| dc.description.abstract | The PV industry requires high-purity quartz for the production of crucibles
for mono crystalline silicon production. Even the smallest
amounts of impurities can degrade the performance of
photodiode wafers, therefore a very high purity of the the contacting quartz crucible is necessary.
The capabilities of modern TEM for the investigation of high-purity quartz and the detection of inclusions and impurities are explored on industrial quartz sand and bulk rock quartz TEM specimens.
The standard tripod polishing routines are optimized to acquire contamination free, site-specific, large area bulk specimens.
The problem of specimen charging is overcome by using quartz sand carbon grid specimens or relying on scanning TEM techniques.
SPED is found to allow the investigation of crystalline features with maximized information yield by minimal dose.
TEM, STEM, SPED, EDX and EELS are utilized for the detection of inclusions. As no impurities were identified, it is concluded
that the ppm level impurities measured with other methods are lattice bound or interstitial trace elements.
Aberration corrected ABF and HAADF HR STEM are applied and the first ever single atom column resolved ABF STEM lattice imaging of quartz with are resolution of $\sim$ 1 \r{A} is reported.
Beam damage, inducing a crystalline to amorphous transition, the main limitation for TEM investigation of quartz, is characterized. The critical dose until amorphization is found to be dependent on thickness, crystal orientation and imaging technique. The critical dose for fine probe STEM is measured to be
$10.6\pm2.6 \cdot 10^{24}\frac{e}{m^2}$ at 80 nm thickness and for broad probe STEM $2.31\pm0.06 \cdot 10^{24}\frac{e}{m^2}$ at 50 nm thickness. | en |
