Light extraction efficiency of a conventional organic light emitting diode (OLED) remains limited to approximately 20% as most of the emission is trapped in the waveguide and glass modes. An etchless simple method was developed to fabricate two-dimensional nanostructures on glass substrate directly by using ultraviolet (UV) curable polymer resin and UV nanoimprint lithography in order to improve output coupling efficiency of OLEDs. The enhancement of the light extraction was predicted by the three-dimensional finite difference time domain method. OLEDs integrated on nanoimprinted substrates enhanced electroluminance intensity by up to 50% compared to the conventional device.
We report on the development of a metrological multiaxis nanopositioning device, which is operated by the piezo-based inertial method, as a sample stage for scanning probe microscopy. It has long moving range, unlimited in principle, and nanometer ͑microradian͒ resolution. Two operation methods, inertial sliding and inertial walking, can be applied to the stage and the inertial operating method can make the stage have a simple and compact structure. By the structure and operation method high positioning stability can be obtained which is an important requirement for scanning probe microscopy. For a metrological nanopositioner, a three axes laser interferometric sensing scheme is adopted for planar motion and a 15 channel high voltage amplifier is designed and computer based digital-to-analog conversion is adopted. Therefore the nanopositioner can be feedback controlled with many choices of voltage wave forms and control methods. Design of the nanopositioner and piezo-driver and experimental results are presented. The device provides step sizes of 0.016-10 m at frequency up to about 7 kHz. The rotational range is limited by the interferometer alignment, 0.2°, and the step size is 0.17-103 arcsec.
Patterning flexible substrates in nano scale is an important and challenging issue in the fabrication of next-generation devices based on a non-silicon substrate. Step and Flash imprint lithography (S-FIL) which is a room temperature and low pressure process offers several important advantages, such as the use of a smaller and therefore cheaper stamp or the possibility of the overlay imprinting, as a transparent stamp is utilized. However, it is very difficult to perform S-FIL on a flexible substrate successfully due to the high waviness. The waviness of a flexible substrate is not a constant value in contrast to a rigid substrate. It depends on the imprint pressure applied onto the substrate. In this paper, in section two, the effect of the imprint pressure on the waviness of the surface of the flexible substrate is examined. It is proved that the waviness of the surface of the flexible substrate could not be reduced sufficiently to assure a successful imprint at low imprint pressures. In the third section, a method of patterning polymer substrates using ultra-violet nanoimprint lithography (UV-NIL) is presented. The method consists of two stages, stamping-based planarization and S-FIL. In stamping-based planarization, a planarization layer of transparent polymer is formed onto the flexible substrate. Waviness of the blank stamp (in this study, glass wafer) is transferred to the planarization layer. S-FIL is performed with the nanoimprint tool IMPRIO100 directly onto the planarization layer employing a 1 x 1 in. quartz stamp. Optical microscope and SEM images of the successfully imprinted patterns were also presented.
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