Microanalysis and Microscopy: Capabilities

Fourier Transform Infrared Spectroscopy

FTIR is most often used when there is a need to identify a substance, and is usually applied to organic materials and compounds, but can also be used for some inorganic materials. The technique is typically non-destructive and can be applied to a variety of solids, liquids, crystals, gels, and thin films. Samples are subjected to infrared radiation, which analyzes the molecular structure of the sample to produce an absorption spectrum. This spectrum is then compared to a library of known spectra or, alternatively, the sample may be compared to a standard known material. In doing so, one can identify the organic compounds present. Detection limits for FTIR range from 0.1% to 1% if the compound is a minor component of a sample. It can analyze particles as small as 10 micrometers.

Contact: Michael Lamvik

Scanning Electron Microscopy—High Resolution

SEM is used for viewing, imaging, and analyzing the surface structure of a wide variety of samples, ranging from airborne pollutants to electronic circuits and manufactured parts. It is one of the most useful microscopes, as it can image large and small structures and can be applied to almost any kind of sample with minimal preparation. It produces beautiful images of sample surfaces at a wide range of magnifications. Structures and particles can be measured digitally. Both digital and photographic images can be produced. Using an attached energy-dispersive X-ray spectrometer, the SEM can identify the elements the sample is composed of and can perform elemental mapping (distribution of the various elements in a sample). Elements as light as boron and as heavy as uranium can be quickly identified. Sample size can range from micrometer-sized particles mounted on a smooth substrate to samples several centimeters in size. The high-resolution SEM is capable of magnifying an image in excess of 50,000 times and can resolve particles and structures smaller than 10 nanometers.

Contact: Owen Crankshaw

Scanning Electron Microscopy—Environmental Chamber

The environmental SEM is much like the high-resolution SEM, except that it has a special sample chamber that can tolerate wet or damp samples and is especially suited for imaging organic materials. Structures and particles can be measured digitally, and digital images can be produced. This SEM also has an energy-dispersive X-ray spectrometer for identification of sample elemental composition. Sample size can range from micrometer-sized particles mounted on a smooth substrate to samples several centimeters in size. The environmental SEM is capable of magnifying an image in excess of 20,000 times, can resolve particles and structures smaller than 100 nanometers, and is ideal for looking at samples that interfere with the vacuum system of the high resolution SEM due to outgassing or organic composition.

Contact: Owen Crankshaw

X-Ray Diffraction Analysis

The XRD is used for determining the crystalline structure of anything from minerals to pharmaceuticals. Each substance has a unique way of reflecting X-rays that are beamed at it, and the resultant diffraction pattern can be used to identify unknown substances and combinations of substances in one sample. Libraries of expected responses in the form of spectra are used to compare known responses of standard materials to the results from the unknown substance. RTI’s library database has information on over a quarter million known inorganic and organic substances, and a computerized program to match spectra. This powerful database allows for a myriad of search parameters to be chosen in combinations customizable by the user to determine the identity of unknown materials. The XRD is generally capable of documenting the presence of any component present in the sample at greater than 1%.

Contact: Todd Ennis

Atomic Force Microscopy

The AFM is used to characterize the surface morphology of solid samples. The unique aspect of the AFM is its ability to provide information at atomic dimensions. Sample surfaces (topography must be very flat) are scanned by an extremely fine tip, which when dragged over the surface transmits to the computer an indication of each microtopographical feature, building a virtual image of the sample surface. With a resolution of 1-2 nanometers, AFM is ideal for applications such as surface roughness in the semiconductor industry and for looking at very small particles and structures, especially at the nanometer level. It can also be used for the examination of soft structures such as biological materials or polymers.

Contact: Li Han

Transmission Electron Microscopy

TEM utilizes an electron beam, which passes through a thin sample to reveal its morphological features. It has very high resolution (a few nanometers), so even samples such as viruses and nanofibers can be examined at magnifications exceeding 250,000. The TEM, like the SEM, has an attached energy-dispersive X-ray spectrometer, so the elemental composition of very small individual particles can be determined quickly and easily. The TEM is best suited for very small particles or thin samples and extends the magnification range of the SEM considerably. It can be used for imaging small particles, conducting particle size distribution measurement, determining interparticle relationships such as clumping, and providing elemental mapping (distribution of the various elements in a sample).

Contact: Owen Crankshaw

Optical Microscopy

We have a wide array of optical microscopes that are used to visualize samples at lower magnifications. Using various lighting conditions, our scientists can examine bulk samples using reflected light, can pass light through a thin sample to see how it transmits light, and can use other types of light conditions and angled light to optimize the ability to see very fine morphological details. Stereomicroscopes use reflected light at a wide range of magnifications to reveal surface features and to yield a three-dimensional view of samples such as mineralogical material, biological material, pharmaceutical samples, and others. Transmitted light microscopes (phase contrast, polarized light, and fluorescence) are used to make mineralogical identifications, to conduct particle size distribution analysis, and to view very fine particles or biological structures. Both stereomicroscopes and transmitted light microscopes have digital image capability for rapid capture of high-quality images, and digital video capability. Optical microscopy is often used in conjunction with other microscopy methods, because different instruments, different light conditions, and different magnifications reveal more about a sample than one independent analytical procedure.

Contact: Todd Ennis

X-Ray Fluorescence / X-Ray Photoelectron Spectroscopy

XRF is used for the analysis of bulk samples and provides a rapid, non-destructive, low-cost method for determining the elemental composition of a sample. Bombarding a sample with an X-ray beam and collecting the X-rays that are re-emitted, it is more sensitive than the X-ray spectrometer in the electron microscopes and can detect elements down to the 10-parts-per-million level. It provides a highly quantitative analysis which is very useful when determining such things as the concentration of lead in paint. XPS is similar to XRF, though it measures electrons emitted from the sample instead of X-rays, and thus is more sensitive for determining the elemental composition of only the surface (a few nanometers in depth). XPS, like XRF, is a quick and non-destructive analysis. Because it is very limited in the depth of the sample from which information is gathered, it is particularly useful in the semiconductor industry. Like the X-ray spectrometer in the SEM and TEM, it can also do elemental mapping.

Contact: Andrea McWilliams

Gravimetry

Determination of the mass concentration of airborne particulate matter is performed gravimetrically by weighing and reweighing specialized filters used to collect the samples. Sensitive microanalytical balances are used to record weight differences at the microgram level. Microgravimetry must be done carefully because particles, filters, and microbalances are sensitive to static charge and changes in temperature and humidity. We control static charge with ionizing electrodes and control temperature and humidity in the weighing environment with two dedicated walk-in weigh chambers. This allows us to perform both routine gravimetric determinations and special projects, such as acceptance testing of collection filter media.

Contact: Lisa C. Greene

Photoluminescence Spectroscopy

This technique is a non-destructive method of shining laser light on a sample and analyzing the intensity and spectral content of the light which is reflected by the sample. It is particularly useful in conducting sample quality analysis, such as detection of impurities and defects, and has applications in the detection of drugs or explosives on sample surfaces.

Contact: Jay Lewis

Spectral Ellipsometry

The ellipsometer uses a variable-wavelength light source to reflect light off thin-filmed samples to determine information about the thickness of those films and their optical properties. It can also measure such features as stacked layers within thin films, film roughness, and film porosity. Like XPS, it is a non-destructive technique that has many applications in the semiconductor industry.

Contact: Michael Lamvik

Sample Preparation Facilities

Our sample preparation laboratories allow the preparation of many types of samples prior to microanalysis. We have facilities for microdissection and particle/contaminant isolation or extraction, mineral grinding and milling to extremely fine particle sizes, lapping and polishing of hard samples, and sample thinning prior to TEM analysis. Almost any preparation technique can be accomplished in-house or at associated laboratories.

Contact: Owen Crankshaw