AVS 52nd International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS+BI-TuM

Paper AS+BI-TuM4
Ion Beam Alignment of Nematic Liquid Crystal on PPV-layer

Tuesday, November 1, 2005, 9:20 am, Room 206

Session: Surface Characterization of Organic and Biological Systems
Presenter: S. Pylypenko, The University of New Mexico
Authors: S. Pylypenko, The University of New Mexico
K. Artyushkova, The University of New Mexico
J.E. Fulghum, The University of New Mexico
O. Buluy, Institute of Physics of National Academy of Sciences, Ukraine
T. Prokopenko, Institute of Physics of National Academy of Sciences, Ukraine
Y. Reznikov, Institute of Physics of National Academy of Sciences, Ukraine
Correspondent: Click to Email
The development of LCD technologies requires homogeneous alignment of liquid crystals (LCs). The traditional rubbing procedure, consisting of unidirectional brushing of the aligning substrates, is quite reliable but has some drawbacks, including the production of electrostatic charges and dust during the rubbing. Ion and plasma-beam alignment are among the more promising candidates to replace the rubbing procedure. Ion beam alignment is based on an angularly selective destruction and rearrangement of the surface material as a result of ion bombardment, creating orientational order on the initially isotropic surface. Here we report on effective alignment of LCs on an ion-bombarded PPV layer. Glass substrates covered with a thin layer of PPV were irradiated using 2KeV Ar@super +@ ions for varying times. The irradiated substrates were used to assemble planar cells, and the gap was filled with nematic LC 5CB. The measured value of the anchoring energy of ~ 3 10@super -3@ erg cm-2 appeared to be one to two orders of magnitude less than the typical value produced by plasma/ion-alignment. We found enhancement of the stability of the PPV layer in the irradiated area. The strong interaction of 5CB molecules with the PPV surface caused dissolution of the PPV by the LC, and the PPV-layer was not affected by LC in the irradiated region. Three-dimensional characterization of the polymer by X-ray Photoelectron spectroscopy (XPS), Angle Resolved XPS (ARXPS), and Confocal Microscopy (CM) utilizing multivariate analysis (MVA) techniques were carried out to study the mechanism of PPV alignment after ion-beam bombardment. Our results demonstrate that ion-beam treatment provides uniform alignment of liquid crystals characterized by a weak anchoring.