The National Institute of Standards and Technology (NIST) has been active in the area of nanostructured materials for the last decade, specifically in the topics of magnetism, thermal and mechanical properties, metrology, thermodynamics, thin films, sensors, compositional analysis, sintering, and processes. It has focused on identifying and addressing those topics where key information is missing, where barriers to the application of this new technology exist, and where new standards are necessary. This information is required by U.S. industry if it is to take future advantage of this new class of materials. In order to continue furnishing this assistance to U.S. industry and the scientific community, it is necessary to periodically evaluate R&D activities in nanometer-scale materials outside of the United States. This WTEC report on nanoparticle engineering being sponsored by NIST and many other government funding organizations will provide this update. It is anticipated that this report will also provide the framework for establishing a roadmap for future U.S. research in this area.

The tables and figures on the following pages list the information that NIST would like to obtain from the WTEC report, along with short descriptions of some highlights from previous NIST activity. Included in these highlights are examples of activities designed (1) to develop tools for characterizing materials at the nanometer-size scale, since this size range represents a limit to the applicability of most present equipment; and (2) to focus the broad expertise at NIST on these materials in order to develop an understanding of the physics of the novel properties found in them, since it is not known for many properties whether the new phenomena observed are actually new physics, or are logical extensions of large-scale physics to the nanometer size range. In addition, there has been a significant effort at NIST in the past to identify processing techniques that have the potential to provide large amounts of material, as will be needed for industrial applications. This latter effort was very successful (e.g., development of sol-gel, chemical precipitation, and flame processing techniques, including several patents), so that there should no longer be concern for this new technology of nanometer-scale materials being only a subject of scientific curiosity.

The "Molecular Measuring Machine" being developed at NIST is a good example wherein new metrology is being developed for use with nanometer-scale devices before it becomes a barrier to the technology. As devices are made smaller and smaller, the linewidths of chip features become much smaller, which means that the tolerance for alignment of deposition masks becomes smaller. A barrier to the use of nanometer-sized "powders" is the need to find ways to consolidate them without large amounts of coarsening. NIST has recently studied this effect and found that dynamic compaction may be the solution. NIST is now leading the world in giant magnetoresistance (GMR) spin valves (having the largest GMR values for the smallest switching fields, in all three spin valve structures) and in magnetic nanocomposite refrigerants (possessing 4 times the effect of the best low temperature magnetic refrigerant). Finally, the NIST activity on micromagnetic modeling has shown the need in calculational efforts for the development of "standard problems" and a "standard code," items now being pursued in the micromagnetic community throughout the United States and led by NIST. Ramifications of this finding are now being felt in other calculational activities.

The annual support for NT at NIST amounts to about $4 million per year; $1.0 million is from a direct congressional initiative and the remainder is from other base NIST support.

• Determine Status of Nanometer-Scale Materials, Devices, and Tools
  • Phenomena, Processing, and Characterization

    1. Summarize Present Knowledge and Understanding (U.S. and non-U.S.)
    2. Learn of New Developments
    3. Identify Key Roadblocks
    4. Identify Key People and Groups Working in the Area
    5. List Industrial Applications (Actual and Potential)

  (USE: Help Determine a U.S. Roadmap)

• Assist NIST to Identify Proper Utilization of its Expertise to

  1. Answer Key Questions
  2. Address Unknown Areas
  3. Establish Necessary Databases
  4. Identify Needed Standards (Hierarchical and Materials)
  5. Assess Validity of Results (Traceability)
  6. Promote Technology Transfer to Industry

• Synthesis and Processing (Making Things Small)
  • Electrodeposition, Chemical, Vapor, Mechanical Alloying, Consolidation, Composites, Lithography, Templating, Scanning Probe Techniques

• Characterization (at Nanometer Sizes)
  • SANS, Magnetic, Microscopy (Electron, Atomic Force, Magnetic Force), Composition Profiling, Metrology

• Property Measurement (Materials Phenomena at Small Scales)
  • Magnetic, Electrical, Mechanical, Thermal, Chemical, Optical

J. Unguris, R.J. Celotta, and D.T. Pierce, Phys. Rev. Lett. 67: 140 (1991).

Wear rate as a function of load for a series of electrodeposited Cu-Ni multilayers. The substrate was AISI 52100 steel. Data for electrodeposited nickel and copper is also presented. The wavelength of the multilayers varies from 200 to 7.6 nm.

A.W. Ruff and Zeng-Xiang Wang, Wear, 131, 259 (1989).
A.W. Ruff and D.S. Lashmore, Wear, 151, 245 (1991).

• What are the dislocation generation mechanisms that occur?

• Do dislocations pin at interfaces?
  • Crack tip dislocation emission/interactions?

Calculated entropy change vs temperature for a magnetic field change of 1 tesla for a system of magnetic spins isolated and grouped into clusters as in magnetic nanocomposites. Note the enhancement when clustered. [R.D. McMichael, R.D. Shull, L.J. Swartzendruber, L.H. Bennett, and R.E. Watson, J. Mag. & Magn. Mater. 111, 29 (1992).]

Measured entropy changes (for a field change of 1 tesla) vs temperature for paramagnetic GGG (x = 0) and magnetic nanocomposites GGIC (x ( 0) showing enhanced magnetocaloric effects of the nanocomposites. [R.D. Shull, R.D. McMichael, J.J. Ritter, and L.H. Bennett, MRS Symp. Proc. 286, 449 (1993)].

• Loss of domain structure upon size reduction
  (e.g., shown in the results for film thickness effects in thin film Co)

• Different domain patterns for different demagnetizing methods
  (e.g., shown by the elongated domains when an ac technique is used compared to the curved domains obtained by heating thin film Ni above its Curie Point)

• Different stabilities for different domain wall types upon size reduction
  (e.g., Néel walls forming from Block walls, and transverse walls forming from vortex walls)

• Micromagnetic "Standard Problem" and "Standard Code" development
  (see website http://www.ctcms.nist.gov/~rdm/mumag.org.html)

• NIST has identified nanophase materials as an area of particular focus

• It is interested in coordinating activities with those of other research laboratories

• NIST's role is to assist in accelerating the industrial application of these materials
  • Identify key barriers
  • Provide measurement assistance and leadership
  • Interface closely with industry

			MAGNETIC			TOPOGRAPHIC

5 (m MFM scan of 200 nm Co film on glass, under a 10 nm protective layer of Au. Magnetic image (left) obtained at a lift height of 25 nm.

			MAGNETIC			TOPOGRAPHIC

As in figure above, but Co film thickness reduced to 20 nm.

			MAGNETIC			TOPOGRAPHIC

TMAFM Images

03131257.0f1
3000A Ni on Cu (100) as deposited

			MAGNETIC			TOPOGRAPHIC

TMAFM Images

03131334.0f1
3000A Ni on Cu (100) AC demagnetized

R.D. McMichael and M.J. Donahue, "Head to head domain wall structures in thin magnetic strips," IEEE Trans. MAG, in press.