[Congress Report]Interfaces, thin films, multilayers

I. Kegel (Munich) described the information that can be extracted from semiconductor quantum dots, including vertical ordering in periodic structures and the composition of nanometre scale features. Composition is obtained from measurement of the strain and interference effects of the dot and the underlying substrate, using the variable penetration of grazing incidence scattering. R. Cowley (Oxford) discussed the measurement of roughness at metallic and semiconductor epitaxial interfaces. For Nb on sapphire the roughness worsened with increasing thickness, yet the measured correlation length is increased suggesting that short correlation lengths are well maintained close to the interface. For GaSb on GaAs he found a regular array of dislocations which differ in orthogonal directions indicative of orthorhombic distortion in GaSb.

M. Sanyal (Calcutta) discussed retrieving electron density profiles from specular reflectometry scans using Fourier and iterative fitting methods. Applications to semiconductors and Langmuir-Blodget multilayers were presented including in-depth analyses of lateral correlation lengths. I. Vartanyants (Moscow) presented new developments in reconstructing surface morphology using highly coherent X-ray sources. For a normal source the profile from rough surfaces will be broad and smooth, whereas for a coherent source this will become very jagged due to interference. R. Feidenhans’l (Risø) illustrated methods of analysing interfacial structures from directly bonded Si wafers where small twists create moire patterns or periodic arrays of dislocations and satellites. The satellite structure factors are fitted to a model and the detailed atomic structure can be obtained.

Paul F Fewster