Scanning confocal electron microscopy
Scanning confocal electron microscopy (SCEM) is an electron analogue of scanning confocal optical microscopy (SCOM) where electrons and electron lenses are used instead of light and optical lenses.
Advantages of SCEM
High energies of incident particles (200 keV electrons vs. 2 eV photons) result in much higher spatial resolution of SCEM as compared to SCOM (lateral resolution <1 nm vs. >400 nm).
As compared to conventional electron microscopy (TEM, STEM, SEM), SCEM offers 3-dimensional imaging. 3D imaging in SCEM was expected from the confocal geometry of SCEM, and it has recently been confirmed by theoretical modeling.[1] In particular, it is predicted that a heavy layer (gold) can be identified in light matrix (aluminum) with ~10 nm precision in depth; this depth resolution is limited by the convergence angle of the electron beam and could be improved to few nanometers in next-generation electron microscopes equipped with two fifth-order spherical aberration correctors.[2][3]
Scanning confocal electron microscopes
The idea of SCEM logically follows from SCOM and thus is not new. However, practical design and construction of scanning confocal electron microscope is a complex problem first solved by Nestor J. Zaluzec.[4][5][6][7] His first scanning confocal electron microscope demonstrated the 3D properties of the SCEM, but have not realized the sub-nanometer lateral spatial resolution achievable with high-energy electrons (lateral resolution of only ~80 nm has been demonstrated). Several groups are currently working on construction of atomic resolution SCEM.[8] In particular, atomically resolved SCEM images have already been obtained [9].
References
- ^ K. Mitsuishi, K. Iakoubovskii, M. Takeguchi, M. Shimojo, A. Hashimoto, K. Furuya "Bloch wave-based calculation of imaging properties of high-resolution scanning confocal electron microscopy" Ultramicroscopy 108 (2008) 981
- ^ P. D. Nellist, G. Behan, A. I. Kirkland and C. J. D. Hetherington "Confocal operation of a transmission electron microscope with two aberration correctors" Appl. Phys. Lett. 89 (2006) 124105
- ^ Jeol News Vol. 39, No1, 2004
- ^ N.J. Zaluzec, US Patent # 6,548,810 -0, 2003
- ^ N.J. Zaluzec "The Scanning Confocal Electron Microscope" Microsc. Today 6 (2003) 8 free download
- ^ N.J. Zaluzec "Scanning Confocal Electron Microscopy" Microsc. Microanal. 13 (2007) 1560 free download
- ^ S.P. Frigo, Z.H. Levine, N.J. Zaluzec "Submicron imaging of buried integrated circuit structures using scanning confocal electron microscopy" Appl. Phys. Lett. 81 (2002) 2112
- ^ http://www.materials.ox.ac.uk/peoplepages/nellist.html
- ^ A. Hashimoto et al. "Development of Stage-scanning System for Confocal Scanning Transmission Electron Microscopy" e-J. Surf. Sci. Nanotech. Vol. 6 (2008) 111-114 free download