Undercooling and solidification of metallic-like liquid silicon

• Antragsteller: Professor Dr. Dieter M. Herlach (†)
• Fachliche Zuordnung: Glas und Keramik und darauf basierende Verbundwerkstoffe
• Förderung: Förderung von 2002 bis 2006
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 5397256

• Erstellungsjahr: 2008

Zusammenfassung der Projektergebnisse

An electrostatic levitator was developed to process containerlessly semiconducting droplets of Si, Si-Ge and Si-Co alloys. Droplets in diameter of 2 - 3 mm were deeply undercooled by amounts of about 20% of their melting and liquidus temperatures. The temperature was monitored by contactless pyrometric means and the velocity of the rapidly growing solidification front was monitored by a high speed camera in order to measure the growth velocity as a function of undercooling. The measured growth dynamics was analysed within current theories of solidification of undercooled melts. The results gave evidence for a transition from facetted to non-facetted growth if undercooling exceeds a critical value. In the range of large undercoolings AT > 200 K the growth kinetics of semiconducting Si, Si-Ge and Si-Co could be described by models of dendritic growth. The conclusions from the measurements of growth velocity were supported by the analysis of the microstructures of as solidified samples. For the alloy composed by semiconducting Si and metallic Co an unusual relationship of growth velocity as a function of undercooling, which shows an anomalous change in the temperature dependence at an undercooling of about AT = 170 that cannot be described quantitatively by models of dendritic growth so far. Quantitative measurements of the growth velocity as a function of undercooling deserve as an experimental test of theoretical models for crystal growth in undercooled melts of semiconducting materials. They are directly related to the microstructure evolution of the respective materials and my form an important basis for methods of materials development using computer assisted materials design.

Projektbezogene Publikationen (Auswahl)

• D.M. Herlach, P. Galenko, D. Holland-Moritz, Metastable Solids from Undercooled Melts, Pergamon Materials Series (ed. R. W. Cahn), 2007, ISBN: 978-0-08-043638-8
  
  
• Panofen, C. (01. 06. 2005): Nukleation und Wachstum von reinen Si, Si-Co und Si-Ge Schmelzen. Institutsseminar RS DLR, Köln (D)
  
  
• Panofen, C. (02. 06. 2004): Solidification ofUndercooledPure Silicon and Dilute Silicon- Cobalt Melts. Key Lab. of Eletromagnetic Proc. of Materials, Shenyang (China)
  
  
• Panofen, C. (03. 06. 2005); Solidification of Undercooled Si, Si-Co and Si-Ge Melts. Seminar "Spezielle Probleme der angewandten Festkörperphysik", Institut für Festkörperphysik, Ruhr-Universität Bochum (D)
  
  
• Panofen, C. (07. 06. 2004): Solidification ofUndercooledPure Silicon and Dilute Silicon- Cobalt Melts. Progress-Meeting of German- Japanese Joint Research Projekt of NEDO-DLR on "Magnetic Materials", Sagamihara (Japan)
  
  
• Panofen, C. (28. 04. 2005): Solidification of undercooled Si, Si-Co andSi-Ge melts. Institutsseminar, 1. Physikalisches Institut, RWTH Aachen (D)
  
  
• Panofen, C.; Herlach, D.M. (2006): Rapid Solidification of Highly Undercooled Si and Si-Co Melts. Applied Physics Letters, 88, S. 171913-1 - 171913-4.
  
  
• Panofen, C.; Herlach, D.M. (2007): Solidification of Highly Undercooled Si and Si-Ge Melts. Materials Science and Engineering, 449-451, S. 699 - 703.
  
  
• Panofen, C.; Liu, R. P.; Lohöfer, G.; Herlach, D. M. (08. 03. 2004): Undercooling and Solidification of Liquid Silicon. DPG-Frühjahrstagung, Regensburg (D)
  
  
• Panofen, C.; Liu, R.; Holland-Moritz, D.; Volkmann, T.; Herlach, D.M. (03. 09. 2003): Undercooling and Solidification of Liquid Silicon. EUROMAT 2003, Lausanne (Switzerland)
  
  
• Panofen, C.; Liu, R.P.; Herlach, D.M. (04. 03. 2005): Solidification of Undercooled Si, Si-Co and Si-Ge Melts. 69. Jahrestagung der DPG, Berlin (D)
  
  
• Panofen, C.; Liu, R.P.; Herlach, D.M. (22. 08. 2005): Solidification ofundercooledSi, Si-Co andSi-Ge melts. 12th International Conference on Rapidly Quenched and Metastable Materials, Jeju (Korea)
  
  
• Panofen, C.; Liu, R.P.; Herlach, D.M. (22.09. 2004): Growth Rate Measurements of Undercooled Pure Silicon and Dilute Silicon-Cobalt Melts. Werkstoffwoche, München (D)
  
  
• Panofen, C.; Liu, R.P.; Holland-Moritz, D.; Volkmann, T.; Herlach, D.M. (2004): Undercooling and Solidification of Liquid Silicon. In: Herlach, D.M. [Hrsg.]: Solidification and Crystallization, Wiley-VCH, S. 148 - 156.
  
  
• Wang, Q., Liu, R.P., Qian, Y.Q., Lou, D.C,, Su, Z.B., Ma, M.Z., Wang, W.K., Panofen, C., Herlach, D.M. (2006): Metal-like growth of silicon during rapid solidification by quenching undercooled droplets on a chill plate, Scripta Mater. 54, 37 - 40.