  When applying a voltage bias across a thin nanopore, localized Joule heating
can lead to single bubble nucleation, offering a unique platform for studying
nanoscale bubble behavior, which is still poorly understood. Accordingly, we
investigate bubble nucleation and collapse inside solid-state nanopores filled
with electrolyte solutions and find that there exists a clear correlation
between homo/heterogeneous bubble nucleation and the pore diameter. As the pore
diameter is increased from 280 nm to 525 nm, the nucleation regime transitions
from predominantly periodic homogeneous nucleation to a non-periodic mixture of
homogeneous and heterogeneous nucleation. A transition barrier between the
homogeneous and heterogeneous nucleation regimes is defined by considering the
relative free-energy costs of cluster formation. A thermodynamic model
considering the transition barrier and contact-line pinning on curved surfaces
is constructed, which determines the possibility of heterogeneous nucleation.
It is shown that the experimental bubble generation behavior is closely
captured by our thermodynamic analysis, providing important information for
controlling the periodic homogeneous nucleation of bubbles in nanopores.
