Search

The formation and growth of crystal nuclei of TPA-Silicalite-1 (aluminum free ZSM-5) from clear solns. using TEOS and silicic acid as silica sources were studied with small angle X-ray scattering (SAXS). Information was obtained on the size and shape of nanoscopic precursor particles of silicalite-1. The SAXS data can be interpreted assuming the presence of tablets of 4x2x1.3 nm up to 8x8x1.3 nm depending on the synthesis conditions. Starting solns. have been studied varying the silica source and the cations content (Sodium, Potassium and TPA). In each case well defined particle sizes are obsd. Although the nanoparticles differ in size, their shape is very similar and these data strengthen our hypothesis that TPA-Silicalite-1 formation is a nanoblock based aggregation mechanism rather than growth via monomer addn.

This HREM investigation focuses on the influence of point defects on the final epitaxial relation and atomic interface configuration in a CoSi2/Si(1 0 0) heterostructure. A two-step SPE-MBE grown CoSi2/Si(1 0 0) system is used and, by altering the number of deposited Co monolayers in the template layer, the point defect behavior is studied. We propose a film growth model in which the knowledge about the reconstructed (2 x 1) : Si(1 0 0) surface, the point defect behavior in the presence of an interface, especially a silicide interface, the migration of point defects through a lattice by formation of [1 0 0]-split interstitial (dumbbell) atomic configurations, and a new type of extended defect configurations in diamond type materials will all amalgamate. (C) 1998 Published by Elsevier Science B.V. All rights reserved.