Microscopes are being used to obtain more and more information from a specimen. We are all acquainted with various ways to visualize structures, whether on the surface or embedded within a relatively translucent specimen. There are many ways to “tag” a molecule of interest so that the molecule can be positively identified within the specimen. Traditional microscopes are not able to identify a molecule for us. Other analytical tools are used for that. For example, the nuclear magnetic resonance (NMR) spectrum of a molecular species yields a “fingerprint” that gives a reliable identification. Wouldn't it be great to combine the sensitivity of a state-of-the-art microscope with the molecular analytical capabilities of NMR?

Well you guessed it, this has been done. This approach was first suggested by John A. Sidles at the University of Washington and has recently been demonstrated by Dan Rugar and colleagues at the IBM Almaden Research Center in San Jose.

In today's FTIR market, many instrument manufacturers provide software to perform searches of computer library spectra. With the increased speed of computers running FTIR instruments, you can have the result of a computer library search in literally seconds. However, as we rely more and more on computers in the laboratory we need to keep in mind the limitations and possible areas for error in these applications.

Computer library search programs calculate the difference between the sample spectrum and reference spectrum typically based on peak position and intensity. Different searching algorithms can stress one or the other. The result of a computer search is a Hit List with each hit having a hit quotient index (HQI) to indicate how close that particular spectrum matches the sample spectrum. In some programs the quotient which indicates an exact match would be 1 or 100, in others it is 0.

X-ray microanalysis (EDS) on a SEM or TEM is a valuable tool for research and industry. No other technique can provide so much information so easily about the chemistry of micro-volumes of a material. Many samples require nothing more than positioning of the electron beam onto the area of interest, collecting a spectra, and 30 seconds later you have your answer. Or do you?

Any technique as widespread and straightforward as energy dispersive x-ray spectroscopy is bound to be misused on occasion. It has been my experience that many users either overestimate the capabilities of EDS to answer difficult materials questions or do not fully appreciate the limitations of the technique and how to work around them. These problems tend to show up as the need to analyze increasingly complex samples increases. The following brief description of the physics of electron beam/specimen interaction may be useful in explaining why problems can exist.

The Shared Research Equipment (SHaRE) Program at Oak Ridge National Laboratory (ORNL) provides microanalytical facilities to researchers from U.S. universities, industries, and government laboratories for studies within the materials sciences. SHaRE is one of four microscopy and microanalysis research user facilities supported by the U.S. Department of Energy's Office of Basic Energy Sciences (BES). All BES user facilities, including SHaRE, are available to in order to foster collaborative research, scientific leadership, international competitiveness, and the education of graduate students being prepared for careers in materials science. Based on the scientific excellence and relevance of the proposed experiments, free operating time is available to researchers who then publish their results in open literature. Proprietary research can be accomplished on a full cost-recovery basis or by Cooperative Research and Development Agreements (CRADAs). However, services that can be purchased from commercial laboratories are not appropriate for the SHaRE Program.

Force modulation Imaging is a scanning probe microscopy (SPM) technique that identifies and maps differences in surface stiffness or elasticity. It is one of several new techniques developed as extensions to the basic SPM topographical mapping capabilities. These techniques use a variety of surface properties to better differentiate among materials where topographical differences are small or immeasurable.

Force Modulation Imaging can be used in a wide range of applications including identifying transitions between different components in composites, rubber and polymer blends, evaluating polymer homogeneity, imaging organic materials on hard substrates, detecting residual photoresist on integrated circuits, and identifying contaminants in a variety of materials.

Scanning Probe Microscopy (SPM) was introduced to the scientific community twelve years ago, and its inventors (Binning and Rohrer) were awarded the Nobel Prize in Physics in 1986. In the last decade it expanded from a single technique limited to a single medium of imaging, namely ultrahigh vacuum (UHV) scanning tunneling microscopy (STM), to an array of techniques operating in essentially any medium (vacuum, air or solution with and without electrochemical control). In all of these techniques, a probe, positioned in close proximity to the sample, scans its surface and monitors some property that is related to the surface topography or to any other surface property. Not only can surface structures and properties be investigated at ultrahigh resolution with SPM, but surfaces can also be modified by design. The latter capability is ushering in a new era of nanotechnology.

The traditional method of preparing high quality projection slides of one's best electron micrographs was to “print” negatives onto Kodak 2″ x 2″ emulsified glass slides using a standard enlarger fitted with a reduction lens and then to tray develop the slide to the desired contrast. As A. Kent Christensen pointed out in the June/July 1994 issue of this publication, the cost of 2″ x 2″ slides has become prohibitive. In any event, I always found adjusting the reduction lens on the enlarger to be a major hassle and searching for the correct exposure and developing times to be a ffustratingly inexact experience with much plate wastage.