Homogeneous liquid crystal alignment on inorganic-organic hybrid silica thin films derived by the sol-gel method

We developed an inorganic-organic hybrid thin film via the sol-gel method for a new liquid crystal alignment layer and investigated the influence of an organic species on the alignment characteristics of the liquid crystals (LCs). A thin film of methyl-doped amorphous silicon oxide (a-SiO _x:CH ₃) was fabricated from the hydrolysis and condensation reaction of the initial precursors of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) at a proper ratio. A low-energy ion beam (IB) treatment gives rise to the homogeneous alignment of LC in an IB condition on a-SiO _x:CH ₃ thin film; however, it is difficult to control the LC alignment on a-SiO _x thin film derived only from TEOS as a precursor. The LC alignment depending on the chemical structure of the silica thin film was investigated and analyzed in terms of the sensitivity of the axis-selective destruction of the chemical bonding on the surface of the thin silica film.