Research.
In broad terms, our activities concern an application of electrostatic field-effect (EFE) concept to control material properties in nonconventional systems with high specific surface area.
The advantage of the EFE control is its tuneability; it allows controlled and reversible change of the carrier concentrations. Especially, field-induced tunable properties of unconventional materials have become a new field of interest opening new possibilities of field-effect devices with reversible modulation of various macro-properties like mechanical, magnetic, transport etc. exploiting the extremely large surface area of nanostructures.
Examples:
Tuning of magnetic properties.
Application of the field-effect principle to control carrier concentration in Strongly Correlated Systems (Electrostatic Doping –ED).
Ø Highly correlated oxide compounds (CMR) with the competing electronic phases with small differences of free energy.
Ø ED induces phase transitions and thus allows the reversible and controllable change of electronic and magnetic properties.
Ø Demonstration of reversible effects (magnetic phase control) induced by applied potential for nanoporous structure
Ø Successful application of field effect in nonconventional system
First demonstration of an all-solid, printable Field Effect Ttransistor (FET) device consisting of conducting nanoparticle channel using electrochemical gating (solid electrolyte)
The merits of the device include:
Ø Higher environmental stability and long-term performance can be ensured compared to the organic TFTs.
Ø The working principle of the device is based on capacitive double layer charging (field effect).
Ø The gel-polymer electrolyte is mechanically stable and reports confirm that no degradation was observed for a time period of two years.
Ø High field-effect mobility.
Ø Easy device fabrication.
Ø Quality dispersion is not required.
Ø Low gate voltage requirement (< 1 V).
Energystorage
The group of Dr. Maximilian Fichtner focuses on energystorage. Further information to the work of this group you find at www.fzk.de/energystorage
Selected literature
1. S. Dasgupta, R. Kruk, H. Hahn, “Electronically tunable nanostructures: metals and conducting oxides” Accepted in Springer Book (September, 2009)
2. S. Dasgupta, S. Gottschalk, R. Kruk, H. Hahn, “A nanoparticulate indium tin oxide field-effect transistor with solid electrolyte gating” Nanotechnology, 19 (2008) 435203
3. S. Dasgupta, R. Kruk, D. Ebke, A. Hütten, C. Bansal, H. Hahn, “Electric field induced reversible tuning of resistance of thin gold films” J. Appl. Phys., 104 (2008) 103707
