We investigated liquid crystal alignment on a-SiQ(x) thin films by means of X-ray diffraction and X-ray photoemission spectroscopy as we varied the deposition temperature and the target-to-substrate distance. We found that liquid crystal molecules can be aligned vertically on a-SiOx film when the stoichiometry parameter x of a-SiOx is smaller than 1.56, but they can be aligned homogeneously when x is larger than 1.56. We also found that whether liquid crystals can be aligned vertically or homogeneously on a-SiOx film can be predicted simply by measuring the change in optical transmittance by deposition of a-SiOx thin film layers. (c) 2006 Elsevier B.V. All rights reserved.