Navigation Links
A deeper look at interfaces
Date:1/15/2014

"The interface is the device," Nobel laureate Herbert Kroemer famously observed, referring to the remarkable properties to be found at the junctures where layers of different materials meet. In today's burgeoning world of nanotechnology, the interfaces between layers of metal oxides are becoming increasingly prominent, with applications in such high-tech favorites as spintronics, high-temperature superconductors, ferroelectrics and multiferroics. Realizing the vast potential of these metal oxide interfaces, especially those buried in subsurface layers, will require detailed knowledge of their electronic structure. A new technique from an international team of researchers working at Berkeley Lab's Advanced Light Source (ALS) promises to deliver the goods.

In a study led by Charles Fadley, a physicist who holds joint appointments with Berkeley Lab's Materials Sciences Division and the University of California Davis, where he is a Distinguished Professor of Physics, the team combined two well-established techniques for studying electronic structure in crystalline materials into a new technique that is optimized for examining electronic properties at subsurface interfaces. They call this new technique SWARPES, for Standing Wave Angle-Resolved Photoemission Spectroscopy.

"SWARPES allows us for the first time to selectively study buried interfaces with either soft or hard x-rays," Fadley says. "The technique can be applied to any multilayer prototype device structure in spintronics, strongly correlated/high-TC superconductors, or semiconductor electronics. The only limitations are that the sample has to have a high degree of crystalline order, and has to be grown on a nanoscale multilayer mirror suitable for generating an x-ray standing wave."

As the name indicates, SWARPES combines the use of standing waves of x-rays with ARPES, the technique of choice for studying electronic structure. A standing wave is a vibrational pattern created when two waves of identical wavelength interfere with one another: one is the incident x-ray and the other is the x-ray reflected by a mirror. Interactions between standing waves and core-level electrons reveal much about the properties of each atomic species in a sample. ARPES from the outer valence levels is the long-standing spectroscopic workhorse for the study of electronic structure. X-rays striking a material surface or interface cause the photoemission of electrons at angles and kinetic energies that can be measured to obtain detailed electronic energy levels of the sample. While an extremely powerful tool, ARPES, a soft x-ray technique, is primarily limited to the study of near-surface atoms. It's harder x-ray cousin, HARPES, makes use of more energetic x-rays to effectively probe subsurface interfaces, but the addition of the standing wave capability provides a much desired depth selectivity.

"The standing wave can be moved up and down in a sample simply by rocking the angle of incidence around the Bragg angle of the mirror," says Alexander Gray, a former member of Fadley's UC Davis research group and affiliate with Berkeley Lab's Materials Sciences Division, who is now a postdoctoral associate at Stanford/SLAC. "Observing an interface between a ferromagnetic conductor (lanthanum strontium manganite) and an insulator (strontium titanate), which constitute a magnetic tunnel junction used in spintronic logic circuits, we've shown that changes in the electronic structure can be reliably measured, and that these changes are semi-quantitatively predicted by theory at several levels. Our results point to a much wider use of SWARPES in the future for studying the electronic properties of buried interfaces of many different kinds."


'/>"/>
Contact: Lynn Yarris
lcyarris@lbl.gov
510-486-5375
DOE/Lawrence Berkeley National Laboratory
Source:Eurekalert  

Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
A deeper look at interfaces
(Date:6/23/2017)... ... June 23, 2017 , ... Ken Hanson, a medical imaging research scientist at ... been selected as this year’s recipients of two top awards from SPIE, the ... with other honorees to accept their awards at a banquet in San Diego, California, ...
(Date:6/23/2017)... IN (PRWEB) , ... June 23, 2017 , ... ... voice for model aircraft flying hobbyists, and the University Aviation Association (UAA), the ... college students. The UAS4STEM Collegiate Challenge will encourage teamwork, competition, and success through ...
(Date:6/22/2017)... ... June 21, 2017 , ... RMC Pharmaceutical Solutions, Inc. ... Timothy Reinhardt to manage the new site. , Tim has 25 years of ... most recent role as the Director of Manufacturing and Supplier Quality Assessment. ...
(Date:6/22/2017)... ... 2017 , ... AESKU.GROUP, an innovation leader in autoimmune ... GmbH, thereby expanding its product portfolio to include allergy and food intolerance diagnostics. ... eczema or a food allergy. Allergies are escalating to epidemic proportions and becoming ...
Breaking Biology Technology:
(Date:3/24/2017)... Research and Markets has announced the addition of the ... Forecast to 2025" report to their offering. ... The Global Biometric Vehicle Access System ... over the next decade to reach approximately $1,580 million by 2025. ... forecasts for all the given segments on global as well as ...
(Date:3/23/2017)... , Mar. 23, 2017 Research and Markets ... Market Analysis & Trends - Industry Forecast to 2025" report ... ... at a CAGR of around 8.8% over the next decade to ... report analyzes the market estimates and forecasts for all the given ...
(Date:3/22/2017)... NEW YORK , March 21, 2017 /PRNewswire/ ... Customer Marketing Cloud used by retailers such as ... in its platform — Product Recommendations and Replenishment. Using ... to give more personalized product and replenishment recommendations ... purchases, but also on predictions of customer intent ...
Breaking Biology News(10 mins):