| dc.description | There have been attempts to develop room-temperature X- and gamma ray semiconductor
detectors for various applications. The main physical semiconductor properties required for
fabrication of room temperature semiconductor detectors are: (1) high atomic number; (2)
high density; (3) high absorption coefficient; (4) a band gap large enough to keep leakage
currents low, at room temperature and (5) large electron and hole mobility-lifetime products,
for an efficient charge collection [1, 2]. Among these types of detectors, HgI2 has emerged as
a particularly interesting material in view of its wide band gap (2.13 eV) and its large density
(7.5 g/cm3
). HgI2 crystals are composed of high atomic number elements (ZHg=80 and Zi=53)
and with high resistivity (>1014
ficm). These are important factors in applications where
compact and small thickness detectors are necessary for X- and gamma rays measurements.
However, the applications of Hgi2 are limited by the difficulty in obtaining high-quality single
crystals and the long-term reliability problems in devices made from crystals [1].
in this work, the Hgi2 crystals were grown using four different techniques: (a) physical vapor
transport, (b) solution from dimethyl sulfoxide complexes, (c) vapor growth of HgI2
precipitated from acetone and (d) Bridgman method. The obtained crystals for four methods
were characterized considering the following physical chemistry properties: crystal
stoichiometry, crystal structure, plan of the crystal orientation, surface morphology of the
crystal and crystal impurity. The influence of these physical chemistry properties on the
crystals developed by four techniques was studied, evaluating their performance as a radiation
detector. The best result of radiation response was found for the crystal grown by physical
vapor transport. Also, the dependence of the radiation response on the HgI2 crystal purity was
also studied. For this, the HgI2 raw material was purified by the many pass zone refining
technique. A significant improvement in the characteristics of the detector-crystal was
achieved, when the starting materials became purer. | |
