Tilted smectic layers of a SmC* liquid crystal between homeotropically treated plates

We investigated SmC* films sandwiched between silane coated glass prates and observed formation of textures exhibiting a uniform tilt of the smectic layers with respect to the boundary prates. The layer tilt angle increases from zero to 14 degrees as the sample is cooled from the smectic A phase to room temperature. These films show linear electro-optical effects because the permanent polarization can be aligned so that it has a component parallel to the applied field without changing the layer structure. Our analysis indicates that mainly two effects determine the layer tilt. On the one hand, the surface tension tends to minimise the layer tilt. On the other hand, the surface energy promotes the director to be normal to the boundary plates.