CPM Seminar
Exploiting nanoscale structure:
from tuning single
electron effects to driving insulator-metal transitions
Al-Amin Dhirani
University of Toronto
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.
Thursday, April 10th 2003, 15:30
Ernest Rutherford Physics Building, R.E Bell Conference Room (room 103)
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