Home Page Researchers Isaac Balberg

Isaac Balberg

The Racah Institute of Physics
Faculty of Science
The Hebrew University, Jerusalem 91904, Israel
Tel:+972-2-6585680; Fax: +972-2-6584437
E-mail: balberg@vms.huji.ac.il
Website:http://cond-mat.phys.huji.ac.il/balberg/

Basic and applied physics of nanocomposites

Si crystals are the basis of microelectronics. However, because of its special properties Si cannot be applied for optoelectronic devices. On the other hand in the nano scale this is possible and thus the study of Si nanocrystallites became a widely studied subject in recent years. We study here mainly the transport properties of Si nanocrystallite embedded in glass. This has lead to setting the basis for the understanding of the transport properties in the nano Si systems. In recent years the electrical composites that consist of carbon Nanotubes or Graphene particles embedded in polymer matrices have drawn a wide attention both because of the scientific challenges and their promising applications such as the electromagnetic shielding and light airborne electronics. Our study concentrates on understanding their properties from both the basic physics and potential applications points of view.

In our work we try to derive a comprehensive understanding of the transport mechanisms in three dimensional ensembles of Si quantum dots (QDs) that are embedded in an insulating matrix. This understanding is based on our systematic electrical measurements as a function of the density of Si nanocrystallites as well as on a critical examination of the available literature. We conclude that in ensembles of low density QDs the conduction is controlled by quantum confinement and Coulomb blockade effects while in the high density regime the system behaves as a simple disordered semiconductor. In between these extremes the transport is determined by the clustering of the QDs. In view of the clustering two types of transitions in the electrical and optical properties of the system are identified. In order to understand them we introduce the concept of "touching". The application of this concept enables us to suggest that the first transition is a local carrier deconfinement transition, at which the concentration of the non "touching" QDs reaches its maximum, and that the other transition is associated with the onset of percolation in a continuous disordered network of "touching" QDs. It is hoped that our conclusions for the entire possible density range will provide guidance for the discussion and understanding of the transport in ensembles of semiconductor QDs in general and in ensembles of Si and Ge QDs in particular. The very low percolation thresholds in Carbon Nanotube and Graphene polymer composites are of great recent interest. The values of these thresholds are basically determined by the extreme aspect ratios of the carbon particles. However, examining the many data in the literature we found that, surprisingly, for the corresponding composites, the exclusion of the particles positions, due to their ?hard cores?, is very small. We propose that this is associated primarily with the bending of these carbon particles within the actual composites.

Specific research topics related to Nanoscience and Nanotechnology:

  • Semiconductor nano composites.
  • Percolation in systems of nano particles.

List of publications in Nanoscience and Nanotechnology (2011-2012)

  • The electrical transport in three dimemsional ensembles of S. quantum dots, I. Balberg, E. Savir and J. Jedrzejewski, Phys. Rev. B, 83, 035318; 1-14 (2011).
  • Comment on ?Direct measurements of the percolation probability in Carbon Nanofiber-Polyimiide?, I. Balberg, O. Millo, D. Azulay, C. Grimaldi, G. Ambrosetti, Phys. Rev. Lett. Comment, 106, 079701 (2011).
  • Local charging effects in nanocrystalline CdSe films, D. Toker, I. Balberg, O. Zelaya-Angel, E. Savir and O. Millo, Phys. Rev. B, 83, 085303 (2011).
  • Temperature dependence .of the local conductance in nanocrystalline CdSe, D. Toker, I. Balberg, O. Zelaya-Angel, E. Savir and O. Millo, Appl. Phys. Lett, 99, 012102 (2011).
  • Electrical transport mechanisms in three dimensional ensembles of silicon quantum dots, I. Balberg, Leading story of issue 6 (Setember 15), J. Appl. Phys. 110, 061301; 1-26 (2011).(Also, Selected paper by The Virtual Journal of Nanoscience and Nanotechnology).
  • Charge spectroscopy of SiO2 layers with embedded silicon nanocrystals modified by irradiation with high energy ions, I.V. Antonova, S.A. Smagulova, E.P. Neustroev, V.A. Skuratov, J. Jedrzejewski, E.Savir and I. Balberg, Semiconductors, 45, 582-586 (2011).
  • Femtosecond laser induced formation and crystallization of Si nanoclusters in SiOx films V.A. Volodin, T.T. Korchagina, A.K. Gutakovsky, L.I. Fedina, M.A. Neklyudova, A.V. Latyshev, J. Jedrzejewski, I. Balberg, J. Koch, B.N. Chichkov, Physics Express, 2, 5, 1-7 (2012).
  • Enhanced formation of Ge nanocrystals in Ge:SiO2 layers by swift heavy ions, I.V. Antonova, V.A. Skuratov, V.A. Volodin, S.A. Smagulova, D.?. Marin, A. Janse van Vuuren, J. Neethling, J. Jedrzejewski, I. Balberg, J. of Physics D-Applied Physics, 45, 285302; 1-6 (2012).
  • The importance of bendability in the percolation behavior of Carbon Nano Tube and Graphene-polymer composites, J. Appl. Phys. 112, 066104 (2012).
  • Electrical transport in ensembles of semiconductor quantum dots, I. Balberg, invited paper, the International Materials Science Conference, Cancun, August 12-17 (2012) to be published in Physica E.
  • The effects of Confinement and Coulomb Blockade on the transport in ensembles of Si Quantum Dots, I. Balberg, invited paper, the 222 conference of the Electrochemical Society, Honolulu, October 7-15 (2012), to be published in the Conf. Proc.
  • Percolation theory and its application in electrically conducting materials, I. Balberg,, invited chapter in Semiconductor Polymer Composites (Wiley, Berlin, 2012), in press.
  • Manifestation of the quantum confinement effect in phototransport properties of ensembles of semiconductor quantum dots, I. Balberg, invited chapter in Nanostructured Semiconductors from basic research to applications (Panstanford, 2012), in press.
  • The lectrical transport in three dimemsional ensembles of S. quantum dots, I. Balberg, E. Savir and J. Jedrzejewski, Phys. Rev. B, 83, 035318; 1-14 (2011).
  • Comment on ?Direct measurements of the percolation probability in Carbon Nanofiber-Polyimiide?, I. Balberg, O. Millo, D. Azulay, C. Grimaldi, G. Ambrosetti, Phys. Rev. Lett. Comment, 106, 079701 (2011).
  • Local charging effects in nanocrystalline CdSe films, D. Toker, I. Balberg, O. Zelaya-Angel, E. Savir and O. Millo, Phys. Rev. B, 83, 085303 (2011).
  • Temperature dependence .of the local conductance in nanocrystalline CdSe, D. Toker, I. Balberg, O. Zelaya-Angel, E. Savir and O. Millo, Appl. Phys. Lett, 99, 012102 (2011).
  • Electrical transport mechanisms in three dimensional ensembles of silicon quantum dots, I. Balberg, Leading story of issue 6 (Setember 15), J. Appl. Phys. 110, 061301; 1-26 (2011).(Also, Selected paper by The Virtual Journal of Nanoscience and Nanotechnology).
  • Charge spectroscopy of SiO2 layers with embedded silicon nanocrystals modified by irradiation with high energy ions, I.V. Antonova, S.A. Smagulova, E.P. Neustroev, V.A. Skuratov, J. Jedrzejewski, E.Savir and I. Balberg, Semiconductors, 45, 582-586 (2011).
  • Femtosecond laser induced formation and crystallization of Si nanoclusters in SiOx films V.A. Volodin, T.T. Korchagina, A.K. Gutakovsky, L.I. Fedina, M.A. Neklyudova, A.V. Latyshev, J. Jedrzejewski, I. Balberg, J. Koch, B.N. Chichkov, Physics Express, 2, 5, 1-7 (2012).
  • Enhanced formation of Ge nanocrystals in Ge:SiO2 layers by swift heavy ions, I.V. Antonova, V.A. Skuratov, V.A. Volodin, S.A. Smagulova, D.?. Marin, A. Janse van Vuuren, J. Neethling, J. Jedrzejewski, I. Balberg, J. of Physics D-Applied Physics, 45, 285302; 1-6 (2012).
  • The importance of bendability in the percolation behavior of Carbon Nano Tube and Graphene-polymer composites, J. Appl. Phys. 112, 066104 (2012).
  • Electrical transport in ensembles of semiconductor quantum dots, I. Balberg, invited paper, the International Materials Science Conference, Cancun, August 12-17 (2012) to be published in Physica E.
  • The effects of Confinement and Coulomb Blockade on the transport in ensembles of Si Quantum Dots, I. Balberg, invited paper, the 222 conference of the Electrochemical Society, Honolulu, October 7-15 (2012), to be published in the Conf. Proc.
  • Percolation theory and its application in electrically conducting materials, I. Balberg,, invited chapter in Semiconductor Polymer Composites (Wiley, Berlin, 2012), in press.
  • Manifestation of the quantum confinement effect in phototransport properties of ensembles of semiconductor quantum dots, I. Balberg, invited chapter in Nanostructured Semiconductors from basic research to applications (Panstanford, 2012), in press.

Most significant publications in the last five years:

  • A Computer Study of the Percolation Threshold in a Two-Dimensional Anisotropic System of Conducting Sticks, I. Balberg and N. Binenbaum, Phys. Rev. B 28, 3799-3812 (l983).
  • Percolation Thresholds in the Three-Dimensional Sticks System, I. Balberg, N. Binenbaum and N. Wagner, Phys. Rev. Letters 52, 1465-1468 (1984).
  • Excluded Volume and its Relation to the Onset of Percolation, I. Balberg, C.H. Anderson, S. Alexander and N. Wagner, Phys. Rev. B 30, 3933-3942 (l984).
  • Tunneling and Nonuniversal Conductivity in Composite Materials, I. Balberg, Phys. Rev. Letters, 59, 1305-1309 (l987).
  • Deposition of Device Quality, Low H Content Amorphous Silicon, A.H. Mahan, J. Carapella, B.P. Nelson, R.S. Crandall and I. Balberg, J. Appl. Phys. 69, 6728-6730 (1991).

Colaborations:

Within the Hebrew University:
  • Prof. Oded Millo, Racah Institute of Physics
  • Prof. Amir Sa'ar, Racah Institute of Physics
In Israel:
  • D. Cahen (Weizmann)
  • Prof. Y. Rosenwaks (TAU)

Research grants

  • ISF (2010-2013) Prof. O. Millo and Prof. I. Balberg
  • Ministry of Science (2012-2013) Prof. I Balberg

Students, postdocs and researchers

Staff  scientists: Dr. Ester Savir and Dr. Jedrzej Jedrzejewski.
Postdocs: Dr. Doron Azulay.
M.Sc students: Guy Ravid

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