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Overcoming low Ge ionization and erosion rate variation for quantitative ultralow energy secondary ion mass spectrometry depth profiles of Si1–xGex/Ge quantum well structures
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Morris, R. J. H. (Richard J. H.), Dowsett, M. G., Beanland, Richard, Dobbie, A. (Andrew), Myronov, Maksym and Leadley, D. R. (David R.). (2012) Overcoming low Ge ionization and erosion rate variation for quantitative ultralow energy secondary ion mass spectrometry depth profiles of Si1–xGex/Ge quantum well structures. Analytical Chemistry, Vol.84 (No.5). pp. 2292-2298. ISSN 0003-2700
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Official URL: http://dx.doi.org/10.1021/ac202929x
Abstract
We specify the O 2 + probe conditions and subsequent data analysis required to obtain high depth resolution secondary ion mass spectrometry profiles from multiple Ge/Si 1-xGe x quantum well structures (0.6 ≤ x ≤ 1). Using an O 2 + beam at normal incidence and with energies >500 eV, we show that the measured Ge signal is not monotonic with concentration, the net result being an unrepresentative and unquantifiable depth profile. This behavior is attributed to a reduced Ge ionization rate as x approaches 1. At lower beam energies the signal behaves monotonically with Ge fraction, indicating that the Ge atoms are now ionizing more readily for the whole range of x, enabling quantitative profiles to be obtained. To establish the depth scale a point-by-point approach based on previously determined erosion rates as a function of x is shown to produce quantum well thicknesses in excellent agreement with those obtained using transmission electron microscopy. The findings presented here demonstrate that to obtain reliable quantitative depth profiles from Ge containing samples requires O 2 + ions below 500 eV and correct account to be taken of the erosion rate variation that exists between layers of different matrix composition. © 2012 American Chemical Society.
| Item Type: | Journal Article |
|---|---|
| Subjects: | Q Science > QC Physics |
| Divisions: | Faculty of Science > Physics |
| Journal or Publication Title: | Analytical Chemistry |
| Publisher: | American Chemical Society |
| ISSN: | 0003-2700 |
| Date: | 6 March 2012 |
| Volume: | Vol.84 |
| Number: | No.5 |
| Page Range: | pp. 2292-2298 |
| Identification Number: | 10.1021/ac202929x |
| Status: | Peer Reviewed |
| Publication Status: | Published |
| Access rights to Published version: | Restricted or Subscription Access |
| URI: | http://wrap.warwick.ac.uk/id/eprint/44782 |
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