SI-TASI2 IN-SITU COMPOSITES - A NEW MONOC HROMATOR MATERIAL FOR HARD X-RAYS

The Si matrix of two Si-TaSi2 in situ composites grown in the 111 dire ction have been characterized by means of triple axis diffractometry u sing synchrotron radiation with photon energies of 120 and 160 keV. Th e Si matrix is compressed in the growth direction and dilated along tw o orthogonal directions perpendicular to it. The rocking curves show n o grains or peaksplitting over a large area of the sample, and their f ull width half maximum is of the order of similar to 0.03 degrees. The integrated reflecting power in this energy range is about 400 times l arger than the theoretical value for perfect Si crystals. These proper ties make Si-TaSi2 composites an interesting monochromator material fo r diffraction experiments with hard X-rays when intermediate resolutio n is required. In addition to the properties of the Si matrix, diffrac tion from the TaSi2 rods has been studied. They are highly oriented cr ystals and cause strongly anisotropic deformation in the Si matrix, wh ich opens the possibility of varying the k-space resolution of the dif fractometer merely by tilting the monochromator, and, in the case of a triple crystal diffractometer, by tilting the analyzer crystal as wel l.