[nano501] nano 501 Tutorial, Wednesday Jan. 16, 2:30 pm EE 317

[Goodman, Alicia D.]

Multiphases Gallium Nitride Nanowires and Nanocircuits
Virginia Ayres, Michigan State University
Wednesday, January 16, 2008, 2:30 pm, EE 317

Catalyst-free vapor-solid nanowire growth, a newly described method for 
the production of nanowires compatible with a wide variety of 
semiconductor materials, has been used to produce novel multiphase 
zinc-blende/wurtzite gallium nitride nanowires.  Orientation 
relation-ships within the multiphase nanowire were observed using 
high-resolution transmission electron microscopy of cross-sections 
created with focused ion beam techniques.  A totally coherent interface 
be-tween the zinc blende and wurtzite phases, which is sustained over 
the entire length of the nanowire, is identified and discussed.  
Multiphase nanowire growth occurs at specific nanoscale nucleation sites 
on platelets of gallium nitride.  Furnace growth temperature has been 
shown to exert a strong influence on nucleation site formation.  The 
types of nanowires that form and the corresponding nanowire nucleation 
sites over the furnace growth temperature range 850-1000°C are 
discussed.  Multiphase nanowires may have novel properties that augment 
and may be superior to single-phase nanowires in device applications. 
The electronic performance of the new multiphase nanowires in a NanoFET 
configuration is investigated using 2-point and 4-point probe 
current-voltage characterizations. The current-voltage characterizations 
were carried in a special nano-probing system, in which oxide sharpened 
~30 nm radius tungsten nanoprobes were coupled to directly a nanowire 
while the experiments were directly visualized using a scanning electron 
microscope.  All measurements showed high current densities.  Evidence 
for single-phase current transport within the multiphase nanowire 
structure is discussed.  Novel multiphase gallium nitride nanowires and 
nano-circuits may provide unique flexibility for photon and carrier 
confinement.    

*with collaborators: B.W. Jacobs, K. McElroy, M.A. Crimp, Michigan State 
University; J.B. Halpern, and M-Q. He, Howard University; H.C. Shaw, 
NASA Goddard Space Flight Center; M.P. Petkov, NASA Jet Propulsion 
Laboratory.

BIO

Virginia M. Ayres is an Associate Professor in the Department of 
Electrical & Computer Engineering, and heads the Electronic and 
Biological Nano-structures Laboratory (http://www.egr.msu.edu/ebnl) at 
Michigan State University.  Her research interests include the reduced 
dimensionality-based electronic properties of nanotubes and nanowires.  
Dr. Ayres earned her Ph.D. and M.S. in Physics from Purdue University, 
and her B.A. in Physics and Biophysics from the Johns Hopkins 
University.  She is the recipient of two NASA Faculty Fellowship Awards 
and of two international awards from the Japan Society for Promotion of 
Science and from Tokyo Institute of Technology for research and 
education in Japan.  In 2006, she was honored with an Outstanding 
Alumnus Award from the Department of Physics at Purdue University.

-- 

Alicia Goodman
Administrative Assistant
Network for Computational Nanotechnology
Purdue University
Birck Nanotechnology Center
1205 West State Street
West Lafayette, IN  47907
Phone:  765-494-7715
Fax:  765-494-0811
email:  goodman at purdue.edu
website:  www.nanoHUB.org

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