Investigation of lattice strains in layered structures containing porous silicon

Silicon layered structures containing porous silicon modified with various thermal treatments and epitaxial layers deposited on porous layers were studied with a number of complementary X-ray diffraction methods using synchrotron source. The methods of characterisation included recording of rocking curves for reflections with various asymmetry as well as projection, section and micro-Laue topography. It was found that oxidising and sintering of porous silicon seriously modified the strains in the porous layer and in some cases even inverting the sense of strain with respect to that in initially formed porous layer. Consequently the deposited epitaxial layer usually was not laterally coherent with the substrate. Some of the investigated layers were not stable in time and after few months period exhibited significant, lost of coherence of porous skeleton.