X-Ray Nano-Diffraction on Epitaxial Crystals
Quantum Matter(2014)
摘要
The concept of growing epitaxial Ge and SiGe crystals onto tall
Si pillars may provide a means for solving the problems
associated with lattice parameter and thermal expansion
coefficient mismatch, i.e., dislocations, wafer bowing and
cracks. For carefully tuned epitaxial growth conditions the
lateral expansion of crystals stops once nearest neighbors get
sufficiently close. We have carried out scanning
nano-diffraction experiments at the ID01 beam-line of the
European Synchrotron Radiation Facility (ESRF) in Grenoble on
the resulting space-filling arrays of micron-sized crystals to
assess their structural properties and crystal quality. Elastic
relaxation of the thermal strain causes lattice bending close
to the Si interface, while the dislocation network is
responsible for minute tilts of the crystals as a whole. To
exclude any interference from nearest neighbors, individual Ge
crystals were isolated first by chemical etching followed by
micro-manipulation inside a scanning electron microscope. This
permitted us to scan an X-ray beam, focused to a spot a few
hundreds of nm in size, along the height of a single crystal
and to record three-dimensional reciprocal space maps at chosen
heights. The resolution limited width of the scattered X-ray
beams reveals that the epitaxial structures evolve into perfect
single crystals sufficiently far away from the heavily
dislocated interface.
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