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UCLA-Based Team Builds Tool To Probe Nanoscale Interactions

by Editor1 last modified December 13, 2010 - 11:14

A team of researchers led by Paul Weiss, UCLA’s Fred Kavli Chair in NanoSystems Sciences, has developed a tool aimed to help discern how nanoscale materials might be best used to foster the next-generation of electronics.

UCLA-Based Team Builds Tool To Probe Nanoscale Interactions

UCLA's Paul Weiss leads team developing nanoscale probe for electronics.

For the past 50 years, the electronics industry has tried to keep pace with Moore’s Law, a prediction that transistors in integrated circuits decrease in size by half every two years. While that trend is largely in place since first predicted in 1965, of late researchers have run into obstacles as measuring transistors at the nanoscale has proven problematic.

The device is a dual scanning tunneling and microwave-frequency probe. It is designed to explore how materials at the nanoscale exhibit different properties than at larger scales by studying the properties of nanoscale interactions between single molecules – and the surfaces to which molecules are attached.

“Our probe can generate data on the physical, chemical, and electronic interactions between single molecules and substrates -- the contacts to which they are attached,” said Weiss. “Just as in semiconductor devices, contacts are critical here.”

The team also includes theoretical chemist Mark Ratner from Northwestern University, and synthetic chemist James Tour from Rice University.

The connections between components are a vital element of nanoscale electronics. For molecular devices, polarizability measures the extent to which electrons of the contact interact with those of the single molecule.

Two key aspects of polarizability measurements are
  1. The ability to do the measurement on a surface with sub nanometer resolution, and
  2. The ability to understand and to control molecular switches in both the on and off states.

To measure the polarizability of single molecules Weiss’ team developed a probe capable of simultaneous scanning tunneling microscopy (STM) measurements and microwave difference frequency (MDF) measurements. Using the probe’s MDF capabilities, the team was able to actually locate single molecule switches on substrates, even when the switches were in the off state, a key capability lacking in previous techniques.

Once they located the switches, the team could use the STM to change the state to on or off and to measure the interactions in each state between the single molecule switches and the substrate.

The probe is capable of a wide variety of measurements — including physical, chemical and electronic — it could enable researchers to identify sub molecular structures in complex biomolecules and assemblies, Weiss said.

Weiss also directs UCLA’s California NanoSystems Institute and is also a distinguished professor of chemistry and biochemistry & materials science and engineering.

The team published their findings in the peer-reviewed journal ACS Nano.