Abstract
Mercuric iodide crystals in their platelet habit were grown by the polymer controlled vapor transport method. Mercuric iodide 99% in purity was sublimated at temperatures about 122 - 126 °C and vacuum conditions (10-5 mmHg), after selecting an appropriate polymer. Temperature profiles and experimental heat transfer models were determined for two growth furnaces using different insulator configurations for the cold extreme (air, ceramic wool, grilon, copper and ceramic wool). Growth conditions for few and separate nucleation points and large crystals were determined. Representative samples were characterized by optical microscopy and by measuring the current density and apparent resistivity of the material. Future optimization and comparisons with others mercuric iodide crystal growth methods are included.
Highlights
Due to its appropriate physical properties, mercuric iodide is one of the more suitable semiconductor materials for X-ray and Gamma ray detectors operating at room temperature and it is specially useful for low energy X-ray spectrometry[1,2,3,4,5,6,7,8,9]
The most used method to produce mercuric iodide crystals for X-ray detection is growing large crystals by the physical vapor transport method[2,11,12,13,14,15,16,17], and cutting the crystals along the c axis and cleaving perpendicularly to the c axis mechanically, wire-sawn or by hand[18]. This process results in a mechanical damage of the crystal that usually can not be completely repaired by further treatments. Another way to obtain thin mercuric iodide crystals for X-ray detectors is growing them in their platelet habit and no cleavage or surface polishing is needed to fabricate the detector
Mercuric iodide platelets can be grown by the polymer controlled vapor transport method sublimating at temperature bellow the αHgI2-βHgI2 phase transition temperature
Summary
Due to its appropriate physical properties, mercuric iodide is one of the more suitable semiconductor materials for X-ray and Gamma ray detectors operating at room temperature and it is specially useful for low energy X-ray spectrometry[1,2,3,4,5,6,7,8,9]. The most used method to produce mercuric iodide crystals for X-ray detection is growing large crystals by the physical vapor transport method[2,11,12,13,14,15,16,17], and cutting the crystals along the c axis and cleaving perpendicularly to the c axis mechanically, wire-sawn or by hand[18] This process results in a mechanical damage of the crystal that usually can not be completely repaired by further treatments (polishing, etching). Taken the above into account, this report studies the growth of αHgI2 platelets controlled by polymer but maintaining the source temperature bellow the phase α-β transition temperature to assure, theoretically, no transition occurs during the process. Further developing and a comparison with the alternative methods for growing mercuric iodide platelets are considered
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