Topography of thin teflon layers and induced orientation of nematic liquid crystals

It has recently been shown that teflon (PTFE) films can be used as orientation layers to align liquid crystal molecules. In this paper we study the influence of the deposition parameters (pressure, speed and temperature) on the layer morphology given by both optical and atomic force microscopy. In addition, we have measured the surface pretilt angle induced on nematics by these films. It turns out that teflon gives a small pretilt, of the order of 0.3 degrees, at the surface. Although the topography of the deposited layer is seen to vary, the characteristic nematic textures do not vary with a variation of the deposition parameters.