Properties and Processing of Chemical Vapor Deposited Zinc Sulfide

Persistent Link:
http://hdl.handle.net/10150/194010
Title:
Properties and Processing of Chemical Vapor Deposited Zinc Sulfide
Author:
McCloy, John S.
Issue Date:
2008
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The structure and properties of chemical vapor deposited zinc sulfide (CVD ZnS) were assessed before and after heat treatments, involving different annealing and hot isostatic pressing (HIPing) profiles. Samples were characterized using optical microscopy, SEM, TEM, electron diffraction, polycrystalline and powder x-ray diffraction, x-ray chemical microanalysis, photoluminescence, ultraviolet through longwave infrared transmission, and mechanical testing. Before heat treatment, CVD ZnS consists of lamellar twinned structures in 10 to 100 nm layers aggregated into domains which compose grains typically 5 to 10 μm in diameter with an overall crystallographic texture on the {100} planes. The scattering behavior of CVD ZnS was investigated and described by a surface scattering model based on internal surface roughness and refractive index variations due to onedimensional stacking disorder. The two to five percent hexagonality measured by x-ray diffraction is believed to form due to oxygen impurities at the twin boundaries which cause nanostructural polytypism and result in differential refractive index and scattering. CVD ZnS variants in low temperature deposited red ZnS and sulfur precursor elemental ZnS are examined as well. Color in CVD ZnS is believed to be due to band edge position, probably due to oxygen content, and not directly related to the hydride absorption at 6 μm. After annealing or hot isostatic pressing above 850 °C for sufficient time, CVD ZnS recrystallizes and becomes strongly textured on the {111} planes. This recrystallization is required to remove stacking disorder, resulting in a structure with less than half a percent hexagonality and low visible scattering. The recrystallization is believed to proceed by diffusing the oxygen at the nano-twin boundaries back into the lattice, thus unpinning the boundaries and allowing them to move and grow into the tabular recrystallized morphology by polytype induced exaggerated grain growth. The presence of active metals like platinum, silver, copper, or nickel during hot isostatic pressing causes a reaction with sulfur and lowers the temperature required for recrystallization. The optical scattering model is consistent in describing standard CVD ZnS, elemental ZnS, and multispectral recrystallized ZnS as having successively lower birefringence at internal surfaces.
Type:
text; Electronic Dissertation
Keywords:
zinc sulfide; chemical vapor deposition; infrared window; hot isostatic pressing; scattering; recrystallization
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Materials Science & Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Uhlmann, Donald R.
Committee Chair:
Uhlmann, Donald R.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleProperties and Processing of Chemical Vapor Deposited Zinc Sulfideen_US
dc.creatorMcCloy, John S.en_US
dc.contributor.authorMcCloy, John S.en_US
dc.date.issued2008en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe structure and properties of chemical vapor deposited zinc sulfide (CVD ZnS) were assessed before and after heat treatments, involving different annealing and hot isostatic pressing (HIPing) profiles. Samples were characterized using optical microscopy, SEM, TEM, electron diffraction, polycrystalline and powder x-ray diffraction, x-ray chemical microanalysis, photoluminescence, ultraviolet through longwave infrared transmission, and mechanical testing. Before heat treatment, CVD ZnS consists of lamellar twinned structures in 10 to 100 nm layers aggregated into domains which compose grains typically 5 to 10 μm in diameter with an overall crystallographic texture on the {100} planes. The scattering behavior of CVD ZnS was investigated and described by a surface scattering model based on internal surface roughness and refractive index variations due to onedimensional stacking disorder. The two to five percent hexagonality measured by x-ray diffraction is believed to form due to oxygen impurities at the twin boundaries which cause nanostructural polytypism and result in differential refractive index and scattering. CVD ZnS variants in low temperature deposited red ZnS and sulfur precursor elemental ZnS are examined as well. Color in CVD ZnS is believed to be due to band edge position, probably due to oxygen content, and not directly related to the hydride absorption at 6 μm. After annealing or hot isostatic pressing above 850 °C for sufficient time, CVD ZnS recrystallizes and becomes strongly textured on the {111} planes. This recrystallization is required to remove stacking disorder, resulting in a structure with less than half a percent hexagonality and low visible scattering. The recrystallization is believed to proceed by diffusing the oxygen at the nano-twin boundaries back into the lattice, thus unpinning the boundaries and allowing them to move and grow into the tabular recrystallized morphology by polytype induced exaggerated grain growth. The presence of active metals like platinum, silver, copper, or nickel during hot isostatic pressing causes a reaction with sulfur and lowers the temperature required for recrystallization. The optical scattering model is consistent in describing standard CVD ZnS, elemental ZnS, and multispectral recrystallized ZnS as having successively lower birefringence at internal surfaces.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectzinc sulfideen_US
dc.subjectchemical vapor depositionen_US
dc.subjectinfrared windowen_US
dc.subjecthot isostatic pressingen_US
dc.subjectscatteringen_US
dc.subjectrecrystallizationen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineMaterials Science & Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorUhlmann, Donald R.en_US
dc.contributor.chairUhlmann, Donald R.en_US
dc.contributor.committeememberPotter, Barrett G.en_US
dc.contributor.committeememberSeraphin, Supapanen_US
dc.contributor.committeememberTustison, Randal W.en_US
dc.identifier.proquest2616en_US
dc.identifier.oclc659749604en_US
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