  We study the surface substrate inhomogeneity effect on the wetting of a
spin-1/2 Ising ferromagnetic film in an external magnetic field $H$, using
Monte Carlo simulations. It is found the inhomogeneity leads to the formation
of islands of positive spins in each layer. However, depending on the values of
$H$, for a fixed surface magnetic field $H_s$, each layer exhibits three
different phases; totally wet, nonwet and partially wet (PW). In the latter
case, we show the existence of three distinct configurations namely: A
configuration (PWTD) in which the layer is partially wet with a total
disconnection between islands; (PWPD) a configuration in which the layer is
partially wet with a partial disconnection between islands; (PWTC) a
configuration in which the layer is partially wet and the islands are totally
connected. Furthermore, we show that an increase of $H_s$ values breaks the
bonds connecting some islands of the phase (PWTC) which leads to an expansion
of the (PWPD) region. On the other hand, the frequency distribution and the
mean size of island are investigated in the (PWTD) region for fixed values of
temperature $T$, $H_s$ and $H$. Moreover, we show the existence of 3D-islands
resulting from the formation of islands in each layer.

Materials Science