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CdZnTe is one of the most exploited materials for the realization of room temperature X- and gamma- ray detectors. However the final cost of the devices remains a limiting factor for large-scale applications. One of the problems is connected with the realization of contacts. Due to the difficulty to obtain large single wafers, usually photolithography is carried out for each single device, strongly increasing the cost of detector fabrication. On the other side because of the important role played by the metal-CZT interface on the functioning of the final device, a special attention should be paid to the technology employed in the realization of metal contacts. Recently, a novel, reproducible and low-cost method for gold deposition on CZT surface has been developed [1] combining two different technologies: scanning pipette technique and electroless deposition. With this technique it is possible to avoid the photolithography process and still obtain complex contact patterns with a good spatial resolution and high reproducibility. In this work, it is shown that contacts with dimensions down to a few tenths of microns can be obtained. The contacts show good mechanical stability and optimal current-voltage characteristics. High-resolution CZT detectors have also been demonstrated by the use of this technology. Moreover, the technology is shown to be easily adapted to the deposition of other metals than gold, for example platinum or palladium, by simply changing the deposited solution.

CdZnTe crystals are employed for the preparation of X-ray and gamma-rays detectors. Control of seeding and interface shape must be improved in order to increase the yield of good quality single crystalline crystals. Zinc is used to partially substitute cadmium in the cation site mainly to increase material resistivity. However, zinc segregation in the melt is one of the causes of material non-homogeneity. On the other hand, the segregation of zinc offers a unique chance for studying the growth interface shape after growth. Several CdZnTe crystals were grown by vertical Bridgman. A few crystals were grown in standard closed ampoules. In other cases, the melt was encapsulated by boron oxide during growth, and in others melt and vapour were separated by a quartz disk floating on melt. The zinc distribution and the growth interface shape were studied by photoluminescence mapping on slices cut parallel to the growth axis. Two aspects were mainly studied. The first one concerns with the possibility to obtain a convex interface shape during the whole growth. In fact it is known that in the case of CdZnTe crystals it is unlikely to obtain convex interface shape due to the low thermal conductivity of both the solid and the melt. Results show that this is true in the case of standard vertical Bridgman, but convex interface is actually achieved in the case the vapour phase is separated by the melt (by boron oxide or a quartz disk). In these cases melt flow is modified and so the temperature distribution at the growth interface. The second aspect concerns the zinc distribution in the first to freeze part of the crystal. This is influenced by the effect of supercooling that is unavoidable in the case of unseeded vertical Bridgman growth. However, experimental results could be explained only if solid state thermal migration of zinc and the effects of multi-nucleation sites are taken into account.

CdZnTe crystals are employed for the preparation of X-ray and gamma ray detectors. Control of seeding and interface shape must be improved in order to increase the yield of good quality single crystals. Zinc is used to partially substitute cadmium in the cation site mainly to increase material resistivity. However, zinc segregation in the melt is one of the causes of material non-homogeneity. On the other hand, the segregation of zinc offers a unique chance for studying the growth interface shape after growth. Several CdZnTe crystals were grown by vertical Bridgman. A few crystals were grown in standard closed ampoules. In other cases, the melt was encapsulated by boron oxide during growth, and in others melt and vapour were separated by a quartz disk floating on melt. The zinc distribution and the growth interface shape were studied by photoluminescence mapping on slices cut parallel to growth axis. Two aspects were mainly studied. The first one concerns with the possibility to obtain a convex interface shape during the whole growth. In fact it is known that in the case of CdZnTe crystals it is unlikely to obtain convex interface shape due to the low thermal conductivity of both the solid and the melt. Results show that this is true in the case of standard vertical Bridgman, but convex interface is actually achieved in the case the vapour phase is separated by the melt (by boron oxide or a quartz disk). In these cases melt flow is modified and so the temperature distribution at the growth interface. The second aspect concerns the zinc distribution in the first to freeze part of the crystal. This is influenced by the effect of supercooling that is unavoidable in the case of unseeded vertical Bridgman growth. However, experimental results could be explained only if solid state thermal migration of zinc and the effects of multi-nucleation sites are taken into account.

Radiation detection is a very important tool for every application field that includes monitoring and detection of radiation sources. In the case of gamma and X-ray detectors, a wide number of application fields are involved in the detector developing, this list comprehends medical imaging, environmental monitoring, homeland security and astrophysics. In recent years CdZnTe(CZT) has emerged as an interesting material for the realization of room temperature X- and gamma ray detectors. In this work IMEM grown CZT ingots and detectors were studied with several techniques, in order to understand the mechanisms occurring in the device functioning. The results were pushed together to create a direct feedback with the crystal growers of the group.