  We report on the modeling of the formation of a cavity at the surface of
crystals confined by a flat wall during growth in solution. Using a continuum
thin film model, we discuss two phenomena that could be observed when
decreasing the thickness of the liquid film between the crystal and the wall
down to the nanoscale. First, in the presence of an attractive van der Waals
contribution to the disjoining pressure, the formation of the cavity becomes
sub-critical, i.e., discontinuous. In addition, there is a minimum
supersaturation required to form a cavity. Second, when the thickness of the
liquid film between the crystal and the substrate reaches the nanoscale,
viscosity becomes relevant and hinders the formation of the cavity. We
demonstrate that there is a critical value of the viscosity above which no
cavity will form. The critical viscosity increases as the square of the
thickness of the liquid film. A quantitative discussion of model materials such
as Calcite, Sodium Chlorate, Glucose and Sucrose is provided.
