Persistent Link:
http://hdl.handle.net/10150/280235
Title:
The diffusion and segregation coefficient of germanium in silica
Author:
Minke, Mary Ann
Issue Date:
2002
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:
This research was instigated to study non-equilibrium segregation effects during the crystallization of a glass. The non-equilibrium segregation coefficient has been experimentally measured in a variety of alloys including silicon and it has been observed to increase by orders of magnitude as a function of growth rate. Monte Carlo modeling has successfully simulated this effect and has led to the analytical Jackson equation which describes it. Glass crystallization usually takes place far from equilibrium and glasses have the advantage that the glass-crystal interface does not move during quenching, and so the segregation effects can be evaluated at room temperature. The germanium in silica system was chosen for this study because germanium should substitute for the silicon and the glass matrix, and diffuse slowly enough in silica to permit evaluation of the non-equilibrium segregation. Samples were prepared by implanting silica glass with germanium, and then annealing to permit diffusion and to promote crystallization. The samples were analyzed with RBS before and after annealing to determine the distribution of germanium. Initially, the implanted germanium peak was observed to shift towards the surface which is attributed to ion drift in an electric field. This effect was eliminated with a pre-anneal which incorporated the germanium ions into the glass matrix. Since the non-equilibrium segregation depends on the dopant diffusion rate, the diffusion coefficient of germanium in amorphous and crystalline silica was measured. The diffusion coefficient in the silica glass was found to be DG=47exp(-5.8x 10⁴/T) cm²/s and the diffusion coefficient in the silica crystal was found to be DC=360exp(-(6.9x 10⁴/T)) cm²/s . The non-equilibrium segregation coefficient was evaluated based on the distribution of the dopant after crystallization, including the build-up of dopant at the crystal/glass interface. When fitted to the Jackson equation the equilibrium distribution coefficient was found to be k(eq) = 0.01. The non-equilibrium segregation coefficient increased with crystallization rate.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Materials Science.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Materials Science and Engineering
Degree Grantor:
University of Arizona
Advisor:
Jackson, Kenneth

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleThe diffusion and segregation coefficient of germanium in silicaen_US
dc.creatorMinke, Mary Annen_US
dc.contributor.authorMinke, Mary Annen_US
dc.date.issued2002en_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.abstractThis research was instigated to study non-equilibrium segregation effects during the crystallization of a glass. The non-equilibrium segregation coefficient has been experimentally measured in a variety of alloys including silicon and it has been observed to increase by orders of magnitude as a function of growth rate. Monte Carlo modeling has successfully simulated this effect and has led to the analytical Jackson equation which describes it. Glass crystallization usually takes place far from equilibrium and glasses have the advantage that the glass-crystal interface does not move during quenching, and so the segregation effects can be evaluated at room temperature. The germanium in silica system was chosen for this study because germanium should substitute for the silicon and the glass matrix, and diffuse slowly enough in silica to permit evaluation of the non-equilibrium segregation. Samples were prepared by implanting silica glass with germanium, and then annealing to permit diffusion and to promote crystallization. The samples were analyzed with RBS before and after annealing to determine the distribution of germanium. Initially, the implanted germanium peak was observed to shift towards the surface which is attributed to ion drift in an electric field. This effect was eliminated with a pre-anneal which incorporated the germanium ions into the glass matrix. Since the non-equilibrium segregation depends on the dopant diffusion rate, the diffusion coefficient of germanium in amorphous and crystalline silica was measured. The diffusion coefficient in the silica glass was found to be DG=47exp(-5.8x 10⁴/T) cm²/s and the diffusion coefficient in the silica crystal was found to be DC=360exp(-(6.9x 10⁴/T)) cm²/s . The non-equilibrium segregation coefficient was evaluated based on the distribution of the dopant after crystallization, including the build-up of dopant at the crystal/glass interface. When fitted to the Jackson equation the equilibrium distribution coefficient was found to be k(eq) = 0.01. The non-equilibrium segregation coefficient increased with crystallization rate.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Materials Science.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineMaterials Science and Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorJackson, Kennethen_US
dc.identifier.proquest3073285en_US
dc.identifier.bibrecord.b4347309xen_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.