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Univ. Paris-Saclay
Electrical and chemical mapping of silicon pn junctions using energy-filtered X-ray PhotoElectron Emission Microscopy (PEEM)
Maylis Lavayssière
IRAMIS/SPCSI et CEA/LETI
Mercredi 02/03/2011, 09:00

Soutenance à MINATEC, Grenoble

Abstract:

This thesis adresses the problem of imaging of model systems planar silicon pn junctions, fabricated by localized epitaxy, using the novel energy-filtered X-ray PhotoElectron Emission Microscope (XPEEM). The objective is to improve the understanding of the phenomena influencing the XPEEM images of the junctions, with as long-term perspective, a possible application of this method in a complementary way to existing techniques of 2D dopant mapping.

The studies were carried out over three types of junction realized to this purpose and presenting variable electrical field (P+/P, N+/P, P+/N). We firstly developed and optimized a passivation protocol in three-steps which yielded a surface close to flat band conditions. This process allowed us to deduce band alignments as a function of doping level and type on both side of the junction thanks to spectroscopic XPEEM imaging of secondary electrons (to determine local work function), Si 2p core levels and valence band with both laboratory photon sources and synchrotron radiation. Contrast in core-level imaging due to the first atomic layer of the surface was also shown.

Then, we highlighted the role of the lateral electric field across the depletion zone of a pn junction which shifts the apparent position of the latter in PEEM imaging. We compared experimental results and simulations performed with SIMION software to estimate the influence of pn junctions on PEEM imaging. Dark field imaging of the junction was also simulated. Comparison with the experimental results showed that it can be used to localize the real junction.

Keywords:

XPS, XPEEM, spectromicroscopy, silicon doped, synchrotron radiation, work function, valence band, core-level, SIMION, dark-field.

Contact : Nick BARRETT

 

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