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Compound phase formation at Au-Al interfaces
Thesis (M. Sc.) -- University of Stellenbosch, 1995.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613842136104960 |
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| access_status_str | Open Access |
| author | De Waal, Hendrik Schalk |
| author2 | Pretorius, R. |
| author_browse | De Waal, Hendrik Schalk Pretorius, R. |
| author_facet | Pretorius, R. De Waal, Hendrik Schalk |
| author_sort | De Waal, Hendrik Schalk |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (M. Sc.) -- University of Stellenbosch, 1995. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/54681 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:42:33.557Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/54681 Compound phase formation at Au-Al interfaces De Waal, Hendrik Schalk Pretorius, R. Lombaard, J. C. Stellenbosch University. Faculty of Science. Dept. of Physics. Solid state physics Surfaces (Physics) Gold -- Surfaces Aluminum -- Surfaces Interfaces (Physical sciences) Dissertations -- Physics Thesis (M. Sc.) -- University of Stellenbosch, 1995. In this investigation solid state phase formation at gold–aluminium interfaces was studied. From previous work certain questions had remained unanswered which included the following: • What is the first phase to form between Au and Al and in what manner does the Au₅Al₂ and the Au₂Al phases interact during the initial stages of phase formation? • The possible existence of a nucleation barrier to the formation of the AuAl₂ phase, leading to the skipping of this non-congruently melting phase during phase formation. • The formation of what at first looked like a new aluminium rich phase after the formation of Au₅Al₂. Thin-film bilayers of gold and aluminium, both between 500 and 3000 Å thick, were deposited onto a SiO₂-covered silicon substrate using an ultra high vacuum electron beam deposition system. These structures were then heated in a vacuum furnace and analysed using a variety of analytical techniques. These analytical techniques included Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and optical microscopy. A nuclear microprobe was used to carry out micro-beam RBS and alpha-beam Particle Induced X-ray Emission (α-PIXE). It was found that in agreement with the Effective Heat of Formation (EHF) model, the Au₅Al₂ phase was the first phase to form. The EHF model predicts that thermodynamically there is little to choose between the formation of Au₂Al₃ and the Au₅Al₂ as first phases. This could therefore also explain why after the initial formation of Au₅Al₂ the two phases were found to mix and grow together non-uniformly. The introduction of oxygen as an impurity into the aluminium slowed down the reaction rate between the gold and the aluminium and seemed to promote the formation of Au₂Al₃ relative to Au₅Al₂. The kinetics of Au₅Al₂ phase formation was measured using an in-situ dynamic RBS technique. The activation energy was found to be 2.28 eV and the pre-exponential factor was 9.03 cm²/sec. An attempt was made to overcome the nucleation barrier to the formation of the congruently melting AuAl phase by annealing the samples for long periods of time (up to 9 days), at relatively low temperatures (40 to 80 °C). Results seemed to show that at lower temperatures the drop in atomic mobility had a larger effect on phase formation than the decrease in interfacial velocity. RBS showed what at first looked like a new aluminium rich phase, but further X-ray diffraction analysis provided no evidence that a new Au–Al phase was present in these samples. This investigation also showed that under many conditions the gold–aluminium systems tested were very prone to non-uniform growth and void formation. The void formation is visible by SEM as structures which develop on the surface of the sample. The growth of these microstructures was studied in both the SiO₂/Au/Al and the SiO₂/Au/Al configurations as a function of annealing time. A nuclear microprobe was used to do micro-beam RBS and α-PIXE analysis of the structure and composition of the voids. Masters 2012-08-27T11:36:40Z 2012-08-27T11:36:40Z 1995 Thesis http://hdl.handle.net/10019.1/54681 en Stellenbosch University 112 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Solid state physics Surfaces (Physics) Gold -- Surfaces Aluminum -- Surfaces Interfaces (Physical sciences) Dissertations -- Physics De Waal, Hendrik Schalk Compound phase formation at Au-Al interfaces |
| title | Compound phase formation at Au-Al interfaces |
| title_full | Compound phase formation at Au-Al interfaces |
| title_fullStr | Compound phase formation at Au-Al interfaces |
| title_full_unstemmed | Compound phase formation at Au-Al interfaces |
| title_short | Compound phase formation at Au-Al interfaces |
| title_sort | compound phase formation at au al interfaces |
| topic | Solid state physics Surfaces (Physics) Gold -- Surfaces Aluminum -- Surfaces Interfaces (Physical sciences) Dissertations -- Physics |
| url | http://hdl.handle.net/10019.1/54681 |
| work_keys_str_mv | AT dewaalhendrikschalk compoundphaseformationataualinterfaces |