of the spinal cord. The nanofibers matrix was loaded with neural cells which within 24 hours become neurons. A liquid can thus be injected into the spinal chord after an injury for complete repair. Stupp gave various other examples. While the promise of true regenerative medicine is still many years away, he reiterated that the use of materials for this purpose has elevated materials science to a higher plane because of the implications for human body repair.
Scientific
and Technical Talks
In symposium D on High-k Insulators and Ferroelectrics, Orlando Auciello (Argonne National Lab.) presented some interesting work on the development of a novel TiAlOx alloy as an alternative gate oxide material for CMOS devices. 3-20 nm TiAl films were grown on n-Si and subjected to in situ oxidation using molecular and atomic oxygen. The TiAlOx thus formed was amorphous and the layer formed using atomic oxygen annealing showed a leakage current 150 times lower than the one using molecular oxygen. TiAlOx layers with equivalent oxygen thickness less than 1 nm were achieved on Si using room temperature oxidation with atomic oxygen. With bandgaps of up to 4 eV, Auciello stressed that amorphous TiAlOx is a candidate for the next generation of high-k dielectrics. In back-to-back papers on Tuesday morning, first, in paper W.14/O1.4 and then in paper U1.5, Harvard Professor George M. Whitesides addressed new approaches to nanofabrication. In his first talk, Whitesides suggested that a planar microfabrication approach is more practical than the “beads-in-a-string” concept observed in nature and typically used in biomimetic approaches to self-assembly. As an example, a crimped sheet could be stretched flat to facilitate the printing of a circuit, and then released, thereby forming a three-dimensional circuit. In another example, cartographical techniques were employed to shape virtually flat pieces onto which circuits were printed and that could be later be assembled into spherical circuits. Whitesides also showed how, using common two-dimensional substrates, one-, two-, and three-dimensional structures could be constructed using volume-constrained self-assembly. In his second talk, Whitesides reviewed several unconventional approaches to nanofabrication advanced in his laboratory. Electron-beam writing was shown to form topographically patterned films with an ultimate resolution that is about an order of magnitude better than currently achieved by atomic force microspcopy. Examples of electric microcontact printing, edge lithography, and templated synthesis were also shown. Are flexible displays ready for "prime time"? Not quite, said Kimberly Allen of iSuppli/Standford Resources, who gave the first talk in Symposium I. However, progress on all fronts looks promising, she said, with continued development likely able to handle foreseeable obstacles. Some challenges remain across the board, from finding a substrate that repeatedly flexes yet retains dimensional stability through temperature changes, to finding a way to get a pattern on to a flexible substrate. While applications, such as eletrophoretic dynamic signage, are emerging and are likely to grow through this decade, Allen says that there is no "killer app," an application that will drive this technology to large-scale commercialization because of its unique need for this solution. While early images touted the idea of roll-to-roll processing, batch processing seems more suited to many likely applications, she said.
A big issue in small-molecule light-emitting diodes, particularly flexible ones, is the issue of how to block moisture. With an image of a crumbling wall of bricks trying to hold out a sea of water, P.E. Burrows (Pacific Northwest National Laboratory) described just how permeable to water the organic films are, in his symposium I talk. He described a multilayer system that works, although at first glance its success seems unlikely. The alternating layers of polymer and ceramic serve to decouple defects from previous layers (with the planarizing polymer) and to block the flow of moisture (due to the thin aluminum oxide ceramic layer). While equilibrium calculations indicate the moisture cannot be kept out with such a barrier, the reality is that the films do work. This is due, he said, due to the more realistic nonequillibrium kinetics, which indicates a lag time that increases with more layers, buying time on the order of years before permeation causes destruction. Burrows also presented a new technique for rapid, continuous production of OLEDs, using several external syringe pumps which feed a liquid solution into a box, where the material is vaporized and the right mix and temperature is maintained and fed to produce the OLEDs films. Funding
Agencies Seminars Hydrogen
Research: Department of Energy (DOE) Seminar
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