Programm Photovoltaik Ausgabe 2009 ... - Bundesamt für Energie BFE

Strain and residual stress measurements in the Si thin film with EBSD:
A Software titled Cross Court 2 produced by BLG Productions (Bristol, UK) has been acquired for
strain and stress analyses with EBSD. The software allows to measure small rotations and distortions
of electron backscatter patterns obtain from crystalline material. This is achieved by comparing an
EBSD pattern from the target area with one of an unstrained area of the same crystal used as a reference.
The rotations and distortions can be measured to a precision of 0.01° and 10 -4 , dependant of the
quality of the pattern. Given the information about the geometry of the experimental set-up and the
orientation of the crystal lattice the software calculates the distortion tensor which can be broken into
the strain (normal and shear) and rotation tensor. By adding information about the stiffness coefficients
of the crystal, the stress tensor can then be calculated. By using classical EBSD orientation
mapping with the program OIM from EDAX, zones of interest can be located in the grains and selected
for strain and stress analyses with Cross Court.
The preliminary Cross Court measurements show high lattice distortion in the grains with strong intergranular
misorientation due mainly to tensile stress (Fig. 3).
Fig. 3: a) Misorientation gradient EBSD map. The grains show a strong lattice bending
b) Rotation tensor of the profile calculated by Cross Court.
c) Stresses calculation along the profile
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Large grained, low stress multi-crystalline silicon thin film solar cells on glass by a novel combined diode laser and solid phase crystallization process, X. Maeder, Empa
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