Hybrid Metal-Semiconductor Nanoparticles
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Date: 07-31-2006
Start Time:
11:00am
End Time: 12:00pm
Speaker: Uri Banin
From:
University of Jerusalem, Israel
Location: Interschool Lab, 7th floor, Schapiro/CEPSR
Hosted by:
Center for Integrated Science
Abstract:
An important frontier in nanocrystal synthesis is the growth of
composites of different materials in the same nanostructure as means of
increasing functionality. One particularly interesting combination of
materials is that of a metal and semiconductor in the same nanoparticle
where metal tips can provide anchor points for electrical connections
and for self assembly. We developed the growth of metal (Au) tips on
the apexes of semiconductor (CdSe) rods, forming 'nano-dumbbells'
(NDB's), via a simple chemical reaction . From the viewpoint of
self-assembly they are equivalent to bi-functional molecules such as
the di-thiols manifesting two sided chemical connectivity and the use
of the tips for assembly is demonstrated. We also found that by
increasing the concentration of gold in the reaction, rods with a metal
tip on one side are formed . This process occurs by a unique ripening
process as substantiated by experimental work and model calculations.
The process leads to a transition from two to one sided growth. Such
systems manifest a unique model for a metal-semiconductor nanoscale
junction. A fundamental and intriguing problem associated with such
systems is the mechanical and electronic properties of the metal-SC
nanojunctions. The electronic properties of metal-semiconductor
nanojunctions were investigated by scanning tunneling spectroscopy of
the gold-tipped CdSe rods and by electrostatic force microscopy. In STS
sub-gap states at the metal-semiconductor interface were observed ,
while in EFM we see evidence for charge separation at the
metal-semiconductor interface.
1. T Mokari, E Rothenberg, I Popov, U Banin, Science 304, 1787 (2004)
2. T Mokari, CG Sztrum, A Salant, E Rabani and U Banin, Nature Materials 4, 855 (2005)
3. D Steiner, T Mokari, U Banin, O Millo, Physical Review Letters 95, 056805 (2005)