SEM / EDX - Imaging Techniques

Imaging Techniques

For the illustration of analyzed samples with up to 100.000 times magnification

Imaging analysis of conducting or semiconducting materials
Imaging analysis of insulators is possible due to thin-film deposition (Au Pd sputtering)
Material contrast (Z contrast) of micro-areas in the BSE mode
Topographic contrast in BSE mode
Local material analysis (e.g. phase identification, element analysis)
Element distribution images (e.g. EDX mapping, line scan)

The following detectors are used for the imaging analysis:

SE detector

Secondary electrons (SE) are low-energy electrons, which are generated by the electron beam. These are accelerated by an electrically-biased grid in the direction of the detector and produce a number of pulses proportionate to their quantity. These pulses are converted into images with greater depth of field and at a higher resolution than a light microscope’s pictures.

BSE detector

Backscattered Electrons (BSE) are beam electrons that are reflected from the surface by elastic scattering depending on the average atomic number (Z) of the material. Heavy elements strongly backscatter electrons, hence those areas appear brighter. Lighter elements tend to absorb electrons and thus appear darker. The BSE image is therefore also called material contrast image (Z-contrast) and allows to draw conclusions about the distribution of chemical materials in the sample. Furthermore the two-section BSE detector can be operated in Subtraction-mode. This produces a topographic contrast, where low-lying areas of the object will appear dark.

Comparison of different modes of operation

Technical equipment

Philips XL 30 TMP
Digital high-performance scanning electron microscope with tungsten filament
Magnification	5x - 400.000x
Resolution	3,5 nm bei 30kV 25 nm bei 1 KV
Beam current	0,4 pA – 4µA max
Detectors	SE detector BSE detectors (classical backscatter- and topographic mode) EDAX - EDX detector
Five-axis motorized sample stage
Sample stage movement Rotation Tilt for large sample maximum height of sample sample chamber	X = 50 mm; Y = 50 mm 360° -15° bis +75° 0° bis 45° 50 mm 284 mm diameter
Vacuum operating range	High vacuum< 5x10-6 mbar

Application examples

Different crystal phases (bright / dark) in a glass	Z-contrast of different phases in the solder
Measurement of a gold layer	electrolytically deposited copper
Carbon Nanotubes (CNTs) on a filter paper fiber [Fa. C-Polymers GmbH]	CNT - PTFE- Compound [Fa. C-Polymers GmbH]
Z-contrast of glass balls in a PA plastic	Z-contrast of glass fibres in a PA plastic