Nanoimprint lithography (NIL) is a nonconventional lithographic technique for high-throughput patterning of polymer nanostructures at great precision and at low costs. Unlike traditional lithographic approaches, which achieve pattern definition through the use of photons or electrons to modify the chemical and physical properties of the resist, NIL relies on direct mechanical deformation of the resist material and can therefore achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in conventional techniques. This Review covers the basic principles of nanoimprinting, with an emphasis on the requirements on materials for the imprinting mold, surface properties, and resist materials for successful and reliable nanostructure replication.

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Nanoimprint Lithography: Methods and Material Requirements**

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Newness and distinctiveness is claimed in the features of ornamentation as shown inside the broken line circle in the accompanying representation.

Display screen or portion thereof with graphical user interface

A mobile terminal including a body; a touchscreen provided to a front and extending to side of the body and configured to display content; and a controller configured to detect one side of the body comes into contact with one side of an external terminal, display a first area on the touchscreen corresponding to a contact area of the body and the external terminal and a second area including the content, receive an input of moving the content displayed in the second area to the first area, display the content in the first area, and share the content in the first area with the external terminal.

Mobile terminal and method for controlling the same

Metasurfaces: From microwaves to visible

We report the fabrication of a 50 nm half-pitch wire grid polarizer with high performance using nanoimprint lithography. The device is a form of aluminium gratings on a glass substrate whose size of 5.5 cm × 5.5 cm is compatible with a microdisplay panel. A stamp with a pitch of 100 nm was fabricated on a silicon substrate using laser interference lithography and sidewall patterning. The imprint and the aluminium etching processes are optimized to realize uniform aluminium gratings with aspect ratio of 4. The polarization extinction ratio of the fabricated device is over 2000, with transmission of 85% at a wavelength of 450 nm, which is the highest value ever reported. This work demonstrates that nanoimprint lithography is a unique cost-effective solution for nanopatterning requirements in consumer electronics components.

https://iopscience.iop.org/article/10.1088/0957-4484/16/9/076/pdf

Fabrication of a 50 nm half-pitch wire grid polarizer using nanoimprint lithography

A color filter incorporating a subwavelength patterned grating in a metal film perforated with a square array of circular apertures on a quartz substrate was accomplished. Its performance was enhanced by applying a dielectric overlay to the grating layer so as to match the refractive indices of the media on either side of it. The device was designed by utilizing the finite-difference time-domain method and implemented by adopting the electron-beam direct-writing technique. Two different devices were fabricated with the structural parameters: the grating height of 50 nm and the pitch of 340 nm for the red color and 260 nm for the green color. For the red color filter the center wavelength was 680 nm and the peak transmission 57%, while for the green color one the center wavelength was 550 nm and the peak transmission 50%. It was confirmed the introduction of the index matching overlay led to an increase of ~15% in the transmission efficiency and helped combine double bands into a single dominant band as well, thereby improving the color selectivity of the filter.

Color filter based on a subwavelength patterned metal grating

The nano-imprint lithography method was employed to incorporate wide-area (375×330µm2) photonic-crystal (PC) patterns onto the top surface of GaN-based LEDs. When the 280-nm-thick p-GaN was partly etched to ~140nm, the maximal extraction-efficiency was observed without deteriorating electrical properties. After epoxy encapsulation, the light output of the PC LED was enhanced by 25% in comparison to the standard LED without pattern, at a standard current of 20mA. By three-dimensional finite-difference time-domain method, we found that the extraction efficiency of the LED tends to be saturated as the etch-depth in the GaN epitaxial-layer becomes larger than the wavelength of the guided modes.

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Light extraction enhancement from nano-imprinted photonic crystal GaN-based blue light-emitting diodes.

Photonic crystal (PC) structures on green light emitting diodes (LED) were successfully fabricated using nanoimprint lithography. The stamp, with a two-dimensional pillar structure, was fabricated using laser interference lithography through a double exposure technique. To achieve PC structures with a precise dimension, thermal treatment of the photoresist was employed during stamp fabrication; this proved to be effective for the control of the diameter and shape of the hole. The two-dimensional PC structures, with a period of 295 nm, diameter of 180 nm and depth of 100 nm, on the green LEDs resulted in nine-fold enhancement of the photoluminescence intensity compared to the as-deposited samples without PC structures.

https://iopscience.iop.org/article/10.1088/0957-4484/18/5/055306/pdf

Fabrication of photonic crystal structures on light emitting diodes by nanoimprint lithography

A mobile terminal and its display method are discussed. According to an embodiment, the mobile terminal includes a display unit of a touch screen type divided into at least one of first and second display regions; and a controller that performs a particular function or re-adjusts a divisional boundary between the first and second display regions according to a user's instruction sensed from the display unit, wherein the display unit displays a movable menu bar that partitions the first and second display regions.

Sang Hoon Kim

Papers

Fabrication of a 50 nm half-pitch wire grid polarizer using nanoimprint lithography

Color filter based on a subwavelength patterned metal grating

Light extraction enhancement from nano-imprinted photonic crystal GaN-based blue light-emitting diodes.

Fabrication of photonic crystal structures on light emitting diodes by nanoimprint lithography

Display device and method of mobile terminal