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The work reports the growth of single BI 3 crystals with platelets habit. Platelets were grown by physical vapor deposition (PVD) in a high vacuum atmosphere and with argon, polymer or iodine as additives. Crystals grew in the zone of maximum temperature gradient, perpendicular to the ampoule wall. Crystals grown with argon as additive show a very shining surface, have hexagonal (0 0 l) faces, sizes up to 20 x 10 mm 2 and thicknesses up to 100 µm. They were characterized by optical microscopy and scanning electron microscopy (SEM). Dendritic-like structures were found to be their main surface defect. SEM indicates that they grow from the staking of hexagonal unities. Electrical properties of the crystals grown under different growth conditions were determined. Resistivities up to 2 x 10 12 Ωcm (the best reported value for monocrystals of this material) were obtained. X-ray response was measured by irradiation of the platelets with a 241 Am source of 3.5 mR/h. A comparison of results according to the growth conditions was made. Properties of the crystals grown by this method are compared with the ones measured for others previously grown from the melt. Also, results for bismuth tri-iodide platelets are compared with the ones obtained for mercuric and lead iodide platelets.

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Films of heavy metal halides (mercuric iodide, lead iodide, bismuth tri-iodide, lead bromide, mercuric bromide and mercuric bromide-iodide), 1" x 1" and 2" x 2" in area, have been grown by physical vapor deposition onto alumina and glass substrates with conductive coatings. From the point of view of film growth the materials was found to have similar behavior, which was evaluated by studying grain size and texture of the films as a function of growth temperature. Films grow oriented with the (0 0 l) crystalline planes parallel or perpendicular to the substrate, according to X-ray diffraction. The influence of film orientation on electrical properties and on response to radiation was evaluated by measuring resistivity and response to X-rays. All the layers give good linearity of response to an X-ray beam. The sensitivity of the layers (signal to dark relation / exposure rate) is maximum (1380) for mercuric iodide. For all the materials, the more oriented the films, the lowest the dark current, and the higher the sensitivity and the signal/dark relation. A superior correlation between electrical and response properties and the layer orientation can be deduced for films of the family of heavy metal halides, observed as a whole.