A research team supported by the Kavli Institute at Cornell for Nanoscale Science has released the first known direct measurements of hot electrons cooling down in graphene, in an effort to answer questions about the heating and cooling behavior of electrons. The findings are published online in the journal Nature Physics.
When electrons travel through graphene, a quantum lattice vibration known as a phonon is created. In order to return the system to its equilibrium state, the difference in energy the electron emits must equal the amount gained by the phonon. This movement of electrons is central to the understanding of how electronic devices function.
Led by Paul McEuen, director of the Kavli Institute, the team constructed an experiment to test the theory that electrons in graphene experience “supercollisions” with defects in the crystal lattice. These collisions speed up the cooling process by transferring the momentum of the electrons to the defects.
Using short laser pulses, the team observed the temperature of the graphene as it heated and cooled at a p-n junction, the interface at which electrons travel between two semiconductors.
According to McEuen, the results obtained by the research team provide further insights into “the fundamental nature of graphene,” so that in the future it can be used in “anything from photodetectors to non-silicon transistors.”
Graphene already shows promise for next-generation electronics due to its almost-perfect conductivity, transparency and tensile strength; the addition of a faster cooling process is one more asset.
