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The semiconductor compounds with high atomic number and wide band gap energy have been investigated as X and gamma range radiation detectors, with high energy resolution, operating at room temperature. The common denominator of semiconductor materials, which operate at room temperature, is the difficulty to grow crystals with high chemical purity and good stoichiometry. The development of this type of radiation semiconductor detectors is still a technological challenge and it has faced many limiting factors, such as: starting material quality compatible for use in crystal growth, low stability of the detector over the time, surface oxidation and other difficulties reported in the literature, which limit their use. In this work, the Physical vapor transport (PVT) methodology for purification and growth of the Iodide Mercury (HgI2) semiconductor crystals was established. HgI2 crystals with crystalline orientation and suitable surface stoichiometry and morphology were obtained by this technique. A significant reduction of impurities after purification could be observed and the impurity levels present in crystals did not interfere in their crystal structures. A good morphology with uniformity in the surface layers of the crystals was found, indicating a good orientation in the crystal structure. A novel study was conducted at the Laboratory of the University of Freiburg, under the guidance of Prof. Michael Fiederle, in order to increase the stability of the HgI2 detector over the time. The application of different types of polymer resins for encapsulation of HgI2 detectors was carried out and studied, in order to protect the HgI2 crystal of reactions with the atmospheric gases and to isolate, electrically, the surface of these crystals. Four types of polymeric resins were evaluated, and each composition is : (a) Resin n◦1: 50% 100% heptane 10% 25% methyl cyclohexane, <1% cyclohexane; (b) Resin n◦2: 25% 50% ethanol, 25% 50% acetone <2.5% ethyl acetate; (c) Resin n◦3: 50% 100% methyl acetate, 5% 10% n-butyl and (d) Resin n◦ 4: 50% 100% ethyl-2cyanoacrylate. The influence of the different types of polymer resins composition, used in the HgI2 detector encapsulation, is clearly demonstrated by the results of the gamma ray spectroscopy. The best results were found for the detector encapsulated with resin n◦3. An increase of up to 26 times in the stability period was observed for the detectors encapsulated with resin, compared to those which were not encapsulated and, therefore, had been exposed to the atmosphere.

Influência de defeitos e da qualidade superficial no desempenho do cristal de iodeto de mercúrio aplicado como detector de radiação