ARC Nanotechnology Network

Distinguished Lecturer Prof Horst Hahn

Since April 2004 Professor Horst Hahn is Managing Director of the Institute for Nanotechnology at the Forschungszentrum Karlsruhe and Director of the Research Laboratory Nanomaterials located at the Technische Universitat Darmstadt and jointly operated by Forschungszentrum Karlsruhe and Technische Universitat Darmstadt. Horst Hahn studied Materials Science at the Universitat des Saarlandes and received his Ph.D from the Technische Universitat Berlin. He was a post doctoral fellow at the Universitat des Saarlandes working in the area of interfaces and nanocrystalline metals. From 1985 to 1987 Dr. Hahn was a Research Associate in the Materials Science Division at Argonne National Laboratory where he established a research program on nanocrystalline ceramics. Subsequently, he was Research Assistant Professor in the Materials Research Laboratory at the University of Illinois at Urbana-Champaign for two years. In 1992 he became Associate Professor of Materials Science at Turgers – The State University of New Jersey. From 1992 to 2004 Horst Hahn was Full Professor (C4) in the Department of Materials Science at Technische Universitat Darmstadt and Head of the Thin Films Division. For three years Professor Hahn served as Chairman of the Department. Professor Hahn is one of the co-founders of SusTech Darmstadt GmbH&Co KG, a start-up company in the area of sustainable chemistry and nanotechnology. The Company is developing products based on functionalized nanoparticulate systems. Horst Hahn is Honorary Professor at the Department of Physics at the University of Hyderabad, India, Distinguished Professor of the IIT Madras, India and Guest Professor at Langzhou University, China. He is a member of the DFG funded Centre for Functional Nanostructures and of the Landeskompetenznetzwerk “Funktionelle Nanostrukturen” at the Universitat Karlsruhe. His main research interests are in the areas of synthesis, characterization and functional (physical and chemical) properties of nanostructured materials in the form of thin films, nanoparticles and bulk materials.


Nanoscience and Nanotechnology: from basic science to applications

The research activities at the Research Center Karlsruhe and at the University Karlsruhe in the area of nanoscience and nanotechnology are concentrated in the following fields: electron transport in nanostructures, nanomaterials, photonics and metamaterials, nanodevices and nanobiology. In these fields the researchers are closely cooperating within the Helmholtz program Key Technologies and the Center for Functional Nanostructures funded by the GermanScience Foundation. A short overview of the activities in Karlsruhe will be presented. Besides the organizational aspects, selected examples of research results will be presented:

  • Recently, the self-organized deposition of single wall carbon nanotubes (CNT) on pre-structured electrode arrays with densities exceeding 106 CNT/cm2 has been demonstrated. Between each electrode pair, a single CNT is arranged by the dielectrophoretic deposition process. All CNT are electrically active which provides the base for future applications in electronics and sensors.
  • The reversible change of physical, mechanical and chemical properties of metallic nanostructures has been shown for nanoporous structures and for thin films exposed to electrolytes. The tunability using an applied potential to control the change of properties is caused by the change of the electron density profile at the surface due to the electrochemical double layer formed in the electrolyte.
  • Energy storage is one of the key aspects of mobility and the use of regenerative energy sources. New nanostructured chemical compounds are developed as hydrogen storage materials in close cooperation of materials scientists, chemists and physicists.


Electronically tunable nanomaterials

The properties of materials are typically controlled in a static manner by the microstructure. This implies control of the grain size, defect concentration, structure and metastability. As long as the microstructure does not change during the use of the material, the properties of the material are fixed, or irreversible. In contrast, in semiconducting materials, properties can be tuned by the application of an external field due to the space charge regions which extend far from the interfaces. In metallic systems, this effect cannot be observed unless the dimensions of the structures are in the nanometer regime. The reason for this different behaviour is the small spatial dimension of the space charge regions due to the effective screening of the induced charges by the conduction electrons. In nanoporous metals and thin films exposed to appropriate electrolytes, it has been demonstrated that substantial changes of physical properties can be induced by the application of a potential between the nanostructured metal and a counter electrode. Examples of the changes of surface stresses and the electrical resistivity of thin Gold films and nanoporous Gold will be presented. A simple model is proposed based on the modification of the electron density distribution at the interface of the metal and the electrolyte. Effectively, the corresponding change of the effective thickness of the sample is the major cause of the observed resistivity change. Additionally, a transparent conducting oxide, ITO, in a nanoparticulate form has been prepared from a dispersion using spin coating. The observed resistivity changes, i.e. the on/off ration can be as large as 2.000, i.e. 200.000 %, between the different values of the control potential. Moreover, the device exhibits field effect transistor behavior identical to a conventional semiconductor, but in this case observed in a material with a large charge carrier density exhibiting metallic conduction behavior. Additionally, the mobility is exceeding 30 cm2/Vs. The device can be used for printable electronics and transparent electronics.

Tour Details:

SYDNEY on Thursday 21st February 2008
Title of talk: Nanoscience and Nanotechnology: from basic science to applications
Location: University of Sydney
Conference Room, S316, Level 3, Mechanical Engineering Building J07
Time: 11:00am
Contact: Teresita Santos (Email)

ADELAIDE on Friday 22nd February 2008
Title of talk: "Electronically tunable nanomaterials"
Location: IAN WARK RESEARCH INSTITUTE, University of South Australia
IWRI Lecture Theatre
Time: 12:00 noon
Contact: Dr. Max Zanin (Email)

MELBOURNE on Friday 29th February 2008
Title of talk: Nanoscience and Nanotechnology: from basic science to applications
Location: Small Technologies Cluster
Conference Room, Small Technologies Cluster, 1 Dalmore Drive, Scoresby, Vic
Time: 9:30am - 12:00 noon
Contact Clive Davenport (Email)

CANBERRA on Monday 3rd March 2008
Title of talk: Nanoscience and Nanotechnology: from basic science to applications
Location: Australian National University
Leonard Huxley Lecture Theatre
Time: 11:00am
Contact: Ilonka Krolikowska (Email)

PERTH on Wednesday 5th March 2008
Location: University of Western Australia