The surface structure of liquid Gold-containing binary eutectic alloys (AuSi, AuGe, AuSn) eutectic alloys

Follow this link and you will find a comprehensive AuSi presentation

Motivation

• Technological importance. These alloys are perfect solders for semiconductor industry.
• Fundamental interest. The surface structure study of liquid binary alloys can be a test for theoretical models.
• In addition, liquid surfaces of pure Au, Si and Ge are hardly accessible for studying due to high vapour pressure, but the eutecic melting temperature is below 400^0 C far below melting points of pure elements.
• Chemical reactions of liquid surfaces of these systems like oxidation are very interesting to study.

Achievements

AuSi and AuGe eutectic alloys have been recently studied at ChemMat-CARS, APS, Argonne, IL. The results were reported at APS User's Meeting 2004, NSLS User's Meeting 2004 and are being prepared for publication.

The main findings are:

• AuSi and AuGe are unique low melting temperature eutectic alloys (compare to melting points of components)
• Low vapor pressure allows UHV studies
• In spite of similarity between two alloys their surfaces have significantly different structure
• Surface form factor of the AuSi eutectic alloy is 20 times higher than for any other studied metallic systems including the AuGe eutectic
• Surface structure of AuSi system can not be explained with models previously developed for pure metals and alloys

Complete story can be found in the poster here [reference]

In addition it is planed to study the structure of AuSi alloy in more details at APS in August 2004 along with the AuSi liquid surface oxidation experiment.

Price Information

Gold-Tin 80%/20% (Alfa-Aesar) 99.99% metal:

• 2.9g - $115 (39.7 $/g)
• 14.5g - $420 (29 $/g)
• 72.5g - $1575 (21.7 $/g)

Gold-Germanium 88%/12% (Alfa-Aesar) 99.85% metal:

• 1g - $85 (85 $/g)
• 5g - $355 (71 $/g)
• 25g - $1575 (63 $/g)

Gold-Germanium 88%/12% (Alfa-Aesar) 99.999% metal:

• 2.9g - $220 (75.9 $/g)
• 14.5g - $830 (57.2 $/g)

Gold-Tin 80%/20% (Goodfellow) :

• 10.4g - $1296 (124.6 $/g)

Gold-Germanium 88%/12% (Goodfellow) :

• 2g - $372 (186 $/g)
• 5g - $659 (131 $/g)

Gold-Silicon 81%/19% (Goodfellow) : Quote

• 50g - $1600 (32 $/g)

Over all, Alfa-Aesar company gives the best prices, however especially for the Gold-Silicon eutectic the Goodfellow has a very good price. I asked Alfa about the same eutectic, got answer that they can do it, but no pricing yet.


Literature

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3. Ellipsometrical studies on the Au/Si(111) system
   Muemmler, K.; Wissmann, P.
   Thin Solid Films 317, 193 (1998)
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    Journal of Applied Physics 48, 420 (1977)
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    Scripta Metallurgica 21, 1689 (1987)
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