Liquid crystal alignment properties of inorganic SiO₂layers prepared by reactive sputtering in nitrogen-argon mixtures

According to the advent of ubiquitous world, the requirement for the mobile information devices with high display quality and compact device size is surprisingly increased. Among the diverse candidates for this mobile display system for mobile devices, Liquid Crystal on Silicon (LCoS) is the most competitive device due to the high aperture ratio and simple fabrication process. The inorganic liquid crystal (LC) alignment layers are widely used for LCoS devices because of the thermal and photochemical stability. In this work, the reactive sputtering was selected for the preparation method of inorganic LC alignment layers. The nitrogen (N₂) gas had the effect on the deposition process of SiO₂and the surface morphology of SiO₂thin layers were affected by the N₂mixing ratio of sputtering gas. In addition, the LC alignment properties on SiO₂thin layer were also closely related with the N₂mixing ratio and other sputtering conditions. In the case of high RF power of reactive sputtering, the N₂mixing ratio has little effect on the LC alignment on SiO₂thin layers. However, in the case of low RF power of reactive sputtering, the LC alignment properties were enfeebled by increasing the N₂mixing ratio. This result might be attributed to the change of the surface morphology of inorganic SiO₂thin layers.