  We demonstrate that the surface of the honeycomb lattice iridate
Na$_2$IrO$_3$ is extremely tunable by plasma etching. We have succeeded in
turning the surface of Na$_2$IrO$_3$ metallic by Ar plasma etching which leads
to the removal of Na from the surface. The surface structure does not change in
this process as revealed by grazing incidence small angle x-ray scattering
(GISAXS). The sheet resistance $R_s$ can be reduced by several orders of
magnitude by varying the etching duration. Temperature dependent $R_s(T)$ for
the metallic samples show signatures of spin or charge density wave transitions
with abrupt changes in $R_s$. Thermal hysteresis between cooling and warming
measurements across the transition indicates a first order transition. For the
most metallic sample $R_s(T)$ data at low temperatures follow a $T^2$ behaviour
suggesting normal Fermi liquid behaviour.
