Hysteresis-free, energy efficient twisted nematic liquid crystal systems based on IB-irradiated gallium-doped tin oxide films

Abstract: We successfully demonstrated the high performance of liquid crystal (LC) devices without capacitance hysteresis using ion-beam (IB)-irradiated GaSnO in solution. This method is widely used for obtaining inorganic films, although it yields poor crystallinity, owing to its cost effectiveness and high flexibility in combining materials. Atomic force microscopy and X-ray photoelectron spectroscopy analyses determined that IB irradiation on the films had an effect, which enabled the elucidation of the mechanism for LC alignment. Strong IB irradiation on GaSnO induced the formation of spherical particles on the films and rearrangement of the chemical bonds (linkage of Ga–Sn–O and gradually oxidized films), which could preserve the anisotropic characteristics to unidirectionally align LC molecules on the surface. Because rough surfaces effectively increase the electric field, the strongly restructured GaSnO surface led to a decrease in threshold voltages. Moreover, strong IB irradiation effectively released volume charges when the states of LC molecules were switched “on” and “off”, which is attributed to a reduction in oxygen bonding derived from hydroxyl groups responsible for capturing neutral electrons. Therefore, an IB-irradiated GaSnO film is appropriate as an alternative alignment layer for advanced, energy efficient, hysteresis-free LC display devices. Graphical Abstract: We successfully demonstrated the high performance of liquid crystal (LC) devices without capacitance hysteresis using ion-beam (IB)-irradiated GaSnO in solution. This method is widely used for obtaining inorganic films, although it yields poor crystallinity, owing to its cost effectiveness and high flexibility in combining materials. (a) Schematic of the IB irradiation of the solution-derived GaSnO film. (b) Alignment state of the LCs as a function of IB intensity. (c) Transmittance graph using the crystal rotation method to calculate the pretilt angle. (d) Transmittance as a function of voltage of the twisted nematic (TN) cells fabricated from IB-irradiated GaSnO at different intensities compared to the rubbed PI method (e) Capacitance of the TN cells fabricated from IB-irradiated GaSnO at 2200 eV, which exhibited hysteresis-free characteristic of TN cells. Because rough surfaces effectively increase the electric field, the strongly restructured GaSnO surface led to a decrease in threshold voltages. Moreover, strong IB irradiation effectively released volume charges when the states of LC molecules were switched “on” and “off”, which is attributed to a reduction in oxygen bonding derived from hydroxyl groups responsible for capturing neutral electrons. Therefore, an IB-irradiated GaSnO film is appropriate as an alternative alignment layer for advanced, energy efficient, hysteresis-free LC display devices.[Figure not available: see fulltext.]