nano 2007-12-16 04:27
ACS Nano Picks 04:Observation of negative differential resistance with
[b][size=4] ACS Nano Picks 03:Observation of negative differential resistance with Ni STM tips[/size][/b]
[img]http://www.acsnanotation.org/Portals/0/latha.jpg[/img]
By Prof. Latha Venkataraman
Columbia University
Article Title: [url=http://link.aps.org/abstract/PRL/v99/e146803]Mechanism for Negative Differential Resistance in Molecular Electronics Devices: Local Orbital Symmetry Matching[/url]
Article Citation: [i]Physical Review Letters [/i][b]99[/b], 146803 (2007)
[b]Article Review:[/b]
Negative differential resistance (NDR) in single molecule devices has been seen by many groups over the past decade. Most groups do not see NDR at well-defined bias voltages in scanning tunneling microscopy (STM) measurements; when it is seen, it is usually attributed to the non-uniform local density of states of a particular STM tip used in the experiments. In this work, researchers have probed electronic properties of cobalt phthalocyanine on a gold substrate STM measurements. They observe NDR reproducibly at a well-defined bias voltage when they image the molecules with nickel tips, while they do not observe NDR when imaging with tungsten tips. They attribute these results to the resonant tunneling from the Co dxz(yz) orbitals on the molecule to the Ni dxz(yz) of the tip. This work thus provides a novel mechanism for NDR supporting their experimental results.