Surface diffusion: A computer study of its effects on thin film morphology.

Persistent Link:
http://hdl.handle.net/10150/185225
Title:
Surface diffusion: A computer study of its effects on thin film morphology.
Author:
Sargent, Robert Bruce.
Issue Date:
1990
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:
A two-dimensional hard-disk model of thin-film deposition is described; it is of the type originally introduced by Henderson, Brodsky, and Chaudhari (1974). We have implemented a simple (and necessarily approximate) way to incorporate the effects of surface diffusion in our model, and a means to connect the input parameters of the computer algorithm to the evaporation parameters of substrate temperature and evaporation rate. In the limit of no surface diffusion (low substrate temperature), the model predicts a dendritic structure with large voids; this is the Henderson model. With sufficient surface diffusion (higher substrate temperature), a structure of closely packed crystallites is predicted, and the root-mean-square surface roughness is less than half that predicted by a Henderson-type simulation. This dependence of microstructure on substrate temperature is similar to a zone transition originally described by Movchan and Demchishin (1969) in metal and oxide films. We consider the effect of changing the angle of vapor incidence from normal to oblique. As this angle is increased, a certain critical angle is reached, at which the film density drops and the surface roughness rises precipitously. Both effects result from large columnar voids that develop; the structure of the material that comprises the columns between the voids is similar to the structure of depositions simulated at normal vapor incidence. In a separate study, we simulate the growth of a thin film in two dimensions with a computer implementation of the molecular dynamics (MD) method. The system consists of a krypton substrate maintained at a temperature of 10 degrees Kelvin, toward which argon atoms are periodically directed (with a velocity corresponding to 120 degrees Kelvin). The resulting argon film follows the (horizontal) spacing of the krypton lattice until the thickness approaches an average thickness of about ten monolayers. As deposition proceeds, the configuration of the film changes to incorporate an edge misfit dislocation at the film-substrate interface; this relieves the interfacial stress. We also apply the MD method to study the relaxation of thin-film structures predicted by the hard-disk growth model.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic; Optics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Optical Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Macleod, Angus

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleSurface diffusion: A computer study of its effects on thin film morphology.en_US
dc.creatorSargent, Robert Bruce.en_US
dc.contributor.authorSargent, Robert Bruce.en_US
dc.date.issued1990en_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.abstractA two-dimensional hard-disk model of thin-film deposition is described; it is of the type originally introduced by Henderson, Brodsky, and Chaudhari (1974). We have implemented a simple (and necessarily approximate) way to incorporate the effects of surface diffusion in our model, and a means to connect the input parameters of the computer algorithm to the evaporation parameters of substrate temperature and evaporation rate. In the limit of no surface diffusion (low substrate temperature), the model predicts a dendritic structure with large voids; this is the Henderson model. With sufficient surface diffusion (higher substrate temperature), a structure of closely packed crystallites is predicted, and the root-mean-square surface roughness is less than half that predicted by a Henderson-type simulation. This dependence of microstructure on substrate temperature is similar to a zone transition originally described by Movchan and Demchishin (1969) in metal and oxide films. We consider the effect of changing the angle of vapor incidence from normal to oblique. As this angle is increased, a certain critical angle is reached, at which the film density drops and the surface roughness rises precipitously. Both effects result from large columnar voids that develop; the structure of the material that comprises the columns between the voids is similar to the structure of depositions simulated at normal vapor incidence. In a separate study, we simulate the growth of a thin film in two dimensions with a computer implementation of the molecular dynamics (MD) method. The system consists of a krypton substrate maintained at a temperature of 10 degrees Kelvin, toward which argon atoms are periodically directed (with a velocity corresponding to 120 degrees Kelvin). The resulting argon film follows the (horizontal) spacing of the krypton lattice until the thickness approaches an average thickness of about ten monolayers. As deposition proceeds, the configuration of the film changes to incorporate an edge misfit dislocation at the film-substrate interface; this relieves the interfacial stress. We also apply the MD method to study the relaxation of thin-film structures predicted by the hard-disk growth model.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academicen_US
dc.subjectOptics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineOptical Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMacleod, Angusen_US
dc.contributor.committeememberDeymier, Pierreen_US
dc.contributor.committeememberBovard, Bertranden_US
dc.identifier.proquest9108426en_US
dc.identifier.oclc708645883en_US
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