John E. Fischer Professor Emeritus Room 409 LRSM (215) 898-6924 fischer@lrsm.upenn.edu Fischer Group Page

Ph.D. Nuclear Science and Engineering, Rensselaer Polytechnic Institute, 1966.
M.S., Mechanical Engineering, California Institute of Technology, 1962.
B.S., Mechanical Engineering, Rensselaer Polytechnic Institute, 1961.


RESEARCH INTERESTS

Fischer’s group uses solid state synthesis, x-ray and neutron scattering, electrical and thermal transport, and other techniques to prepare and study novel nanostructured materials. Experiments are designed to provide fundamental understanding of structure-property relations and to illuminate potential applications.

Carbon nanotubes are tiny seamless cylinders a few nanometers in diameter and many microns long. Believed to be atomically perfect, they exhibit spectacular mechanical and electrical properties. Fischer’s group studies the fundamental properties and potential applications of this new class of materials. Examples include tiny analogs of field effect transistors (the “tubeFET”), electrochemical devices for energy storage, high-strength light weight composites, and hydrogen storage for fuel cell-powered vehicles.

Semiconductor nanowires bear a family resemblance to nanotubes, exhibiting electrical and optical behavior which is determined by the nanoscale diameter and therefore tuneable. The group synthesizes nanowires of elemental, compound and alloy semiconductors and studies their electrical and electro-optical properties. Examples include Si, GaAs, SiGe alloys and large band-gap oxides. Special emphasis is placed on metal/nanowire interfaces in realistic device geometries.

The “burning” of metal carbides in chlorine converts the carbide to chloride, leaving behind a “waste product” of disordered nanoporous carbon. The pore size is tuneable by varying the processing temperature and choice of carbide precursor. We are developing these materials for potential applications in hydrogen storage, Li ion battery anodes, ultracapacitors and selective filtration/permeation membranes.

RECENT PUBLICATIONS

 

“Small angle neutron scattering from single wall carbon nanotube suspensions: evidence of isolated rigid rods and rod networks”, W. Zhou, M. F. Islam, H. Wang, D. Ho, A. G. Yodh, K. I. Winey and J. E. Fischer, Chem. Phys. Letters 384, 185 (2004).

“Single wall carbon nanotube fibers extruded from super-acid suspensions: Preferred orientation, electrical and thermal transport”, W. Zhou, J. Vavro, C. Guthy, K. I. Winey, J. E. Fischer, L. M. Ericson, S. Ramesh, R. K. Saini, V. A. Davis, C. Kittrell, M. Pasquali, R. H. Hauge and R. E. Smalley, J. Appl. Physics 95, 649 (2004).

“A new approach for the preparation of anodes for Li-ion batteries based on activated hard carbon cloth with pore design”, I. Isaev, G. Salitra, A. Soffer, Y. S. Cohen, D. Aurbach and J. E. Fischer, J. Power Sources 119-121, 28 (2003).

“Nanoporous carbide-derived carbons with tuneable pore size”, Y. Gogotsi, A. Nikitin, H. Ye, W. Zhou, J. E. Fischer, B. Ye, H. Foley and M. Barsoum, Nature Materials 2, 591(2003).

“Raman spectroscopy and structure of crystalline GaP nanowires”, Q. Xiong, R. Gupta, K.W. Adu, E. C. Dickey, G. D. Lian, D. Tham, J. E. Fischer and P.C. Eklund, J. Nanosci. Nanotech 3, 335 (2003).

“Thermoelectric power of p-doped single-wall carbon nanotubes and the role of phonon drag”, J. Vavro, M. C. Llaguno, J. E. Fischer, S. Ramesh, R. K. Saini, L. M. Ericson, V. A. Davis and R. E. Smalley, Phys. Rev. Letters 90, 065503 (2003).

“Imaging, structural and chemical analysis of silicon nanowires”, R. Barsotti, Jr., J. E. Fischer, C. H. Lee, J. Mahmood, C. K. W. Adu and P. C. Eklund, Applied Phys. Lett. 81, 2866 (2002).