Platelets and inorganic fullerenes on metal surfaces

• Applicant: Professor Dr. Gotthard Seifert
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2003 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5405471

• Final Report Year: 2008

Final Report Abstract

The aim of the project was the test of the suitability of MoS2 and WS2 clusters as building blocks for nanoelectronic devices with the help of density-functional and density-functional-based methods. MoS2 and WS2 particles may be chemically inert and have well-defined band gaps, because it is possible to saturate dangling bonds with additional sulfur atoms. Accordingly, no stabilising ligand shell is necessary, which is insulating and would hamper applications in electronics. In the first and second funding periods three types of small free MnSm clusters were found as stable and very promising candidates: metal-rich "magic" clusters, sulphur-rich platelets, and novel, elongated Chevrel-type clusters with the composition (M3S3)nS2; larger clusters can also adopt a fullerene-shaped hollow structure. Whereas in the second funding period the interaction of MonSm clusters with a gold surface was studied. Based on these investigations during the project was finalized with studies on the contact properties of MoS nanostructures to discover the potential of such structures as novel building blocks for nanoelectronic devices. Indeed, we have shown that certain MoS nanostructures could be ideally transparent for an electron injection. In this way such structures may solve the major drawbacks of usual contacts in molecular electronic devices, like the weak physical bonding between carbon nanotubes and electrodes, as well as difficulties for the current injection from the electrodes into carbon based systems via thiol bonds. Some of the results were already acknowledged in the media, like the News&Views contribution in Nature Nanotechnology, which was an offspring of investigations within this project - see e.g. Frankfurter Allgemeine Zeitung (FAZ) - Natur und Wissenschaft, 21.02.2007. Furthermore, the recent results on the structure of large MoS2 nanostructures were cited in the "Research Highlights" of the recent issue (Vol. 7, March 2008, p. 169) of Nature Materials.

Publications

• "Experimental and theoretical studies on inorganic magic clusters: M4X6 (M = W, Mo, X = O, S)". Chem. Phys. Lett. 396,341 (2004)
  N. Bertram, Y.D. Kim, G. Ganteför, Q. Sun, P. Jena, J. Tamuliene and G. Seifert
  
• "Novel Elongated Molybdenum Sulfide Nanostructures". AIP Conf. Proc. 786, 353-356 (2005)
  S. Gemming, G. Seifert
  
• "Density-functional study of Mo4S6 on Au(111)". Appl. Phys. A 82, 175-179 (2006)
  S. Gemming, G. Seifert
  
• "Electronic and geometric structures of MoxSy and WxSy (x=1, 2, 4; y=1-12) clusters". Appl. Phys. A 82(1), 161-166(2006)
  S. Gemming, J. Tamuliene, G. Seifert, N. Bertram, Y.D. Kim and G. Ganteför
  
• "MonS2n+x clusters - magic numbers and platelets". J. Comp. Mat. Science 35, (2006) 316-320
  G. Seifert, J. Tamuliene and S. Gemming
  
• "Nanoplatelets made from MoS2 and WS2". Chem. Phys. Lett. 418,36-39 (2006)
  N. Bertram , J. Cordes, Y.D. Kim, G. Ganteför, S. Gemming and G. Seifert
  
• J.Phys.Chem., B110 (2006), 25399-25410
  M. Bar-Sadan, A. N. Enyashin, S. Gemming, R. Popovitz-Biro, S. Y. Hong, Y. Prior, R. Tenne, G. Seifert
  
• „Densityfunctional based tight-binding study of small gold clusters". New Journal of Physics 8, (2006) 9
  P. Koskinen, H. Häkkinen, G. Seifert, S. Sanna, Th. Frauenheim, A. Moseler
  
• „Li doped Mo6S6 nanowires: elastic and electronic properties". phys.stat.sol. b 243, 3320-3324 (2006)
  S. Gemming, G. Seifert, I. Vilfan
  
• "Catalysts on the edge - Nanoplatelets of molybdenum sulphide have catalytically active sites along their edges that are promising for desulphurizing fuels". nature nanotechnology 2 (2007) 21
  Sibylle Gemming, Gotthard Seifert
  
• "Self assembly of Mo6S8 Clusters on the Au (111) Surface". Eur. Phys. J. D45 (2007), 439-446
  I. Popov, T. Kunze, S. Gemming, and G. Seifert
  
• "Structural and Electronic Properties of M6X8 Clusters on a Au (111) Surface". Phys. Rev. B 75 (2007) 245436
  I. Popov, S. Gemming, G. Seifert
  
• "Structure and Stability of Molybdenum Sulfide Fullerenes". Angew. Chemie Int. Ed. 46 (2007) 623
  A. N. Enyashin, S. Gemming, M. Bar-Sadan, R. Popovitz-Biro, S. Y. Hong, Y. Prior, R. Tenne, G. Seifert
  
• "Unique Structural and Transport Properties of Molybdenum Chalcohalide Nanowires". Phys. Rev. Lett. 99, 085503 (2007)
  I. Popov, T. Yang, S. Berber, G. Seifert, and D. Tomanek