Topography of Thin Teflon Layers and Induced Orientation of Nematic Liquid Crystals

• Published in: Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals Vol. 333; no. 1; pp. 181 - 191
• Main Authors: Cuminal, Marie-Pierre, Touhari, Françoise, Brunet, Monique, Cohen-Solal, Gerard
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group 01.08.1999; Gordon and Breach
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Liquid crystals; Organic polymers; Orientational order of liquid crystals; electric and magnetic field effects on order; PACS. 61.30 -v- Liquid crystals; PACS. 68.55. -a - Thin film structure and morphology; PACS.42.79.Yd - Optical elements, devices, and systems; Physicochemistry of polymers; Physics; Properties and characterization; Structure of solids and liquids; crystallography; Surface properties; Alignment; Pressure effect; Molecular orientation; Tetrafluoroethylene polymer; Morphology; Temperature effect; Fabrication structure relation; Experimental study; Liquid crystals; Nematic crystals; Thin film; Deposition process
• ISSN: 1058-725X
• DOI: 10.1080/10587259908026004

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. Les couches minces en PTFE sont utilisées depuis peu comme couches d′orientation pour aligner les molécules de cristal liquide. Dans cette contribution, nous étudions d′une part l′influence des paramètres de dépôt (pression, vitesse et température) sur la morphologie des couches observées en utilisant les techniques de microscopie optique et de microscopie à force atomique. De plus, nous avons mesuré l′angle de pretilt induit sur les nématiques par ces films. Cet angle est faible, de l′ordre de 0.3°. Bien que la topographie des couches déposées varie lorsque les paramètres de dépôt changent, les textures du nématique ne changent pas.