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A nanocomposite consisting of PbTe nanocrystals embedded in a silicate glass was studied by small-angle x-ray scattering during the early stage of isothermal annealing at 793 K. A theoretical function based on a model of spherical PbTe nanocrystals surrounded by a Pb and Te depleted shell fits well to all experimental curves. The time dependences of the nanocrystal radius and size of the depleted shell agree with the prediction of the theory of nucleation and growth by the classical mechanism of atomic diffusion.

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We report the fabrication of multilayer structures containing layers of PbTe quantum dots (QDs) spaced by 15–20 nm thick SiO2 layers. The QDs were grown by the laser ablation of a PbTe target using the second harmonic of Nd:YAG laser in an argon atmosphere. The SiO2 layers were fabricated by plasma chemical vapor deposition using tetramethoxysilane as a precursor. The influence of the ablation time on the size and size distribution of the QDs is studied by high-resolution transmission electron microscopy. Optical absorption measurements show clearly the QDs confinement effects.

Pb-and Te-doped borosilicate glasses are transformed by appropriate heat treatment into a composite material consisting of a vitreous matrix in which semiconductor PbTe nanocrystals are embedded. This composite exhibits interesting non-linear optical properties in the infrared region, in the range 10-20 000 A. The shape and size distribution of the nanocrystals and the kinetics of their growth were studied by small-angle X-ray scattering (SAXS) during in situ isothermal treatment at 923 K. The experimental results indicate that nanocrystals are nearly spherical and have an average radius increasing from 16 to 33 A after 2 h at 923 K, the relative size dispersion being time-invariant and approximately equal to 8%. This investigation demonstrates that the kinetics of nanocrystal growth are governed by the classic mechanism of atomic diffusion. The radius of nanocrystals, deduced by applying the simple Efros & Efros [Sov. Phys. Semicond. (1982), 16, 772-775] model using the energy values corresponding to the exciton peaks of optical absorption spectra, does not agree with the average radius determined by SAXS.