Ultra-low voltage scanning electron microscopy
- Oak Ridge National Lab., TN (United States)
- Univ. of Tennessee, Knoxville, TN (United States)
An interesting new opportunity is to perform imaging in the ultra-low energy region between 1eV and 500eV. Over this energy range significant changes in the details of electron-solid interactions take place offering the chance of novel contrast modes, and the rapid fall in the electron beam range leads to the condition where the penetration of the incident beam into the sample is effectively limited to 1 or 2 nanometers. The practical problem is that of achieving useful levels of resolution and acceptable signal to noise ratios in the image. At energies below 1keV chromatic aberration dominates the probe formation in conventional instruments even when using an FEG source. However, the use of optimized retarding field optics essentially maintains chromatic aberration independent of landing energy down to very low values. Figure (1) shows an example of the performance that can be achieved on a commercial instrument - an Hitachi S-4500 - modified to operate in this mode, in this case at 50eV landing energy. The resolution of the image is judged from edge sharpness and detail to be significantly better than 0.1{mu}m and, from experimental observation, this performance is apparently limited by residual astigmatism caused by uncorrected sample charging rather than by fundamental aberrations in the probe forming optics. Comparable, if somewhat lower resolution, ages have been achieved on this, and other FEG SEMs, at energies as low as 1eV.
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 468770
- Report Number(s):
- CONF-960877-; TRN: 97:001308-0024
- Resource Relation:
- Conference: Microscopy and microanalysis 1996, Minneapolis, MN (United States), 11-15 Aug 1996; Other Information: PBD: 1996; Related Information: Is Part Of Microscopy and microanalysis 1996; Bailey, G.W.; Corbett, J.M.; Dimlich, R.V.W.; Michael, J.R.; Zaluzec, N.J. [eds.]; PB: 1107 p.
- Country of Publication:
- United States
- Language:
- English
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