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Condensed Matter Physics Seminar


Exploiting nanoscale structure: from tuning single electron effects to driving insulator-metal transitions

Al-Amin Dhirani
University of Toronto

Time
 
Wed. March 12, 2003     10:30 AM     Stirling 501

Abstract
 

Nanostructure electrical measurements represent a frontier in chemistry and physics. One of the driving forces in this field is the idea that nanoscale control over local conductivities within a material offers a possibility to design rationally its averaged electrical properties. In the first part of this talk, I will present single nanoparticle measurements obtained with a homemade hybrid scanning tunneling - atomic force microscope (STM-AFM). We used the STM-AFM to probe single electron effects generated in a nanoparticle-tunnel junction system, and observed discrete force jumps associated with sudden changes in current characteristics. The measurements confirm a current valving effect that single charges can exhibit at such small scales. Threshold voltages for single electron events were found to be tunable with nanoparticle size as predicted by theory. The second part of my talk describes how information about nanoscale conductivities can be exploited to rationalize conductivities of nanoparticle/molecular linker composites or "artificial solids". For example, by making films of varying thicknesses, we can drive a rapid percolation transition from insulating to metallic composite behaviour. The transition can also be driven by varying molecular linker. The results compare favorably with theory that uses local conductivities as input and point to a significant potential to generate materials with designer properties.

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