Fabrication of microprisms for planar optical interconnections by use of analog gray-scale lithography with high-energy-beam-sensitive glass

For an integrated free-space optical interconnection system we suggest the use of microprisms to achieve large coupling angles at low loss. Prisms were fabricated in photoresist and quartz glass by analog lithography. High-energy-beam-sensitive glass was used as the gray-tone mask. Optical testing of the prisms shows acceptable surface quality and high efficiency (95%).     

Fabrication of conjugated polymer nanowires by edge lithography

This paper describes the fabrication of conjugated polymer nanowires by a three stage process: (i) spin-coating a composite film comprising alternating layers of a conjugated polymer and a sacrificial material, (ii) embedding the film in an epoxy matrix and sectioning it with an ultramicrotome (nanoskiving), and (iii) etching the sacrificial material to reveal nanowires of the conjugated polymer. A free-standing, 100-layer film of two conjugated polymers was spin-coated from orthogonal solvents: poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) from chloroform and poly(benzimidazobenzophenanthroline ladder) (BBL) from methanesulfonic acid. After sectioning the multilayer film, dissolution of the BBL with methanesulfonic acid yielded uniaxially aligned MEH-PPV nanowires with rectangular cross sections, and etching MEH-PPV with an oxygen plasma yielded BBL nanowires. The conductivity of MEH-PPV nanowires changed rapidly and reversibly by >10 (3) upon exposure to I 2 vapor. The result suggests that this technique could be used to fabricate high-surface-area structures of conducting organic nanowires for possible applications in sensing and in other fields where a high surface area in a small volume is desirable.     

Fabrication of two-dimensional superposed microstructure by interference lithography

In this paper, we report the basic theory and method of single exposure interference lithography (IL) to fabricate two-dimensional (2D) superposed microstructures. Distribution of six-beam interference intensities with different azimuth angle is discussed, and 2D superposed microstructures with different periodic constants are obtained by computer simulations. The experiment results using CHP-C positive photoresist show a 2D superposed photonic crystal composed of a periodically repeated hexagonal pattern of hexagonal lattice cells, which is in close agreement with the computer simulation. Fabrication of a superposed structure by single exposure IL paves the way for studying 2D photonic crystal fabrication, surface lasing, optical waveguides, and so on.     

Fabrication of mid-infrared frequency-selective surfaces by soft lithography

We describe the fabrication of large areas (4 cm(2)) of metallic structures or aperture elements that have ~100-350-nm linewidths and act as frequency-selective surfaces. These structures are fabricated with a type of soft lithography-near-field contact-mode photolithography-that uses a thin elastomeric mask having topography on its surface and is in conformal contact with a layer of photoresist. The mask acts as an optical element to create minima in the intensity of light delivered to the photoresist. Depending on the type of photoresist used, lines of, or trenches in, photoresist are formed on the substrate by exposure, development, and lift-off. These surfaces act as bandpass or bandgap filters in the infrared.     

Fabrication of polypyrrole-based nanoelectrode arrays by colloidal lithography

This paper describes a novel technique to produce polypyrrole-based nanoelectrodes for electrochemical detection purpose. The fabrication process relies on the creation of patterned nanotemplates i.e., nanometric gold spots surrounded by an electrically insulating material (SiO(x)). From these templates, polypyrrole nanopillars are grown by classical electrochemical methods. Atomic force microscopy demonstrates that polypyrrole grows selectively inside the gold nanotemplates. The electrochemical characterization by cyclic voltammetry showed a sigmoidal-shaped voltammogram characterizing the typical nanoelectrode array behavior.     

Precise and simple optical alignment method for double-sided lithography

A method for aligning a photolithographic mask at the top of a transparent wafer that has a pattern on its bottom side is presented. The method is based on optical self-imaging of special alignment marks and provides submicrometer accuracy. The method is simple and robust and can conveniently be implemented on laboratory mask aligners for contact or proximity printing.     

Fabrication of moth eye structures via charged nanoparticle lithography with size and density control

We have developed and demonstrated an effective method for fabricating the moth eye structures formed by charged nanoparticle lithography (cNPL). We attached high-density gold nanoparticles (Au NPs) to GaN without aggregation by making the surface of Au NPs negatively charged and GaN positively charged. Au NPs were effectively used as an etching mask, and the moth eye structures of GaN were formed by inductively coupled plasma reactive ion etching. The moth eye structures with various sizes and densities were fabricated by the cNPL, and the moth eye structures reduced the reflectance. The cNPL, as a simple technique with size and density control, will provide high potential to optical device applications.     

Fabrication of large number density platinum nanowire arrays by size reduction lithography and nanoimprint lithography

Large number density Pt nanowires with typical dimensions of 12 microm x 20 nm x 5 nm (length x width x height) are fabricated on planar oxide supports. First sub-20 nm single crystalline silicon nanowires are fabricated by size reduction lithography, and then the Si nanowire pattern is replicated to produce a large number of Pt nanowires by nanoimprint lithography. The width and height of the Pt nanowires are uniform and are controlled with nanometer precision. The nanowire number density is 4 x 10(4) cm(-1), resulting in a Pt surface area larger than 2 cm(2) on a 5 x 5 cm(2) oxide substrate. Bimodal nanowires with different width have been generated by using a Pt shadow deposition technique. Using this technique, alternating 10 and 19 nm wide nanowires are produced.     

Fabrication of 3D copper oxide structure by holographic lithography for photoelectrochemical electrodes

We fabricated three-dimensional copper oxide structure by holographic lithography and electroless deposition. A five-beam interference pattern defined a woodpile structure of SU-8. The surface modification of SU-8 structure was achieved by multilayer coating of polyelectrolyte, which is critical for activating the surface for the reduction of copper. Copper was deposited onto the surface of the structure by electroless deposition, and subsequent calcinations removed the SU-8 structure and simultaneously oxidized the copper into copper oxide. The porous copper oxide structure was used as a photoelectrochemical electrode. Because of the highly porous structure, our structure showed higher photocurrent efficiency.     

Fabrication of functional nano-patterned surfaces by a combination of plasma processes and electron-beam lithography

This work presents a method for the fabrication of well defined chemically active nano-patterned surfaces. Electron-beam lithography has been combined with plasma-based processes in order to create sub-micron carboxylic functional areas over a non-bio-adhesive matrix. Characterization of the patterned surface by several surface analysis techniques reveals that this patterning technique is compatible with the plasma polymerization process in order to fabricate chemically active features with lateral size down to 300?nm. Moreover, experiments with a model protein (bovine serum albumin) on the patterned surfaces show preferential adhesion on the active region indicating the ability of this method for the design of biosensing platforms.     

Fabrication of advanced fiber Bragg gratings by use of sequential writing with a continuous-wave ultraviolet laser source

We present a novel scheme based on sequential writing for fabrication of advanced fiber Bragg gratings. As opposed to earlier sequential methods this technique uses a cw UV laser source and allows for very precise control and repetitivity of the formation of the gratings. Furthermore it is possible to use high average irradiances without destroying the fiber, resulting in considerable reduction in fabrication time for complex gratings. The method has been applied to several test gratings, which proved its versatility and quality.     

Fabrication and application of polyimide plastic molds for nanoimprint lithography

In this work, we have developed low-cost, high modulus, flexible, and UV transparent polyimide plastic molds for nanoimprint lithography (NIL). Different structures of poly(amic acids) (PAA) and polyimides (PI) have been synthesized. By casting the PAA or PI solutions on a silicon master, flexible but still rigid plastic molds can be produced. The advantages of the PI molds are: (1) high glass-transition temperatures (Tg) up to 310 degrees C, (2) high thermal stability over 500 degrees C, (3) high tensile modulus, and (4) UV transparency for use in UV-NIL. Various micrometer and nanometer scale patterns could be obtained from the PI molds on a large area (4 inch wafer). The imprinting results showed that the PI molds could be faithfully used for both hot embossing NIL and UV-NIL.     

有机太阳能电池ITO电极的光刻制备法及其研究

目前有机太阳能电池是光电行业研究的热点之一。通常该器件以ITO为阳极，通过真空蒸镀的方法制作。在对器件进行测试时，ITO电极的设计制作，有利于器件的保护。用光刻技术进行ITO电极的制作，可以得到非常精细的结果。重点阐述了利用光刻方法制作优良ITO电极的注意点，包括表面清洗、曝光控制、显影控制和腐蚀工艺，其中由于不同ITO玻璃的导电层厚度、各成分含量不同，所以腐蚀工艺的研究是重点中的重点。提供了对生成光刻ITO电极的质量进行准确评价的一种简便方法。     

Fabrication of periodic metal nanowires with microscale mold by nanoimprint lithography

In this paper, a simple method is demonstrated for fabricating periodic metal nanowires based on the unconventional nanoimprint lithography (NIL) technique. Using this method, sub-100 nm metal nanowires with the rectangular cross-section are fabricated with microscale stamp. Furthermore, the metal nanowires with different widths and heights can be generated by adjusting the imprinting parameters with the same stamp. The metal nanowires prepared with this method can be used for chemical sensing, such as ammonia sensing, and it may have applications in optical signal processing.     

Fabrication of fluorine-doped diamond-like carbon stamps for UV nanoimprint lithography

Two fluorine-doped diamond-like carbon (F-DLC) stamps with sub-100 nm line patterns were fabricated using a direct etching method. These were applied successfully to ultraviolet (UV) nanoimprint lithography without requiring an anti-adhesion layer coating. Tests were performed to determine the optimum fluorine concentration for the F-DLC stamps. The ideal stamp material consisted of 25?at.% F-DLC with a contact angle of 85°, UV transmittance of 16.4-26.8%, and hardness of 4.5?GPa. The O(2) plasma etch rate of the DLC was increased considerably by the fluorine doping, making it comparable to the etch rate of polymethyl methacrylate (PMMA). Thus, only PMMA was used as the etch mask in the fabrication of the stamps.     

Molecular-scale soft imprint lithography for alignment layers in liquid crystal devices

We describe molecular-scale soft nanoimprint lithographic replication of rubbed polyimide substrates to form alignment layers for liquid crystal devices. Systematic studies of the surface relief morphology of the polyimide and molded structures in three different polymers illustrate good lithographic fidelity down to relief heights of several nanometers, and with some capabilities at the level of approximately 1 nm. Collective results of experiments with several polymer formulations for molds and molded materials and process conditions indicate that this molecular-scale fidelity in replication can be used to produce surfaces that will effectively align liquid crystal molecules. Good electro-optical responses from liquid crystal light modulators that are formed in this manner suggest utility for fundamental studies and potential practical application.     

Fabrication of molecular nanotemplates in self-assembled monolayers by extreme-ultraviolet-induced chemical lithography

Extreme-UV interference lithography (EUV-IL) is applied to create chemical nanopatterns in self-assembled monolayers (SAMs) of 4'-nitro-1,1'-biphenyl-4-thiol (NBPT) on gold. X-ray photoelectron spectroscopy shows that EUV irradiation induces both the conversion of the terminal nitro groups of NBPT into amino groups and the lateral crosslinking of the underlying aromatic cores. Large-area ( approximately 2 mm(2)) nitro/amino chemical patterns with periods ranging from 2000 nm to 60 nm can be generated. Regions of pristine NBPT on the exposed samples are exchanged with protein-resistant thiol SAMs of polyethyleneglycol, resulting in the formation of molecular nanotemplates, which can serve as the basis of complex biomimetic surfaces.     

Fabrication and photoluminescence properties of graphite fiber/ZnO nanorod core-shell structures

Graphite fiber/ZnO nanorod core-shell structures were synthesized by thermal evaporation process. The core-shell hybrid architectures were comprised of ZnO nanorods grown on the surface of graphite fiber. In addition, Hollow ZnO hierarchical structure can be obtained by oxidizing the graphite fiber. Room temperature photoluminescence (PL) of the as-made graphite fiber/ZnO nanorod structures shows two UV peaks at around 3.274 eV and 3.181 eV. The temperature-dependent photoluminescence spectra demonstrate the two UV emissions are attributed to the intrinsic optical transitions and extrinsic defect-related emissions in ZnO. These hybrid structures may be used as the building block for fabrication of nanodevices.     

Fabry-Perot resonator composed of a photoinduced birefringent fiber grating

The periodic mode coupling between the x- and y-polarization modes that is induced by a photoinduced birefringent fiber grating is analyzed through the use of the coupled-mode theory. A novel Fabry-Perot resonator composed of a photoinduced birefringent fiber grating is proposed and theoretically investigated. In the ideal case, the x- and y-polarization resonances of the resonator coincide with each other because of the polarization power exchange by the photoinduced birefringent grating, which results in the total resonator output's being polarization independent. However, if there are some external perturbations (e.g., temperature change or strain), the phase matching is detuned, which could destroy the coincidence between the two polarization resonances, which can further result in the total output resonance's having two peaks. The separation between these two resonant peaks depends on perturbations of the environment (temperature changes or strain).     

Mode-hop-free single-longitudinal-mode erbium-doped fiber laser frequency scanned with a fiber ring resonator

We describe the experimental construction of a single-longitudinal-mode erbium-doped fiber ring laser equipped with a ring resonator filter. The system is designed to avoid mode hopping and can be frequency scanned for spectroscopic sensor applications. We modified a conventional ring resonator filter to have the capability to reduce transmittance of unwanted modes, which is essential for frequency scanning without mode hopping.