Home > Nanotechnology Columns > FEI > Atomic Scale Imaging Brings New Insight for Materials Science
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William Neijssen Marketing Manager, Quanta FEI Company |
Abstract:
Nanotechnology—the science and technology of the very small (less than 100nm)—will be the most profoundly transforming technology of our era. Skeptics may dismiss the current nano-mania as merely the latest example of über-hype in our over-communicated culture, but nanotechnologies already pervade our lives. The nanorevolution is less about the adoption of some monolithic new technology than it is the realization that almost everything in our lives—in fact life itself—is ultimately controlled by forces and processes that operate at the nanoscale. These atoms and molecules are the fundamental building blocks of our world. But the realization itself is not new. Some two thousand years ago the Greeks first spoke of "atoms", and nearly fifty years ago the noted physicist Richard Feynman may have started the revolution with his often-quoted observation that "there is plenty of room at the bottom."
March 14th, 2007
Atomic Scale Imaging Brings New Insight for Materials Science
Nanotechnology—the science and technology of the very small (less than 100nm)—will be the most profoundly transforming technology of our era. Skeptics may dismiss the current nano-mania as merely the latest example of über-hype in our over-communicated culture, but nanotechnologies already pervade our lives. The nanorevolution is less about the adoption of some monolithic new technology than it is the realization that almost everything in our lives—in fact life itself—is ultimately controlled by forces and processes that operate at the nanoscale. These atoms and molecules are the fundamental building blocks of our world. But the realization itself is not new. Some two thousand years ago the Greeks first spoke of "atoms", and nearly fifty years ago the noted physicist Richard Feynman may have started the revolution with his often-quoted observation that "there is plenty of room at the bottom."
That the nanorevolution has apparently attained critical mass now must be attributed not only to the recognition of its potential value, but also to the availability of tools that allow scientists to explore the world at the nanoscale―and transform their discoveries into products and services offering practical benefits in our everyday lives. FEI is the leading provider of "Tools for Nanotech" specializing in electron and ion beam instruments that allow researchers and developers to visualize, analyze and manipulate materials at the nanoscale. It is noteworthy that Feynman himself identifies the availability of tools, in particular an electron microscope one hundred times more powerful than those available at the time, as a critical prerequisite for the development of nanotechnology. Tools like FEI's new Titan™ TEM with sub-Ångström spatial resolution, are critical enablers of the nanotech revolution today.
Atom by Atom
Ultimately the properties of all materials are determined at the atomic level. It only makes sense that if we want to understand these properties we must be able to see, analyze and eventually manipulate individual atoms. Until recently, TEM has been able to resolve atoms under only very special conditions. Even then, spherical aberration in the magnetic lenses generally blurred the image. Another phenomenon, know as delocalization, interfered with imaging at interfaces, edges and discontinuities within crystalline atomic structures. Unfortunately, these kinds of features are often the most interesting. Now the availability of aberration correctors removes the blurring and delocalization.
Catalysts play an important role in many industrial chemical processes. Often the catalyst is a small solid particle and the catalytic activity takes place at the particle surface. Delocalization in uncorrected TEMs has made detailed observations of the particle surface difficult to obtain. The image below shows the surface of a silver catalyst particle. The locations, and more importantly dislocations, of atoms at the surface are clearly visible. Researchers have suggested that it is these displaced atoms that actually participate in catalysis.
The irregularly placed atoms at the surface of the silver particle are thought to be the locus of catalytic activity. The image is taken on a Titan™ 80-300 TEM with spherical aberration corrector.
In-situ Analysis
An important trend in electron microscopy is the reduction of constraints placed on the sample. Throughout most of its history, these constraints have limited the applicability of electron microscopy to samples that could withstand the vacuum environment required in the instrument. Efforts are now focused on designing systems that permit in situ observations in a near-natural environment, or better still, allow its control as an experimental condition. In the case of the catalyst described above, we know that its catalytic activity is affected by different kinds of pretreatment. In situ TEM might allow direct observation changes in the surface atoms under varying pretreatment conditions.
The recently-introduced Quanta™ 3D FEG is an important advance in in-situ microscopy, designed to allow SEM and STEM imaging under the widest available range of sample conditions, including, vacuum, temperature, humidity and more. It combines a field emission electron column for high resolution imaging with a high current focused ion beam for fast, precise cutting and material deposition. Investigators can use the ion beam to manipulate the sample, perhaps by cutting a cross section to expose subsurface structure or preparing a thin sample for STEM analysis, then observe the sample at high resolution under a range of ambient conditions. Flexibility in the sample environment also relaxes the preparation procedures required in conventional high-vacuum SEM. For instance, the presence of some gas molecules at lower vacuum levels provides a mechanism for neutralizing charge build up that occurs on non-conductive samples under high-vacuum conditions. It also permits direct observation of wet, outgassing, and contaminating samples.
In-situ characterization of microfluidics systems by direct imaging of liquid droplet dihedral angles in the environmental FEG-SEM. Image courtesy of EM-Laboratory University Basel, taken on a Quanta™ FEG SEM.
Conclusion
In spite of the nagging feeling that there may be more sound and fury than significance in the over publicized world of nanotechnology, real applications providing real benefits already exist. Tools that can visualize and manipulate materials at the nano scale will play an essential role in expanding existing applications and developing new ones. Electron microscopy and focused ion beams are among the most flexible tools currently available. New capabilities and continuing improvements, such as the atomic scale imaging and extended sample environments described here, will allow these tools to make an increasingly important contribution to the growth of nanotechnology.
Author: William A. J. Neijssen, BSc. Product Marketing Manager Quanta Series for NanoResearch and Industry, FEI Company, the Netherlands.
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