For unidirectional uniform alignment of liquid crystals (LCs), alignment layer materials (ALMS) such as oblique evaporated SiO, rubbed polyimide (PI), UV-irradiated photopolymer, and IB-irradiated diamond like carbon (DLC) have been investigated. To overcome the demerits of the mechanical rubbing process, we used ion beam (IB)-treated carbon incorporated hydrogenated amorphous silicon oxide (a-S10(X)C(Y):H) for the planar alignment. In this paper, we suggest a-SiOXCY:H treated by IB irradiation increases pretilt angle. As the amount of incorporated carbon is increased, pretilt angle is increased because of the change of surface energy. In addition, IB conditions such as IB irradiation time, angle, and energy affect the pretilt angle. (C) 2007 Elsevier B.V. All rights reserved.