Abstract
We report on the characterization of high quality sapphire single crystals suitable
for high-resolution X-ray optics at high energy. Investigations using rocking curve
imaging reveal the crystals to be of uniformly good quality at the level of ~10-4
in lattice parameter variations, deltad/d. However, investigations using backscattering
rocking curve imaging with lattice spacing resolution of deltad/d ~ 5.10-8 shows very
diverse quality maps for all crystals. Our results highlight nearly ideal areas with
edge length of 0.2-0.5 mm in most crystals, but a comparison of the back re
ection
peak positions shows that even neighboring ideal areas exhibit a relative difference
in the lattice parameters on the order of deltad/d = 10-20.10-8; this is several times
larger than the rocking curve width. Stress-strain analysis suggests that an extremely
stringent limit on the strain at a level of ~100 kPa in the growth process is required
in order to produce crystals with large areas of the quality required for X-ray optics
at high energy.
