Ballistic Thermal Conductance of a Lab-in-a-TEM Made Si Nanojunction

The thermal conductance of a single silicon nanojunction
was measured
based on a Lab-in-a-TEM (microelectromechanical
systems in a transmission electron microscope) technique and was found
to be at least 2 orders of magnitude larger than the ones of long
nanowires in the 380–460 K temperature range. The predominance
of ballistic phonon transport appears as the best hypothesis to retrieve
quantitative predictions despite the geometrical irregularity of the
junction. The measurement is based on a MEMS structure including an
electrostatic actuator that allows producing nanojunctions with the
accuracy based on the resolution of a transmission electron microscope.
The thermal conductance is measured by two integrated resistors that
are simultaneously heating and measuring the local temperatures at
the nearest of the nanojunction. The considerable thermal conductance
of short nanojunctions constitutes a new key element in the design
of nanosystems and in the understanding of the damaging of mechanical
micronanocontacts. This conducting behavior is also paving the way
for the development of nanoscale cooling devices as well as of the
recent phononic information technology.