Bifunctional ITO layer with a high resolution, surface nano-pattern for alignment and switching of LCs in device applications

We describe a novel method for liquid crystal (LC) alignment using nano-patterns of electrically conductive indium–tin oxide (ITO) layers with high resolution (ca< 20 nm) and high aspect ratio (ca 10), fabricated based on the secondary sputtering phenomenon. The ITO pattern developed in this manner not only provides high anchoring energy comparable to that of rubbed polyimides, but also maintains its low resistivity as an electrode. As a result, the patterned ITO can function as an electrode and alignment layer at the same time, which facilitates successful fabrication of bifunctional conductive alignment layer for LC devices. The LC cells fabricated using patterned ITO substrates show highly stable alignment of LCs over large area and good electro-optical responses. Moreover, systematic approach made by the precise control of pattern dimensions allows us to estimate a critical anchoring energy required for an effective LC alignment based on Berreman's theory. Hee-Tae Jung, Shin-Woong Kang and co-workers have devised an efficient way to prepare liquid-crystal devices. These devices comprise a layer of liquid crystals – molecules that flow as in a liquid state yet can be aligned over large areas in a crystalline manner – sandwiched between two electrodes. Controlling the orientation of the liquid crystals can be used to modulate light, but this is usually achieved through additional components or processing steps. Relying on a lithographic technique, the researchers have now used ion bombardment and a mould material to create stripes on the surface of an electrically conductive indium tin oxide surface. The resulting material is bifunctional, serving as both an electrode and a way to control the alignment of the liquid crystals over large domains. Devices constructed using indium tin oxide patterned in this way have shown good electro-optical properties, making this technique promising for practical applications. We describe a novel method for liquid crystal (LC) alignment using nano-patterns of electrically conductive indium–tin oxide (ITO) layers with high resolution (ca<20 nm) and high aspect ratio (ca 8), fabricated based on the secondary sputtering phenomenon. The ITO pattern developed in this manner can function as an electrode and alignment layer at the same time, which facilitates successful fabrication of bifunctional conductive alignment layer for LC devices.