  Traditional electronic devices are well-known to improve in speed and
energy-efficiency as their dimensions are reduced to the nanoscale. However,
this scaling behavior remains unclear for nonlinear dynamical circuit elements,
such as Mott neuron-like spiking oscillators, which are of interest for
bio-inspired computing. Here we show that shrinking micrometer-sized VO2
oscillators to sub-100 nm effective sizes, achieved using a nanogap cut in a
metallic carbon nanotube (CNT) electrode, does not guarantee faster spiking.
However, an additional heat source such as Joule heating from the CNT, in
combination with small size and heat capacity (defined by the narrow volume of
VO2 whose insulator-metal transition is triggered by the CNT), can increase the
spiking frequency by ~1000x due to an electro-thermal bifurcation in the
nonlinear dynamics. These results demonstrate that nonlinear dynamical switches
operate in a complex phase space which can be controlled by careful
electro-thermal design, offering new tuning parameters for designing future
biomimetic electronics.
