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. NPG Asia Materials (2012) 4, e7; doi:10.1038/am.2012.12; published online 17 February 2012