  In this work we have studied the effect of target thickness on relativistic
self-induced transparency (RSIT) and found out that for subwavelength targets
the corresponding threshold target density (beyond which target is opaque to
incident laser pulse of a given intensity) increases. The accelerating
longitudinal electrostatic field created by RSIT from subwavelength target is
used to accelerate the ion bunch from a thin, low density layer behind the main
target to $\sim$ 100 MeV. A suitable scaling law for optimum laser and target
conditions is also deduced. The word `via' in the title signifies the fact that
we are interested in acceleration of ions from the layer placed behind the
target. It is also being observed that as per as energy spectrum is concerned;
an extra low density layer is advantageous than relying on target ions alone.
