  In spite of their enormous applications as alternative energy storage devices
and lubricants, room temperature ionic liquids (ILs) still pose many challenges
from a pure scientific view point. We develop an IL microscopic theory in terms
of ionic clusters, which describes the IL behavior close to charged interfaces.
The full structure factor of finite-size clusters is considered and allows us
to retain fine and essential details of the system as a whole. Beside the
reduction in the screening, it is shown that ionic clusters cause the charge
density to oscillate near charged boundaries, with alternating ion-size thick
layers, in agreement with experiments. We distinguish between short-range
oscillations that persist for a few ionic layers close to the boundary, as
opposed to long-range damped oscillations that hold throughout the bulk. The
former can be captured by finite-size ion pairs, while the latter is associated
with larger clusters with pronounced quadrupole (or higher) moment. The
long-wavelength limit of our theory recovers the well-known
Bazant-Storey-Kornyshev (BSK) equation in the linear regime, and elucidates the
microscopic origin of the BSK phenomenological parameters.
