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Immersion transmission ellipsometry (ITE) for the determination of orientation gradients in photoalignment layers

: Jung, C.C.; Stumpe, J.


Applied Physics. B 116 (2014), No.3, pp.533-539
ISSN: 0340-3793
ISSN: 0721-7269
ISSN: 0946-2171
ISSN: 1432-0649
Journal Article
Fraunhofer IAP ()

The capability of the method of immersion transmission ellipsometry (ITE) (Jung et al. Int Patent WO, 2004/109260) to not only determine three-dimensional refractive indices in anisotropic thin films (which was already possible in the past), but even their gradients along the z-direction (perpendicular to the film plane) is investigated in this paper. It is shown that the determination of orientation gradients in deep-sub-mu m films becomes possible by applying ITE in combination with reflection ellipsometry. The technique is supplemented by atomic force microscopy for measuring the film thickness. For a photo-oriented thin film, no gradient was found, as expected. For a photo-oriented film, which was subsequently annealed in a nematic liquid crystalline phase, an order was found similar to the one applied in vertically aligned nematic displays, with a tilt angle varying along the z-direction. For fresh films, gradients were only detected for the refractive index perpendicular to the film plane, as expected.