FEI Quanta FEG 250, User'S Operation Manual

Page: 168 / 228

System Options: Energy Dispersive X-ray (EDX) Analysis
9-20
GAD EDX ANALYSIS
Maximum detector response is around the 8.5 mm WD, providing an
atomic number contrast, when the resolving power is better than 0.1
(in the Atomic number range around 20).
FIGURE 9-17 X-RAY GAD CONFIGURATION IN ESEM MODE
STEM EDX ANALYSIS
Set the sample surface to 10 mm WD.
Select the area of interest in the STEM mode and perform X-ray
analysis, mapping or line scans as appropriate.
Because the samples are not bulk in nature the beam spread normally
associated with SEM samples is greatly reduced and therefore higher
spatial resolution can be obtained with the STEM detector. This also
provides less background in the spectrum and allows better
separation of peaks as well as more accurate lower count rate
mapping. The high voltage chosen for the analysis still depends
mainly on the composition of the sample.