Read full article at PennState website

Credit: Sava Denev, Penn State

A “non-magnetic lattice,” shown in Figure A, can have the same symmetry as a magnetic lattice, shown in Figure B. Both lattices, in this case, are described as having the point group symmetry that the scientists call 4′mm’.

Figure A (”non-magnetic” material): The “non-magnetic” crystal structure of strontium titanate, SrTiO₃, is composed of strontium (blue balls), titanium (red balls), and oxygen (yellow balls). The grey motifs are oxygen octahedra structures that twist counter to the neighboring octahedra, as shown by the green arrows.

A remarkably simple experiment devised by scientists yields important information about the mechanical properties of thin films–nanoscopically thin layers of material that are deposited onto a metal, ceramic or semiconductor base.

The research results, funded by the National Science Foundation and performed at the University of Massachusetts at Amherst Materials Research Science and Engineering Center, appears in the August 3, 2007, issue of Science.

The findings impact a broad range of scientific disciplines and applications, from cosmetics to coatings, to micro- and nanoelectronics. Understanding the mechanical properties of thin films is essential to their performance and optimization.

Until now, determining the mechanical properties of these thin films was either an expensive and time-consuming endeavor, requiring powerful microscopes to view the films, or scientists examined composite structures and made uncertain assumptions. This new research will give scientists a simple way to access the material properties of most thin films.

“As we delve more into the nanotechnology, it becomes increasingly important to know if the material properties of ultrathin films differ from their properties in the bulk,” said Thomas Russell, a program director in the Polymer Science and Engineering Department at the University of Massachusetts in Amherst. “Everyday we see examples where a material’s dimensions can change its properties. Aluminum foil is flexible, whereas a bar of aluminum is not. But what happens when a film’s thickness approaches molecular dimensions? These experiments give us a simple, inexpensive way to measure mechanical properties of films that are only tens of nanometers thick.”

Russell and his colleagues use a low-power optical microscope to observe what happens when they place a tiny drop of water on thin film as it floats in a Petri dish of water. The “capillary tension” of the drop of water produces a starburst of wrinkles in the film. The number and length of the wrinkles are determined by the elasticity and thickness of the film.

In some of the materials studied, the wrinkles in the ultrathin polymer films vanished with time, unlike the skin of a dried fruit or the crumpled hood of your car after an accident. This vanishing provides insight into the relaxation process of an ultrathin film by yielding information on the way polymer chains move in the highly confined geometry.

-NSF-

Media Contacts

Diane E. Banegas, NSF (703) 292-8070 dbanegas@nsf.gov

The purpose of this study was to:

1. Assess the performance and impact of the National Science Foundation’s Materials Research Science and Engineering Center (MRSEC) program;

2. On the basis of current trends and needs in materials and condensed matter research, recommend future directions and roles for the program.

Download NRC Report (1M)

Committee and Staff Members

Committee Membership

Matthew Tirrell, Chair, University of California at Santa Barbara
Kristi S. Anseth, University of Colorado at Boulder
Meigan Aronson, University of Michigan
David M. Ceperley, University of Illinois at Urbana-Champaign
Paul M. Chaikin, New York University
Ronald C. Davidson, Princeton University
Duane Dimos, Sandia National Laboratories
Francis J. DiSalvo, Cornell University
Edith Flanigen, UOP
Thomas F. Kuech, University of Wisconsin at Madison
Bruce Margon, Space Telescope Science Institute
Andrew Millis, Columbia University
Venkatesh Narayanamurti, Harvard University
Ralph Nuzzo, University of Illinois at Urbana-Champaign
Douglas D. Osheroff, Stanford University
Stuart Parkin, IBM Almaden Research Center
Diandra L. Leslie-Pelecky, University of Nebraska
Julia M. Phillips, Sandia National Laboratories
Lyle Schwartz, retired, Air Force Office of Science Research
Eli Yablonovitch, University of California at Los Angeles

Consultants

Neil E. Paton, LiquidMetal Technologies

NRC Staff

Donald C. Shapero, Director
Timothy I. Meyer, Program Officer
David B. Lang, Research Assistant

• University of Washington
• Yale University

Dr. W. Lance Haworth, Executive Officer of the National Science Foundation Division of Materials Research, gave an overview presentation of the MRSEC program using the Paul Gauguin painting (displayed in the Museum of Fine Arts, Boston) “Where Do We Come From? What Are We? Where Are We Going?” as a metaphor for the talk. He said the title was very appropriate for the celebration.

Next, Alan MacDiarmid (Univ. Penn.) who is one of the 2000 Nobel Laureates in Chemistry, talked about interdisciplinarity and its importance for scientific research, particularly for materials research. He said that interdisciplinarity is at the heart of the MRSEC program.

Following the talks, there was a poster session displaying the work and accomplishments of the various MRSECs and a reception.

The complete news article may be found at the MRS website, Fall 2004 Meeting, News & Highlights for Tuesday, November 30, NSF MRSEC - 10th Anniversary Celebration.
(more…)