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Proceedings Paper

Liquid crystal surface alignments by using films composed of magnetic nanoparticles
Author(s): Ru-Pin Pan; Hsin-Ying Wu; Cho-Fan Hsieh
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Paper Abstract

A method for liquid crystal surface alignment by using a one-step, ion beam sputtering on glass substrates is demonstrated. Pre-coating by polyimide is not necessary. We use a diode-type sputter to treat the glass substrates with Ar ion-beam. The homeotropic alignments for nematic liquid crystals are achieved. The alignments are characterized by using the polarizing optical microscope and the conoscope. To find out the alignment mechanism, the studies by using super conducting quantum interference device and scanning probe microscopy are carried out. The surveyed surface morphology reveals that the films are amorphous and composed of nanoparticles with dimensions around 30 nm. The magnetization anisotropy of the sputtered magnetic films is analyzed. The polar anchoring strengths of the coated films with different thicknesses are measured and compared with their saturation magnetization. We deduce that the homeotropic alignment is achieved due to the orientation of the diamagnetic nematogenic molecules in the magnetic field caused by the γ-Fe2O3 ferrimagnetic thin films. A simple model of alternatively distributed magnetic moments with opposite direction is proposed. The profile of magnetic field strength near the surface is then calculated to compare with the measured alignment strength.

Paper Details

Date Published: 29 January 2008
PDF: 11 pages
Proc. SPIE 6911, Emerging Liquid Crystal Technologies III, 691104 (29 January 2008); doi: 10.1117/12.762985
Show Author Affiliations
Ru-Pin Pan, National Chiao Tung Univ. (Taiwan)
Hsin-Ying Wu, National Chiao Tung Univ. (Taiwan)
Cho-Fan Hsieh, National Chiao Tung Univ. (Taiwan)

Published in SPIE Proceedings Vol. 6911:
Emerging Liquid Crystal Technologies III
Liang-Chy Chien, Editor(s)

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