You can touch a functioning light bulb and know right away that it's hot. Ouch! But you can't touch a single molecule and get the same feedback.
Rice University researchers say they have the next best thing -- a way to determine the temperature of a molecule or flowing electrons by using Raman spectroscopy combined with an optical antenna.
A new paper from the lab of Douglas Natelson, a Rice professor of physics and astronomy, details a technique that measures the temperature of molecules set between two gold nanowires and heated either by current applied to the wires or laser light. The paper was published this week in the online edition of Nature Nanotechnology.
Natelson, postdoctoral research associate Dan Ward and their colleagues found that while measuring heat at the nanoscale can be much more complicated than taking the temperature of macro objects, it can be done with a level of accuracy that will be of interest to the molecular electronics community or anyone who wants to know how heating and dissipation work at very small scales.
"When you get down to making small electronic devices or tiny junctions, you have to worry about how energy ends up in the form of heat," Natelson said. "In the case of macroscopic objects, like the filament in a light bulb, you can attach a thermocouple -- a thermometer -- and measure it." When light bulbs get hot, they also glow. "If you look at the spectrum of the light coming out, you can figure out how hot it is," he said.
That's an over-simplified version of what Natelson and Ward are doing. One can't see the glow of a molecule. However, the researchers can send in light as a probe and detect the wavelength of the light that molecule is returning when heated. "In Raman scattering, you send in light that interacts with your target. When it comes back, it will either have more energy than you put in, or the same, or less. And we can see that and figure out the effective
|Contact: David Ruth|