A CU Boulder research team has measured heat passing through glass narrowed to a thread one atom wide. The finding differs from the behavior of ordinary glass, which is known as a poor conductor of heat, the university reported.
The team’s paper, published in Nature Nanotechnology, found that heat traveled through the tiny glass contact in distinct steps. Each step was equal to 40% of the maximum heat a single channel can carry under quantum physics, according to CU Boulder.
The university said it was the first observation of this stepped, or quantized, heat flow carried by atomic vibrations. Study co-author Guilherme de Vilhena, a researcher at the Materials Science Institute of Madrid, said the thread allowed heat through with an efficiency the researchers had not previously seen in an insulator.
The arrangement of atoms helps explain the difference. CU Boulder said the irregular structure of ordinary glass scatters the vibrations that transport heat. In an atom-wide thread, the university said, the vibrations can pass through because there is no room for that disorder.
To make the measurement, the team used a scanning thermal probe microscope. Its glass tip and built-in thermometer measure heat flow where materials meet at the atomic scale. Longji Cui, an assistant professor in CU Boulder’s mechanical engineering department, compared the instrument to a tiny fingertip that can sense temperature and heat flow.
The researchers brought two pieces of glass into contact, then gradually separated them while observing the connection with the microscope. As the pieces moved apart, the glass between them narrowed to a single-atom-wide thread and eventually broke.
Cui said better knowledge of heat flow at the nanoscale is important for managing heat inside small electronic devices. Silicon dioxide, a form of glass, is already used as an insulating layer throughout computer chips, according to the university.
CU Boulder described the findings as potentially useful for designing smaller electronics in the future. Cui also said the microscope could help investigate energy efficiency and reliability in nanoscale electronic devices, including devices made with semiconductors.
Cui said similar behavior might occur in other materials. The university said the microscope can help researchers study atomic-scale heat transport in metals and insulators. Researchers from the Autonomous University of Madrid and the Materials Science Institute of Madrid also participated, and the U.S. National Science Foundation supported the research.
