Computers that could switch on instantly without the time-consuming process of “booting” an operating system is just one of the possibilities, according to a new paper by a team of researchers spanning four universities, two federal laboratories and three corporate labs.*
Almost exactly two years ago, a team led by Joseph Woicik of NIST and several other federal, academic and industrial laboratories combined precision X-ray spectroscopy data from the NIST beamlines at the National Synchrotron Light Source with theoretical calculations to demonstrate that by carefully layering a thin film of strontium titanate onto a pure silicon crystal, they could distort the titanium compound into something it normally wasn’t—a so-called “ferroelectric” compound that might serve as a fast, efficient medium for data storage.** The new paper adds a key experimental and technological demonstration—the ability to write, read, store and erase patterned bits of data in the strontium titanate film.
In contrast to a traditional data storage material, which records data as a pattern of magnetic regions pointing in different directions, a ferroelectric can do the same with tiny regions of polarized electric charges. Ferroelectric memories are used, for example, in “smart cards” for subway systems. Ferroelectric structures that could be built directly onto silicon crystals, the most common materials base for consumer electronics, have been sought for years for a variety of applications, including nonvolatile memory (data that is not lost when power is turned off) and temperature or pressure sensors integrated into silicon-based microelectronics. One of the potentially biggest prizes would be ferroelectric transistors that could retain their logic state (“on” or “off”) without power, which could enable computers that switch on instantly without needing a boot stage.
The breakthrough originated with researcher Hao Li of Motorola, Inc., who succeeded in depositing the metal oxide directly onto silicon with no intervening layer of silicon oxide producing “coherency” between the two crystal structures—the unique matching up perfectly of one atom to the next across the metal-oxide/Si interface. This is a difficult trick both because silicon is highly reactive to oxidation and because the crystal spacing of the two materials does not normally match. Guided by precision X-ray diffraction data from NIST, Li developed a finely controlled method of depositing the strontium titanate in stages, gradually building up layers that were only a few molecules thick. The result, X-ray data showed, was that the silicon atoms literally squeezed the cubic strontium-titanate crystal to make it fit, distorting it into an oblong shape. That distortion creates a structural instability in the film that makes the compound a ferroelectric.
While theoretical calculations and spectroscopic data demonstrated that the distorted crystal behaved like a ferroelectric, proof of the ferroelectric functionality waited on the new work led by Cornell University professor Darrell Schlom, whose team used a technique called piezoresponse force microscopy to write, read and erase polarized domains in the strontium titanate film.
Researchers from Cornell, the University of Pittsburgh, NIST, Pennsylvania State University, Northwestern University, Motorola, the Energy Department’s Ames Laboratory, Intel Corporation, and Tricorn Tech contributed to the latest paper. X-ray diffraction data were taken at the Advanced Photon Source, Argonne National Laboratory. The research was funded in part by the Office of Naval Research and the National Science Foundation.
* M.P. Warusawithana, C. Cen, C.R. Sleasman, J.C. Woicik, Y. Li, L.F. Kourkoutis, J.A. Klug, H. Li, P. Ryan, L.-P. Wang, M. Bedzyk, D.A. Muller, L.-Q. Chen, J. Levy and D.G. Schlom. A ferroelectric oxide made directly on silicon. Science V 324 17 April 17, 2009. DOI: 10.1126/science.1169678.
** J.C. Woicik, E.L. Shirley, C.S. Hellberg, K.E. Andersen, S. Sambasivan, D.A. Fischer, B.D. Chapman, E.A. Stern, P. Ryan, D.L. Ederer and H. Li. Ferroelectric distortion in SrTiO3 thin films on Si (001) by x-ray absorption fine structure spectroscopy: Experiment and first-principles calculations. Physical Review B 75, Rapid Communications, 140103 April 24, 2007. DOI: 10.1103/PhysRevB.75.140103.
Michael Baum | Newswise Science News
An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Treated carbon pulls radioactive elements from water
20.01.2017 | Rice University
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences