Electron Probe Microanalysis Laboratory

Capabilities of the Instrument

The electron microprobe offers several operational modes for chemical analysis. These are generally divided into qualitative and quantitative procedures. The qualitative analysis capabilities are briefly listed here :

Qualitative Analysis

Secondary electron imaging

- provides topographic images (surfaces, cracks, voids)
- magnification range from 63X to 10000X
- on-line gray and false-color images
- output in binary data file and PC/Mac 256 color TIFF image file
- image processing software

Backscatter electron imaging

- provides average atomic number contrast images
- magnification range from 63X to 10000X
- on-line gray and false-color images
- output in binary data file and PC/Mac 256 color TIFF image file
- image processing software

Cathodo-luminescence imaging

- provides trace element and lattice dislocation imaging
- magnification range from 250X to 1000X (down to 63X using mosaic imaging)
- on-line gray and false-color images
- output in binary data file and PC/Mac 256 color TIFF image file
- image processing software

Qualitative x-ray imaging

- provides x-ray mapping of sample surfaces for up to 5 elements (WDS)
- provides x-ray mapping of sample surfaces for up to 16 elements (EDS)
- magnification range from 400X to 10000X (down to 63X using mosaic imaging)
- on-line gray and false-color images
- output in binary data file and PC/Mac 256 color TIFF image file
- image processing software

Wavelength spectrometer scanning

- simultaneous wavelength scan acquisition on 5 spectrometers
- on-line database containing over 12,000 entries for peak identification
- publication quality graphical output

Quantitative Analysis

Quantitative analysis generally involves the use of calibration standards and correction for deadtime, background, drift, matrix and interference effects in both the standards and the unknown sample. The following quantitative analysis capabilities are available :

Quantitative element analysis

- simultaneous analysis of 5 elements up to a maximum of 32 elements
- large set of NIST, USNM, USGS, MAS and internal certified analytical standards
- correction of deadtime, background, drift, matrix and interference effects for fully quantitative analysis
- on-line and off-line analysis software includes the CITZAF matrix correction library by John Armstrong (NIST)
- full automation for unknown and standard data acquisition
- results in elemental and oxide weight percent, mole percent, formula atoms and mineral end-members
- statistics on detection limits, sample homogeneity, and analytical sensitivity
- draft and publication quality hard copy and ASCII file output

Quantitative x-ray imaging

- software provides automatic acquisition of rectangular and irregular polygon areas for up to 10,000 analyses
- large area mapping up to 25mm and larger
- output in numerical ASCII file and publication quality contour plot, 3-D surface plot, gray or false color TIFF
- image processing software

Semi-quantitative wavelength shift scanning

- provides semi-quantitative analysis of oxidation states for some elements
- published procedures and results for Fe and S oxidation states