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Abstract: The light extraction efficiency of light emitting diode (LED) devices was improved by embedding nano-sized two-dimensional, air cavity photonic crystal (PC) structure on the indium tin oxide (ITO) layer of GaN-based LEDs. The embedded air cavity PC structure was fabricated using a reversal imprint lithography technique. The nano-cavity patterns had a width of 560nm, a space of 240nm and a height of 280nm. According to current–voltage characterization, the electrical performance of the LED devices was not degraded by the fabrication process of air cavity PC structure. The optical output power of the LED device was increased by up to 10% at a drive current of 20mA by forming the nano-cavity PC structure on the transparent electrode of the blue LED device, which was grown on a patterned sapphire substrate, to maximize the photon extraction. Since photons are scattered with cavities and are unaffected by the packaging process, which is the encapsulation of a LED device with epoxy resin, this enhancement in light extraction efficiency will not be decreased after the packaging process. [Copyright &y& Elsevier]

Abstract: In this study, high density phase change nano-pillar device (Tera-bit per inch2 data density) was fabricated on flexible substrates by thermal curing type nanoimprint lithography with high throughput at a relatively low temperature (120°C). Phase change nano-pillar was formed with on flexible poly (ethylene terephthalate) (PET) film, polyimide (PI) film, and stainless steel plate (SUS) substrate without any damage of substrate. The electrical property of the fabricated phase change nano-pillar device was confirmed by electrical signal measuring of conductive atomic force microscopy. [Copyright &y& Elsevier]

Abstract: In this study, the high density nano-pillar type phase change memory was fabricated using duplicating nano-patterns of the anodic alumina oxide (AAO) by nanoimprint process. The high density nano-hole array of AAO template was transferred to the flexible PVC polymer template using hot embossing method. To use the flexible AAO shaped template for UV-NIL, the high density nano-pillar type Ge2Sb2Te5 patterns were fabricated, and the electrical properties of the device were evaluated by conducting atomic force microscopy, connected electrical measurement system. To use the flexible AAO shaped template for UV-NIL, high density GST pattern could be fabricated even on the flexible polyimide (PI) substrate. [ABSTRACT FROM AUTHOR]

Abstract: Nano to micro-sized patterns were formed on a flexible polymer substrate using a flexible UV imprint stamp. A 6in. diameter flexible UV nanoimprint template was fabricated using PVC hot embossing and DLC coating. Using the UV nanoimprint process with the DLC coated PVC template, nano to micro-sized patterns were clearly formed on the flexible PET substrate without a residual layer, due to the antistiction properties and high mechanical hardness of the DLC coating. By depositing a Cr layer on the imprinted resist pattern and lifting it off, Cr metal patterns were fabricated on the PET substrate. [Copyright &y& Elsevier]

Abstract: Phase change memory is one of the most promising non-volatile memory for the next generation memory media due to its simplicity, wide dynamic range, fast switching speed and possibly low power consumption. Low power consuming operation of phase change random access memory (PRAM) can be achieved by confining the switching volume of phase change media into nanometer scale. Nanoimprint lithography is an emerging lithographic technique in which surface protrusions of a mold such as sub-100nm patterns are transferred into a resin layer easily. In this study, crossbar structures of phase change device array based on Ge2Sb2Te5 were successfully fabricated at 60nm scale by two consecutive UV nanoimprint lithography and metal lift-off process, which showed on/off resistance ratio up to 3000. [Copyright &y& Elsevier]

Abstract: DRAM is the most commonly used memory due to many advantages such as high speed and easy manufacturability owing to its simple structure, but is volatile. On the other hand, flash memory is non-volatile, but has other disadvantages such as slow speed, short lifetime, and low endurance for repetitive data writing. Compared to DRAM and flash memory, PRAM (Phase-change Random Access Memory), which is a non-volatile memory using a reversible phase change between amorphous and crystalline state, has many advantages such as high speed, high sensing margin, low operating voltage, and is being pursed as a next generation memory. Being able to pattern and etch phase change memory in nanometer scale is essential for the integration of PRAM. This study uses the Nano-Imprint Lithography (NIL) for patterning the PRAM in nanometer scale which is believed to be a future lithography technology that will replace the conventional Photo Lithography. Si wafers coated with SiO2 were used as substrates, and Ge2Sb2Te5 (GST) films with the thicknesses of 100 nm were deposited by RF sputtering. Poly-benzylmethacrylate based polymer patterns were formed using NIL on the surface of GST films, and the GST films were etched using Cl2/Ar plasma in an Oxford ICP (inductively coupled plasma) etcher. [Copyright &y& Elsevier]

Polymer based complex nanoscale structures were fabricated and transferred to various substrates using reverse nanoimprint lithography. To facilitate the fabrication and transference of the large area of the nanostructured layer to the substrates, a water-soluble polyvinyl alcohol mold was used. After generation and transference of the nanostructured layer, the polyvinyl alcohol mold was removed by dissolving in water. A residue-free, UV-curable, glue layer was formulated and used to bond the nanostructured layer onto the substrates. As a result, nanometer scale patterned polymer layers were bonded to various substrates and three-dimensional nanostructures were also fabricated by stacking of the layers. [ABSTRACT FROM AUTHOR]

Abstract: Fabrication of imprint stamp is a key issue of nanoimprint lithography. In this study, we attempt to fabricate the nickel imprint stamp using hot embossing lithography and electroforming processes. As small as 50nm sized patterns of original silicon master were faithfully transferred to polyvinyl chloride (PVC) film. By electroforming on hot embossed PVC film, nickel stamp, which has the same patterns of original silicon master stamp, was successfully fabricated. [Copyright &y& Elsevier]

Abstract: Phase change random access memory (PRAM) is one of the most promising non-volatile memories due to its ability to store digital data in the form of crystalline and amorphous phases of phase change materials. As a phase change material, Ge2Sb2Te5 (GST225) is usually used, due to its reversible phase transition capability with speeds of less than 100ns between the crystalline and amorphous phases. In order to fabricate highly integrated PRAM devices, sub micron- to nanometer-sized patterning of GST225 layer must be accomplished. In this study, 70nm-sized polymer patterns were fabricated using partial filling nanoimprint lithography (NIL) on a GST225 layer, which was deposited by RF sputtering. Then GST225 was etched using Ar/Cl2 plasma with an ICP etcher. Etch conditions, including Cl2 concentration, were optimized to obtain the vertical etch profile of the GST patterns. [Copyright &y& Elsevier]

Abstract: As a promising substrate for various kinds of devices, polyethylene-terephthalate (PET) film has many advantages in terms of transparency, flexibility, chemical stability, thermal resistance, mechanical strength and low fabrication cost. In order to build actual device structure on PET substrate, micro to nanometer scale patterns of functional material have to be formed. In this work, 70nm sized resist patterns with near zero residual layer were made on PET film, using nanoimprint lithography process, based on ‘partial filling effect’. After brief oxygen plasma treatment and e-beam evaporation of functional materials such as Cr metal, resist patterns were lifted-off with acetone solution and 70nm sized Cr nanowire structure was uniformly formed on flexible PET substrate. [Copyright &y& Elsevier]