- Cameca SX 100 microprobe with tungsten cathode
- acceleration voltage: 1 kV - 30 kV
- suttle transfer system for air sensitive samples
- anti-contamination system
- Detectors:
back-scattered electron detector,
secondary electron detector (Everhardt-Thornley),
Si-(Li)-detector for determination of energy dispersive x-ray spectra (EDXS)
Four WDX spectrometers with analysator crystals und Ar/Methan proportional counters
- crystals of the wavelenght dispersive x-ray spectrometers:
| crystal |
formula |
lattice-
spacing 2d [Å] |
X-Ray line
K L
|
| LIF |
Lithium fluorid (LiF) |
4.03 |
Sc-Rb |
Te-U |
| PET |
Pentaerythritol (C5H12O4) |
8.74 |
Si-Mn |
Sr-Tb |
| TAP |
Thallium acid phthalate (C8H5O4Tl) |
27.7 |
F-P |
Mn-Nb |
| PC1 |
W/Si Multilayer |
60 |
C-F |
|
| PC2 |
Ni/C Multilayer |
95 |
B-O |
|
| PC3 |
Mo/B4C Multilayer |
200 |
Be-B |
|
The WDXS method on an electron microprobe allows quantify the content of almost all elements (Z > 4) starting from boron. It is assumed that the relative accuracy of 1-3 % for the weight proportion of an element can be realised with well prepared sample surfaces and well defined reference materials. The quantification of elements with small atomic numbers (Z < 11) is often less accurate. The detection limits are in the range 10 – 100 ppm but strongly depend on the actual chemical system. Special attention is paid to select appropriate reference materials which should show properties like mean atomic number, density and weight proportion to that of the sample and on analysis. Pure elements, certified compounds and several own compounds are used for that purpose. Non-certified reference materials are characterised by means of the methods of the competence groups
Structure and
Chemical Analytics. Quantitative calculation of the chemical composition of analysed samples uses matrices correction models PAP [1] or X-φ [2]
which are implemented – for example - in the cameca software package (PeakSight Vers. 5.21). Here, mass absorption coefficients according to tables by K.F.J. Heinrich (mac86, [3]) and B.L.Heneke [4] are used.
local contact: Dipl.-Ing. M. Eckert
[1] J.L. Pouchou, and F. Pichoir, (1984) Rech.Aerosp. 3, 13-38.
[2] C. Merlet; Microchim. Acta (1992) [Suppl.] 12: 107-115.
[3] K. F. J. Heinrich (mac86) Proc. 11th IXCOM, 1987, page 67.
[4] B. L. Henke, P. Lee, T. J. Tanaka, R. L. Shimabukuro and B. K. Fijikawa, Atomic Data Nucl. Data Tables 27, 1 (1982).