Good Vibrations Probe Innards of Molecular Electronic Junctions

Mar 05, 2008
Good Vibrations Probe Innards of Molecular Electronic Junctions
NIST researchers determined that the organic molecules in the middle of this simple silicon-based molecular “sandwich” pass electric current through these junctions by carefully measuring the minute changes in molecular vibrations. Credit: NIST

Using an unusual spectroscopic technique, researchers at the National Institute of Standards and Technology have provided the most convincing evidence yet that current is flowing through a simple silicon-based molecular “sandwich,” which is the most basic structure of molecular electronics. The work is an important step toward realizing the dream of organic molecule-based electronics that could enable much denser, cheaper computer memories and other replacements of traditional electronic devices.

“The ultimate in miniaturization is the molecule,” explains NIST’s Curt Richter. “The hope is that a single molecule will one day be able to act as an electrical component such as a diode or a resistor with the ultimate goal being shrinking computer chips.”

For the past few years, scientists have been building and testing structures made of a hybrid of traditional silicon-based components and more futuristic molecule-based components. The typical junction is a sandwich of a metallic contact layer, a layer of organic compound just a single molecule thick arranged like bristles on a brush, and a substrate of silicon. Richter says that while the electric current seems to pass through the molecules, the current could be finding a way around it or the molecules could have been damaged in fabrication. Scientists want to know what is really happening inside this “black box.”

NIST researchers tried a little-used technique called inelastic electron tunneling spectroscopy (IETS) that measures the vibrations of the molecules inside the junction. “Each molecule has its own vibrational fingerprint,” says Wenyong Wang, adding “IETS acts as our eyes to see what is inside the black box.” An earlier paper by Wang and his colleagues at Yale University set IETS as a standard technique to prove that molecules remain intact in metal-based molecular electronic devices.

Colleagues at Purdue University provided three types of silicon-molecule-metal junctions that are a few micrometers large. The small molecules researchers used were octadecane, nitrobenzene and diethylaminobenzene.

Each silicon-molecule-metal device was cooled to cryogenic temperatures. Wang carefully measured the minute changes in the current passing through the junctions, and these current changes were then related to specific molecular vibrations. Thus, the researchers verified the existence of the molecules and that the electric current passed through them.

NIST physicists plan to continue research into silicon-molecule-metal junctions. “Once we understand the physics of the devices, we can begin to assess how viable the technology is and also determine which molecules may supply the best chance for a technological breakthrough,” says Richter.

Citation: W. Wang, A. Scott, N. Gergel-Hackett, C.A. Hacker, D.B. Janes and C.A. Richter. Probing molecules in integrated silicon-molecule-metal junctions by inelastic tunneling spectroscopy. ACS Nano Letters, 8, 478 (2008).

Source: NIST

Explore further: Toward making lithium-sulfur batteries a commercial reality for a bigger energy punch

add to favorites email to friend print save as pdf

Related Stories

Tracing water channels in cell surface receptors

Sep 09, 2014

G protein-coupled receptors (GPCRs) are the largest class of cell surface receptors in our cells, involved in signal transmission across the cell membrane. One of the biggest questions is how a signal recognized at the extracellular ...

Doped graphene nanoribbons with potential

Sep 08, 2014

Graphene is a semiconductor when prepared as an ultra-narrow ribbon – although the material is actually a conductive material. Researchers from Empa and the Max Planck Institute for Polymer Research have ...

Recommended for you

A nanosized hydrogen generator

3 hours ago

(Phys.org) —Researchers at the US Department of Energy's (DOE) Argonne National Laboratory have created a small scale "hydrogen generator" that uses light and a two-dimensional graphene platform to boost ...

For electronics beyond silicon, a new contender emerges

Sep 16, 2014

Silicon has few serious competitors as the material of choice in the electronics industry. Yet transistors, the switchable valves that control the flow of electrons in a circuit, cannot simply keep shrinking ...

Making quantum dots glow brighter

Sep 16, 2014

Researchers from the University of Alabama in Huntsville and the University of Oklahoma have found a new way to control the properties of quantum dots, those tiny chunks of semiconductor material that glow ...

The future face of molecular electronics

Sep 16, 2014

The emerging field of molecular electronics could take our definition of portable to the next level, enabling the construction of tiny circuits from molecular components. In these highly efficient devices, ...

User comments : 0