Simulation and growth of cadmium zinc telluride from small seeds by the travelling heater method

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dc.contributor.authorRoszmann, Jordan Douglas
dc.contributor.supervisorDost, Sadik
dc.date.accessioned2016-06-21T14:48:18Z
dc.date.available2017-06-11T11:22:05Z
dc.date.copyright2016en_US
dc.date.issued2017-06-08
dc.degree.departmentDepartment of Mechanical Engineeringen_US
dc.degree.levelDoctor of Philosophy Ph.D.en_US
dc.description.abstractThe semiconducting compounds CdTe and CdZnTe have important applications in high-energy radiation detectors and as substrates for infrared devices. The materials offer large band gaps, high resistivity, and excellent charge transport properties; however all of these properties rely on very precise control of the material composition. Growing bulk crystals by the travelling heater method (THM) offers excellent compositional control and fewer defects compared to gradient freezing, but it is also much slower and more expensive. A particular challenge is the current need to grow new crystals onto existing seeds of similar size and quality. Simulations and experiments are used in this work to investigate the feasibility of growing these materials by THM without the use of large seed crystals. A new fixed-grid, multiphase finite element model was developed based on the level set method and used to calculate the mass transport regime and interface shapes inside the growth ampoule. The diffusivity of CdTe in liquid tellurium was measured through dissolution experiments, which also served to validate the model. Simulations of tapered THM growth find conditions similar to untapered growth with interface shapes that are sensitive to strong thermosolutal convection. Favourable growth conditions are achievable only if convection can be controlled. In preliminary experiments, tapered GaSb crystals were successfully grown by THM and large CdTe grains were produced by gradient freezing. Beginning with this seed material, 25 mm diameter CdTe and CdZnTe crystals were grown on 10 mm diameter seeds, and 65 mm diameter CdTe on 25 mm seeds. Unseeded THM growth was also investigated, as well as ampoule rotation and a range of thermal conditions and ampoule surface coatings. Outward growth beyond one or two centimeters was achieved only at small diameters and included secondary grains and twin defects; however, limited outward growth of larger seeds and agreement between experimental and numerical results suggest that tapered growth may be achievable in the future. This would require active temperature control at the base of the crystal and reduction of convection through thermal design or by rotation of the ampoule or applied magnetic fields.en_US
dc.description.proquestcode0346en_US
dc.description.proquestcode0794en_US
dc.description.proquestcode0548en_US
dc.description.proquestemailjordan.roszmann@gmail.comen_US
dc.description.scholarlevelGraduateen_US
dc.identifier.urihttp://hdl.handle.net/1828/7347
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.rights.urihttp://creativecommons.org/licenses/by/2.5/ca/*
dc.subjectCadmium Tellurideen_US
dc.subjectCadmium Zinc Tellurideen_US
dc.subjectTravelling Heater Methoden_US
dc.subjectCompound Semiconductorsen_US
dc.subjectCrystal Growthen_US
dc.subjectSolution Growthen_US
dc.subjectThermosolutal Convectionen_US
dc.subjectFinite Element Analysisen_US
dc.subjectComputational Fluid Dynamicsen_US
dc.subjectDeal.IIen_US
dc.subjectLevel Set Methoden_US
dc.subjectGallium Antimonideen_US
dc.subjectZone Refiningen_US
dc.subjectVertical Gradient Freezingen_US
dc.subjectStefan Problemen_US
dc.subjectCylindrical Coordinatesen_US
dc.subjectNatural Convectionen_US
dc.subjectRadiation Detectorsen_US
dc.subjectBulk Crystal Growthen_US
dc.subjectCZTen_US
dc.subjectDiffusivityen_US
dc.subjectDissolutionen_US
dc.subjectTelluriumen_US
dc.subjectCadmiumen_US
dc.subjectEnrichment by Virtual Interface Eliminationen_US
dc.titleSimulation and growth of cadmium zinc telluride from small seeds by the travelling heater methoden_US
dc.typeThesisen_US

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