Depth of Interaction of Nematic Liquid Crystals with Crystalline Substrates

By analysing the anchorings of nematic liquid crystals observed on cleaved muscovite and phlogopite micas and on vicinal silicon surfaces, we show that the surface interacting with the nematic liquid crystals and contributing to orient them is not the infinitely thin top part of these substrates. We find that this surface is a three-dimensional layer whose thickness is approximately 14 Å for muscovite mica and less than 5 Å for phlogopite mica. In the case of silicon surfaces, the experimental results allow only to give a lower value of this thickness, which is 6 Å.