Pull-in instability of multi-phase nanocrystalline silicon beams under distributed electrostatic force
Abstract
The effects of the material structure on the pull-in instability of nano-actuated beams
made of nanocrystalline silicon (Nc–Si) and subjected to a distributed electrostatic force
are investigated. Nc–Si is represented as a multi-phase material composed of nano-sized
grains, nano voids, and an amorphous-like interface to consider the effects of the interface,
grain size, porosity, and the inhomogeneities surface energies on the elastic properties of
the composite material. To this end, a size-dependent micromechanical model is developed
for multi-phase materials considering the inhomogeneities surface energy effects. An
atomic lattice model is also proposed to estimate the elastic modulus of the interface of
NcMs. Due to the intensive decrease in the beam’s size, the effects of the grain rotations
on the beam strain energy and hence on its rigidity are captured and represented using
the modified couple stress theory. Considering all these effects and using Euler–Bernoulli
beam theory, the governing equation is derived. A finite difference-based solution is used
to determine the pull-in voltage of the actuated beams. A parametric study is then performed
to reveal the effects of the porosity, interface, surface energy, and grain rotations
on the pull-in instability behavior of actuated nano-beams.