High-resolution X-ray diffraction of silicon-on-nothing

High-resolution multi-crystal X-ray diffraction was employed to characterize silicon-on-nothing samples consisting of a one-dimensional periodic array of buried empty channels. p- and n-type silicon starting wafers were used for sample preparation. For the p- type samples, this periodic array gives rise to well defined Fraunhofer diffraction when the channels are normal to the scattering plane. This indicates good lattice quality of the layer containing the channels. Moreover, the lattices of the surface layer and the layer with the channels were almost indistinguishable from that of perfect silicon. Conversely, the n-type samples showed such lattice tilts and out-of-plane mosaic spreads in the surface and buried layers that Fraunhofer diffraction does not occur from the periodic array of the channels. The elucidation of this different behaviour is in progress and will most likely be fruitful after X-ray images of the same samples are taken.