X-ray diffraction has been used to measure the intensity profile of the two-dimensional rods of scattering from a single interface buried inside a bulk material. In both $\frac{\mathrm{Si}\mathrm{}\left(111\right)\mathrm{}}{a-\mathrm{Si}}$ and Si(111)/Si${\mathrm{O}}_2$ examples there are features in the perpendicular-momentum-transfer dependence which are not expected from an ideal sharp interface. The diffraction profiles are explained by models with partially ordered layers extending into the amorphous region. In the $\frac{\mathrm{Si}\mathrm{}\left(111\right)\mathrm{}}{a-\mathrm{Si}}$ case there is clear evidence of stacking faults which are attributed to residual 7×7 reconstruction.

• Received 11 August 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.2714