Next-Generation Nanometrology Program

Meeting the electronics industry's rallying cry for ever smaller and faster components requires more than improvements in manufacturing techniques: engineers must be able to see and measure what they are building.  The limits of conventional imaging have been reached and passed, so NIST is devising new ways to measure and image nanoscale components quickly and easily.  By pushing optical microscopy beyond its traditional limits, improving the speed of non-optical techniques, developing methods for the accurate measurement of nanoparticles (crucial for advanced medicine delivery, among others), determining new calibration standards, and developing accurate methods for measuring 3-D features, this program addresses the measurement challenges of next-generation fabrication.

The next generation of nanotechnology manufacturing will hit a wall without new measurement techniques to image, analyze, and refine the atomically dimensioned devices now being envisioned.  Already, scales are so small that fabrication is beginning to rely on self-assembly, bio-manufacturing, and other methods that require no direct human intervention. Manufacturing on still smaller scales requires a complete overhaul of measurement science -- merely improving current methods will not be enough to meet the challenges. Few companies can spend the necessary time and money brainstorming to creatively meet such long term needs, so NIST, with its expertise in measurement techniques and commitment to providing a competitive edge to U.S. industry as a whole, is addressing the challenge with its Next-Generation Nanometrology Program.

The program has several strategies to develop methods to accurately measure nanoscale features. Current measurement techniques are not only slow -- scanning a sample by sending an electron beam back and forth across it, for example -- but often entail damage or destruction of a product to see its interior.  Current optical microscopes can rapidly examine objects without doing damage, but can only measure features down to about the wavelength of light.  The program will develop advanced optical microscopes using a technique called scatterfield microscopy, which can extract quantitative information from measurements of the angle, polarization and other attributes of light bouncing off a sample.  While this technique does not create images, it can reveal the shape of an object at a scale less than 1/20th the wavelength of light -- close to atomic dimensions.  The grand challenge will be to do this for randomly distributed particles, as opposed to ordered crystals and semiconductors. This would allow determination of the size and distribution of 5 nanometer platinum particles attached to 100 nm carbon particles scattered throughout a fuel cell, for example.

The program also aims to improve non-optical microscopy.  The flagship is the scanning helium ion microscope, a novel instrument related to the scanning electron microscope that scans with a beam of helium ions instead of electrons.  The technique has better resolution than scanning electron microscopy, and can also modify a sample by implanting helium ions or milling away material at the surface to reveal additional features.

The group also focuses on measuring nanoparticles, a challenge that is vital to U.S. industry because of nanoparticles' promise for the pharmaceutical industry along with their possible environmental risks.  NIST is also investigating the “fate of nanoparticles in biological systems” thus developing the accurate dimensional metrology for the environment, health and safety. In addition, NIST is working with Georgetown University Medical Center on studies of 200-nm phospholipid particles that are used to deliver targeted medicines or contrast agents for MRIs and X-rays.  In neither capacity do these particles yet perform consistently.  But it is difficult to analyze their structure with microscopes since their shape deforms when they bind to a surface, such as a microscope slide. NIST will develop better imaging methods and will creatively work around related problems, perhaps by fine-tuning the stickiness of the slide or by learning how to infer the nanoparticle's true properties despite the deformation.

The final program focus represents a jump from NIST's history of creating exact measurement standards to distribute for calibration purposes. Project researchers wish instead to provide measurement methods that allow companies to create their own standards – such as by publishing a “certified” value for some natural standard, like a crystal lattice spacing.  Customers could then prepare their own crystal as a calibration standard.

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• Demonstrated imaging and characterization of intact liposome-based targeted nanoparticle delivery systems by scanning probe microscopy in a fluid imaging environment.  The size, size distribution, functionality, and stability of the delivery system with a payload consisting of a super-paramagnetic iron-oxide contrast agent for magnetic resonance imaging (MRI) were determined and used to improve the transfection efficiency of the formulation.
• Developed an electron microscope image simulator capable of dealing with complex three-dimensional samples.  Electron microscopes used for dimensional measurements have important distortions at the nanometer scale due to the interaction of the beam with the sample.  Understanding and correcting these distortions through the use of the image simulator leads to more accurate measurements.
• Developed in collaboration with other NIST laboratories the new gold nanoparticle size standards: RM 8011, RM 8012, and RM 8013.