Solid State Phenomena Vols. 181-182

Abstract: An optical tunable filter with variable bandwidth has been demonstrated using two cholesteric liquid crystals. The incident light was first reflected by the first cholesteric liquid crystal and then by the second one. By rotating the two cholesteric liquid crystals simultaneously, the central wavelength can be tuned. By fixing one of the cholesteric liquid crystals and rotating the other one, the bandwidth of the tunable filter can be varied. The central wavelength of the tunable optical filter can be tuned from 513.4 nm to 576.8 nm and the bandwidth is varied from 10 nm to 80 nm. This property will allow it to be widely used in many fields, including optical communications and multispectral and hyperspectral imaging systems.

Abstract: In this paper, the liquid crystal grating-based 3D display will be introduced, and emphasis on the ‘movable’ characteristic of the LC grating. To make LC grating tunable, the required lighted LC grating pixels would be controlled via programming in order to solve the following questions: the pixels loss or the single viewing point.

Abstract: The performance of a reflective chiral-homeotropic (R-CH) liquid crystal (LC) is simulated by the dynamic parameter space method. The normally black reflective chiral-homeotropic display shows weak color dispersion, high contrast ratio, and fast response time.

Abstract: On the basis of the photoluminescence spectra, a spectrophotometric methodology is developed to determine the color coordinates of luminescent materials such as the red light-emitting porous silicon film, the green light-emitting aluminate-based phosphor and the blue light-emitting liquid crystal.

Abstract: Liquid crystal polymers are the low cost, flexible structured and low weight substrate materials for making antennas. Liquid crystal polymers are excellent dielectric materials having good electrical, mechanical properties which suites in the application of microstrip patch antennas. In this paper liquid crystal polymer with dielectric constant 3.16 is used as substrate material for planar dipole antenna designed to operate at 2.4 GHz. Ansoft-HFSS software is used to simulate the proposed model and obtained the return loss, input impedance, 3D-gain, 2D-gain total, radiation patterns in E and H planes, E-field and H-field distribution results.

Abstract: Liquid crystal, as a condensed matter, is a phase state between crystal and isotropic liquid. On the one hand, it has mobility and continuity as a liquid, and on the other hand, it has arranging ordering as a crystal, then it has many unique properties. Because the factors, such as heat, electric field, magnetic field, pressure, and so on, will easily influence the arranging of liquid crystal molecular, so once it is excited externally, its optical properties will be changed. At present, most research on the theory and application of liquid crystal mainly focus on the display. Thermo-optic effect is defined as the phenomenon that the optical properties of liquid crystal change with the changing of temperature. At the phase transition point, the thermo-optic effect of liquid crystal is very obvious. In this paper, non-electric readout infrared thermal imaging detection technology based on the optical rotation property of the cholesteric liquid crystals is mainly researched. Through the research, the cholesteric liquid crystals’ light curves, gray value curves and CCD image were obtained under different temperatures; it proved that using the optical rotation property of cholesteric liquid crystals to achieve the infrared imaging of hot objects is possible.

Abstract: Liquid crystal variable retarders (LCVRs) are starting to be widely used in optical systems because of their capacity to provide a controlled variable optical retardation – an important technical parameter for LCVRs. In this paper, using polarization condition change of polarized light, a set of measurement systems is built. Through the measurement of the relative value of luminous intensity instead of the absolute value which can be easy affected by ambient light and the illuminant instability, it can comparative accurately acquire electrically controlled phase retardation of LCVRs. With the light source of He-Ne laser with the wave 632.8 nm, at temperature 25 °C, a standard quarter-wave plate has been measured, with the relative error less than 1 %.

Abstract: We achieves switchable between autostereoscopic 2-view 3-D and 2-D display on a 10.1-inch LCD panel using GRIN LC lens with a 20 um cell gap and 14 volt driving voltage. Simulation results such as refraction distribution and 3-D crosstalk verify the performance of this LC lens for autostereoscopic 2-D/3-D switchable display.

Abstract: Nonvolatile memory (NVM) devices with nitride-nitride-oxynitride (NNO) stack structure using Si-rich silicon nitride (SiN_x) as charge trapping layer on glass substrate were fabricated. Amorphous silicon clusters existing in the Si-rich SiN_x layer enhance the charge storage capacity of the devices. Low temperature poly-silicon (LTPS) technology, plasma-assisted oxidation/nitridation method to form a uniform ultra-thin tunneling layer, and an optimal Si-rich SiN_x charge trapping layer were used to fabricate NNO NVM devices with different tunneling thickness 2.3, 2.6 and 2.9 nm. The increase memory window, lower voltage operation but little scarifying in retention characteristics of nitride trap NVM devices had been accomplished by reducing the tunnel oxide thickness. The fabricated NVM devices with 2.9 nm tunneling thickness shows excellent electrical properties, such as a low threshold voltage, a high ON/OFF current ratio, a low operating voltage of less than ±9 V and a large memory window of 2.7 V, which remained greater than 72% over a period of 10 years.

Abstract: Based on nonequilibrium Green’s function and first-principles calculation, we investigate the transport properties of the molecule device with a donor-acceptor molecular complex sandwiched between two electrodes. Numerical results show that a negative differential resistance under applied bias can be observed. The mechanism of negative differential resistance is mainly induced by the orbital match of molecule and electrodes as well as intermolecular charge transfer.