Structure of PbTe(SiO₂)/SiO₂ multilayers deposited on Si(111)

The structure of thin films composed of a multilayer of PbTe nanocrystals embedded in SiO₂, named as PbTe(SiO₂), between homogeneous layers of amorphous SiO₂ deposited on a single-crystal Si(111) substrate was studied by grazing-incidence small-angle X-ray scattering (GISAXS) as a function of PbTe content. PbTe(SiO₂)/SiO₂ multilayers were produced by alternately applying plasma-enhanced chemical vapour deposition and pulsed laser deposition techniques. From the analysis of the experimental GISAXS patterns, the average radius and radius dispersion of PbTe nanocrystals were determined. With increasing deposition dose the size of the PbTe nanocrystals progressively increases while their number density decreases. Analysis of the GISAXS intensity profiles along the normal to the sample surface allowed the determination of the period parameter of the layers and a structure parameter that characterizes the disorder in the distances between PbTe layers.