Synthetic opals made by the Langmuir-Blodgett method

Monodispersive synthetic opal particles were formed by the method of Stober et al. [J. Colloid Interface Sci. 26 (1968) 62] and were made hydrophobic by reacting them with 3-(trimethoxysilyl)propyl methacrylate. Groups of particles were dissolved in chloroform and were spread at the air/water interface using a Nima trough. Each group studied consisted of particles, which had almost identical diameters. Isotherms were obtained and these are illustrated. The use of an optimum value of surface pressure and a high level of hydrophobicity made it possible to deposit good quality multilayers by the Langmuir-Blodgett method but we found that the Langmuir-Schaefer method was easier to use for less hydrophobic particles. The layers obtained were studied by scanning electron microscopy and we present the images obtained from these results

On the physical parameters and crystal defects of bulk semi-insulating InP for radiation detector fabrication

Semi-insulating (SI) InP substrates from various producers have been studied by the Hall technique, X-ray diffraction, laser scattering tomography and photoluminescence. The detection performances of radiation detectors fabricated from selected materials were tested using a 60 keV photon source (241Am). High Hall mobility, low dislocation and precipitation density have been observed in the substrate with low Fe content, which also gave the best detector performances. Its SI properties seem to be controlled by native defects