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Success Stories - The Nanoscale: The Smallest New Big Deal in Measurement
September 01, 2008 , Ottawa, Ontario
You’ll never use this scale to measure anything at home but it could one day be the measure of the tiny technologies that transform our daily lives.
That’s because a team of National Research Council of Canada scientists is developing a measuring tool with regularly spaced nanoscale lines or gratings much like those on a ruler. It could be what many engineers reach for when building nanotechnologies. These length standard artifacts will help guide Canada and the international community into a new age of minute measurement.
The nanometre (billionth-of-a-meter) is the frontier of industrial measurement. Scientists and engineers can already create and manipulate nanoscale devices in their labs, and many computer chips have nanometre-level detail. But there is a major missing ingredient in the nanotechnology revolution—a measurement tool. Scientists and engineers don’t have an easily accessible internationally recognized nanoscale length standard.
It’s a situation reminiscent of the one that led to Canadian Sir Sanford Fleming’s leadership in the creation of International Standard Time. The rise of transcontinental railroads in the 19th century necessitated standardized time in order to make the trains commercially reliable and effective.
“We need to establish traceable and verifiable measurement standards and methods for nanotechnologies,” says Dr. Jennifer Decker, team leader for metrology for nanotechnology at the NRC Institute for National Measurement Standards (NRC-INMS). Dr. Decker is also a participant in the Canadian Advisory Committee to the International Standards Organization (ISO) Technical Committee on Nanotechnologies, in particular the Working Group meetings to determine nanoscale metrology standards and characterization.”
These standards will have a significant commercial impact since they’ll set the rules that everyone will play by. It’s important that Canada is at the table—the countries that participate dictate what the standards will be.”
“It’s all about thinking one step ahead of the developing nanotechnology in order to facilitate commercialization,” says Dr. Mark McDermott, a principal researcher at the NRC National Institute for Nanotechnology (NRC-NINT) and an Associate Professor in the Department of Chemistry at the University of Alberta.
NRC Scientists Measure the (Small) Force
Imagine trying to glue pudding to Styrofoam. The inevitable result: a mess. It’s what NRC scientists are working to avoid at the nanoscale. To do it, they’re building one of the most sensitive small force detectors in the world.
Small forces are those that at the molecular level determine physical characteristics such as adhesion, hardness and elasticity. For large objects that we can see, we can readily measure these qualities. But at the nanometre (billionth-of-a-meter) level, it’s a new world of material properties.
“When you start piecing together nanomaterials, their small force characteristics determine whether you’re going to succeed or fail,” says Dr. Mark McDermott, a principal researcher at the NRC National Institute for Nanotechnology (NINT) and an Associate Professor in the Department of Chemistry at the University of Alberta. “In the emerging field of commercial nanotechnology, it’s critical to be able to measure and characterize these small forces.”
Dr. McDermott is leading a collaborative NRC effort to create one of the world’s most sensitive small force measurement devices. Called an Interfacial Force Microscope (IFM) it will function as an incredibly fine needle that pokes a nanomaterial and records how deep the needle goes (nanoindentation). This will provide detailed measurements of a material’s small force characteristics, and thus how it will behave in relation to other materials.
The research is a core part of an NRC cross-institute project, led in Canada by NRC-INMS, to develop quantifiable measurement standards for nanotechnology.
The IFM project is in collaboration with University of Western Ontario Professor Peter Norton. He’s world-renowned for his work in using IFM in nanotribology to study the nanocharacteristics of interacting surfaces, such as gears, in motion. The NRC-NINT team includes Dr. David Munoz-Paniagua, a former Ph.D. student of Dr. Norton’s, and one of the only people in the world with experience in IFM construction.
“At this level a small difference in length can make a big difference in function. So if materials need to be separated by two nanometres to work, and at 2.1 nanometres the device doesn’t function, you need to be able to measure and control at that level.”
The Canadian nanoscale length standard is being developed through a NRC cross-institute initiative involving four NRC institutes and two universities. Together they have the unique mix of skills and abilities in nanoscale fabrication, instrument design, and metrology.
As envisioned, each measurement standard, (imagine a patch of regularly-spaced lines), will be approximately one square millimetre in size—eight of these grating patches will be fabricated on a silicon chip about one centimetre square. So this length standard chip contains eight gratings ranging in nominal pitch from 150 nanometres to 10 micrometres.
The prototype will be made at the recently established Canadian Photonics Fabrication Center (CPFC), part of the Ottawa-based NRC-Institute for Microstructural Sciences. NRC-IMS scientists use electron beam lithography, which utilizes a precisely controlled beam of electrons to pattern nanophotonic and nanoelectronic devices. This expertise in creating nanoscale devices is being extended by the CPFC that is developing nanoimprint lithography to create a length standard prototype chip. Led by researcher Dr. Frank Shepherd, the group will first use electron beam lithography to make a template, or master, in quartz. This template will be then be used to replicate exact copies of these nanometer grating length standards.
One of the goals of the NRC Metrology for Nanotechnology Program is to determine the extent to which the gratings made by the nano-imprint lithography technique have the same line spacing. It will be metrologists in the dimensional metrology laboratory at NRC-INMS who will be doing the determination.
In the metrology laboratories, an imaging diffractometer was developed to calibrate one-dimensional grating pitch standards: laser light is directed on the grating, the angle of the reflected beam is measured, and the value of the average pitch is calculated. The NRC diffractometer calibrates the average line spacing with an uncertainty much less than the distance between atoms.
Another key tool is the metrological atomic force microscope currently being developed at NRC-INMS by Dr. Brian Eves. Most scanning probe microscopes rely upon calibrated artifacts such as the NRC length standard chip to ensure they correctly measure length. The metrological atomic force microscope will guarantee the correct measured length by using the definition of the metre, based upon the speed of light in a vacuum, as its standard. One of its tasks will be to calibrate line spacings smaller than currently possible with the imaging diffractometer.
Science is such that there will in all likelihood be another generation of nanoscale standards built perhaps on intrinsic standards such as the inter-atomic spacing of crystalline silicon. Dr. Marek Malac at NRC-NINT will be investigating the use of such standards using a transmission electron microscope.
NRC-SIMS research officer Dr. Zou uses force spectoscopy to measure protein unfolding
For now, we need to answer the needs of scientists like Dr. Linda Johnston at the Steacie Institute for Molecular Sciences. Scanning probe microscopes and integrated optical-atomic force microscopes are among the most important tools for the development of nanotechnology. The best instruments enable researchers to image living cells and even the atomic structure of surfaces. For these microscopes to obtain accurate results it is necessary to calibrate them frequently using one-dimensional grating pitch standards. Dr. Shan Zou, NRC-SIMS, will also be working with NRC-INMS to develop artifacts for standard force and distance measurements on soft biological samples.
And with our eye on the economy, and in particular the support of trade and global manufacturing, the grating artifacts will be used to support international comparison experiments. If the pitch value of the artifacts fabricated by nanoimprint lithography can be shown to be essentially identical, then multiple artifacts can be sent simultaneously to National Measurement Institutes around the world, improving the metrological integrity of the comparison exercises—and giving scientists and engineers that all-important easily accessible internationally recognized nanoscale length standard.
