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Second Ion Mass Spectrometry (SIMS)

Secondary Ion Mass Spectrometry (SIMS) is well established as a powerful tool for chemical surface-, interface- and thin film analysis. One advantage of SIMS is that it is able to detect the isotopes of all elements, including hydrogen. Detection limits in the ppm-level are usually obtained, the limits reaching down to the ppb-level in special cases.


SIMS is based on the mass spectrometric analysis of secondary ions, which are sputtered - together with neutral atoms and molecules - due to primary particle bombardment of the sample surface in vacuum. The resulting erosion process enables the detection of element concentrations as a function of the eroded depth, leading to so called depth profiles. The attainable depth resolution of 2-5 nm, only surpassed by Transmission Electron Microscopy, distinguishes SIMS as an outstanding method for the analysis of thin films and layered structures as used in thin film solar cells.


For research and development at the IEK 5-Photovoltaics, SIMS is applied in the scope of material science - e.g. for the investigation of diffusion and segregation processes - as well as in the scope of technological developments, e.g. for the detection of dopants or detrimental impurity contaminations incorporated during film deposition. Furthermore, the SIMS analysis of completely processed solar cells is of increasing importance because it enables the correlation of chemical information with the opto-electronic properties of the devices.


At the IEK5-Photovoltaics, an ultra-high vacuum (residual gas pressure < 10-10 mbar) SIMS equipment with quadrupol mass spectrometers is used. This type of instrument enables the extensive variation of analysis parameters, which is necessary to attain meaningful results concerning the analytical questions described above.


Operation modes:


depth profiles, lateral element distributions (ion images), 3D-analysis, mass spectra, secondary ion energy distribution


Instrument specification:


primary ions O2+, Cs+
primary ion energy 1 - 15 keV
angle of incidence 0 - 85°
beam diameter 1 – 50 µm
secondary ions 1 – 250 amu, positively or negatively charged
charge compensation 0.3 – 5 keV electrons

BauelemEntw05SIMS measurement setup for chemical analysis of surfaces, interfaces and thin films.

Contact:

Dipl.-Ing. Uwe Zastrow
Dr. Tsvetelina Merdzhanova


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