Laser Interference Lithography Technique Research Articles

Real-Time Imaging of Plasmonic Concentric Circular Gratings Fabricated by Lens-Axicon Laser Interference Lithography.

Concentric circular gratings are diffractive optical elements useful for polarization-independent applications in photonics and plasmonics. They are usually fabricated using a low-throughput and expensive electron beam lithography technique. In this paper, concentric circular gratings with selectable pitch values were successfully manufactured on thin films of azobenzene molecular glass using a novel laser interference lithography technique utilizing Bessel beams generated by a combined lens-axicon configuration. This innovative approach offers enhanced scalability and a simplified manufacturing process on larger surface areas compared to the previously reported techniques. Furthermore, the plasmonic characteristics of these concentric circular gratings were investigated using conventional spectrometric techniques after transferring the nanostructured patterns from azobenzene to transparent gold/epoxy thin films. In addition, the real-time imaging of surface plasmon resonance colors transmitted from the concentric circular gratings was obtained using a 45-megapixel digital camera. The results demonstrated a strong correlation between the real-time photographic technique and the spectroscopy measurements, validating the efficacy and accuracy of this approach for the colorimetric studying of surface plasmon resonance responses in thin film photonics.

Laser Interference Lithography—A Method for the Fabrication of Controlled Periodic Structures

A microstructure determines macro functionality. A controlled periodic structure gives the surface specific functions such as controlled structural color, wettability, anti-icing/frosting, friction reduction, and hardness enhancement. Currently, there are a variety of controllable periodic structures that can be produced. Laser interference lithography (LIL) is a technique that allows for the simple, flexible, and rapid fabrication of high-resolution periodic structures over large areas without the use of masks. Different interference conditions can produce a wide range of light fields. When an LIL system is used to expose the substrate, a variety of periodic textured structures, such as periodic nanoparticles, dot arrays, hole arrays, and stripes, can be produced. The LIL technique can be used not only on flat substrates, but also on curved or partially curved substrates, taking advantage of the large depth of focus. This paper reviews the principles of LIL and discusses how the parameters, such as spatial angle, angle of incidence, wavelength, and polarization state, affect the interference light field. Applications of LIL for functional surface fabrication, such as anti-reflection, controlled structural color, surface-enhanced Raman scattering (SERS), friction reduction, superhydrophobicity, and biocellular modulation, are also presented. Finally, we present some of the challenges and problems in LIL and its applications.

Laser interference additive manufacturing ordered Cu microstructure

Here, we explored a novel additive manufacturing method on microscale for metal, carrying out direct laser interference lithography technique under the liquid phase. 3D ordered Cu microstructures with a spatial period of 12 μm could be obtained by this method using the nanosecond laser at the wavelength of 1064 nm with a pulse duration of 5–8 ns. Therefore, the phenomenon of the molten interconnected between Cu2O particles become obvious gradually with the increase of the laser fluence. Furthermore, the height of the microstructure can be tuned by pulse number at the constant laser fluence, which was confirmed by optical microscopy. Finally, the effective method is represented for the additive manufacturing of 3D ordered metal microstructure, which can avoid the environmental pollution by metal microparticles.

Incidence Angle Effects on the Fabrication of Microstructures Using Six-Beam Laser Interference Lithography

This paper presents a theoretical demonstration of diverse microstructure fabrication by changing the angle of incidence of a six-beam laser interference lithography system. Different combinations are formed with transverse electric (TE) and transverse magnetic (TM) polarizations and various microstructures are simulated by controlling the high-reflectivity mirror group to adjust the incidence angle. This study indicates that the incidence angle has a considerable influence on the shape and period of the lattice, thereby contributing to the fabrication of microstructures with different arrangements. These structures include donut, circle, D-type, rectangular, triangular, U-type, and honeycomb lattices. The six-beam laser interference lithography technique is expected to benefit microstructure fabrication because of its simple operation, large writing area, and low cost, thereby promoting the development of micro-optics.

360 nm Continuous Wave Laser-Based Contact or Non-Contact Laser Interference Nano Lithography.

LIL (laser interference lithography), which does not require a mask, is an effective way to create a wide variety of periodic patterns by exposing two laser beams on a specimen. The LIL method can be used for a wide range of nano-pattern spacing by adjusting the laser intensity, exposure time, and development time. In addition, it has been used in many studies due to its advantage with regard to the forming of nanostructures over a large area in a short period of time. However, the existing LIL technique requires demanding precision levels to align the laser beam. In this paper, we attempt to solve this problem by using a prism laser interferometer to complement the complicated beam alignment of LIL. In this study, ma-p1205 PR-coated silicon wafers were exposed to a CW laser with 360 nm wavelength using a contact-type and a non-contact prism interferometer. A rectangular triangular prism and an equilateral triangular prism of N-BK7 were used, and periods of 300 nm and 260 nm were fabricated, respectively. The MATLAB and COMSOL programs were used to compare the theoretical values and fabricated patterns.

Patent Review on Laser Interference Lithography Technique for Producing Periodic Nanostructure.

Because line width has been close to atom size, for semiconductor industry, except for achieving the target of line width, the cost will be more important. The mask-less laser interference lithography (LIL) technique lowers the cost makes it standing out in the market of lithographic equipment of the excessive cost in the semiconductor industry. The Keywords of patent retrieval with the theme of LIL are based on the technical features of both the conditions of producing interference lithography and different types of experimental configuration of LIL. Method of patent retrieval include Boolean logic operators are used to express the relationship between sets. Furthermore, it's necessary to find whether common patent classification codes exist in the highly correlated patents and confirm the definition of that. The patent review in this research show the patents of LIL technique are classified according to optical method and lithographic equipment. The patents related to optical method of LIL technique take beam splitter based configuration as the main stream; in the technique of lithographic equipment, the patents of system planning technique are the most. The findings of this review confirm the importance of improving the precision of LIL technique for avoiding the defocus of high-density line width. Besides, it's particularly suitable for the micro nanofluid device in the emerging bionanotechnology to observe fluid behavior at the minimum scale. It doesn't need mask and can produce periodic pattern with nanoscale make it devote to the field of periodicity.

Large scale fabrication of asymmetric 2D and 3D micro/nano array pattern structures using multi-beam interference lithography technique for Solar cell texturing application

A method for the large scale fabrication of nano/micro array patterned structure for solar Photovoltaics (PV) is demonstrated by the use of laser interference lithography (LIL) technique. Since micro/nano array patterned structures for photonic arrangement are of increasing importance in higher efficiency solar PV cell concepts, structuring technique and miniaturization in size play a vital role in their realization/fabrication. In this paper, we have designed and modelled multi-beam interference lithography technique (MBIL) for the fabrication of solar PV cells. The generated periodic 1D, 2D and 3D micro/nano array structures are done using MATLAB. The obtained results show that the complexity of the pattern structures varies with the variation in position of beams and angle of incidence. The interference parameters such as wavelength, slit separation, distance between slit and screen influence in generation of periodic array pattern structures. The maximum intensity occurs at an angle of incidence 45 degree. The obtained pattern structures have the periodicity of 0.19 µm for 1064 nm, 0.18 µm for 1024 nm, 0.14 µm for 780 nm, 0.12 µm for 650 nm and 0.07 µm for 565 nm. Depth of the focus is found to be 0.029 µm for 1064 nm, 0.028 µm for 1024 nm, 0.024 µm for 780 nm, 0.020 µm for 650 nm and 0.015 µm for 565 nm. MBIL can be applied in fabrication of 3D photonic crystals, magnetic storage, solar cells, waveguides, calibration grids, Organic Light Emitting Diodes (OLEDs) and functional surfaces of sensors.

Design and tailoring of patterned ZnO nanostructures for energy conversion applications

ZnO is a typical direct wide-bandgap semiconductor material, which has various morphologies and unique physical and chemical properties, and is widely used in the fields of energy, information technology, biomedicine, and others. The precise design and controllable fabrication of nanostructures have gradually become important avenues to further enhancing the performance of ZnO-based functional nanodevices. This paper introduces the continuous development of patterning technologies, provides a comprehensive review of the optical lithography and laser interference lithography techniques for the controllable fabrication of ZnO nanostructures, and elaborates on the potential applications of such patterned ZnO nanostructures in solar energy, water splitting, light emission devices, and nanogenerators. Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure, enlarged surface area, and improved light capture ability, which realize the efficient carrier regulation, achieve highly efficient energy conversion, and meet the diverse requirements of functional nanodevices. The patterning techniques proposed for the precise design of ZnO nanostructures not only have important guiding significance for the controllable fabrication of complex nanostructures of other materials, but also open up a new route for the further development of functional nanostructures.

Light‐sheet based lithography technique for patterning an array of microfluidic channels

We propose a Light-sheet laser interference lithography technique for fabricating periodic microfluidic channels. This technique uses multiple light-sheet illumination pattern that is generated using a spatial filter at the back-aperture of the cylindrical lens. Specially designed spatial filter is used that give rise to a periodic pattern at the focal plane which is essentially a 1D Fourier transform of the spatial filter transfer function. One-dimensional focusing property of the cylindrical lens result in the generation of line shaped channel geometry. To design microfluidic channels, the illumination pattern is exposed to the glass substrate coated with a photopolymer sensitized to 532 nm and subsequently developed using standard chemical protocols. Experimentally, the 1D periodic channel structure has an approximate width and periodicity of approximately 11.25 microns. Light-sheets based lithography technique offer a fast and single-shot process to generate microfluidic channels.

Enhanced field emission properties from carbon nanotube emitters on the nanopatterned substrate

The authors investigated the field emission characteristics of printed carbon nanotubes (CNTs) on KOVAR substrates with micro- and nanosize line patterns. Microsized line patterns were fabricated using photolithography techniques followed by an inductive coupled plasma-reactive ion etching process, and laser interference lithography techniques were used to fabricate uniform nanosized patterns over a relatively large area. CNTs were printed on the patterned substrate using a screen printing method. The field emission characteristics of each patterned substrate were compared to those of a nonpatterned substrate. Results revealed that varying the pattern size has an influence on the field emission characteristics. The reduction of the pattern size results in an increase in the total surface area. This surface patterning is found to provide additional areas for CNTs to adhere to the substrates, which, in turn, results in better adhesion of CNTs. As the size of the pattern is reduced, the field emission properties are improved. Specifically, substrates with nanosized patterns exhibited both the lowest turn-on field and the highest field enhancement factor (β).

Diffraction efficiency and noise analysis of hidden image holograms

The simplified approach for analysis of hidden image holograms is discussed in this paper. Diffraction efficiency and signal to noise ratio of reconstructed images were investigated using direct measurements technique and digitized image analysis employing “ImageJ” software. All holograms were recorded in a photoresist layer spin-coated on glass substrates applying laser interference lithography technique. Both analogue and digital analysis approaches showed the similar results thus confirming the appropriateness of the used analysis methods. It was found that holograms recorded at higher laser energy densities demonstrated improved diffraction efficiency and reduced signal to noise ratio of the reconstructed image. The best diffraction efficiency at sufficient signal to noise ratio was obtained using exposure energy density in the range from 150 to 200J/m2 during the hologram writing process.

Long-Range Hexagonal Arrangement of TiO2 Nanotubes by Soft Lithography-Guided Anodization

Long range hexagonally ordered TiO2 nanotube arrangements have been synthesized by employing a novel strategy consisted of combining the well-known Laser Interference Lithography technique together with electrochemical anodization methods. By properly tuning the fabrication parameters that make match between both techniques, TiO2 nanotube arrays having near 32nm of inner diameter, wall thickness around of 25nm and 210nm of lattice parameter were anodically grown on pre-patterned Ti foils over large sample surface areas, typically of several squared centimetres in size. This opens the possibility to the development of new types of functional devices based on self-organized morphologies of anodic TiO2 nanotubes, requiring both high spatially ordered and defect-free nanotube arrangements.

Large arrays of ultra-high aspect ratio periodic silicon nanowires obtained via top–down route

Metal-catalysed etching (MCE) is a simple and versatile method for fabrication of silicon nanowires, of high structural quality. When combined with laser interference lithography (LIL), large areas of periodic structures can be generated in only few steps. The aspect ratio of such periodic structure is however commonly not higher than several decades or very few hundred. Here, a combined MCE and LIL techniques were applied to fabricate dense (4 × 108 cm−3), periodic arrays of vertically aligned silicon nanowires with aspect ratio of up to 103. This is a considerable higher number than previously reported on for periodic silicon wire arrays prepared with top–down approaches. The wires were slightly tapered, with top and bottom diameters ranging from 370 to 195 nm and length of up to 200 μm. A potential use of the nanowires as light absorber is demonstrated by measuring reflection in integrating sphere. An average total absorption of ~97 % was observed for 200-μm-long wires in the spectral range of 450–1000 nm. A comparison to simulated absorption spectra is given.

Development of Nanohole Array Patterned by Laser Interference Lithography Technique

Periodic nanohole pattern was created in spin-coated photoresist S1805 on Si substrates by Laser Interference Lithography (LIL). Wavelength of a laser source used in the optical system is 442 nm with the photon energy 2.80 eV. The system was set up to employ two laser beams from a beam splitter to generate interference pattern and expose to the photoresist. There are two parameters (incident angle and exposure time) which are determined due to affecting the ordering and feature of nanohole array. Therefore, the relation of these two parameters and actual dose were investigated and theoretically analyzed to optimize the resolution of LIL technique for nanoholes. The prepared samples after developing in the M26A for 5 sec were analyzed by field-emission scanning electron microscopy (FE-SEM). The results show that the pitch of the pattern is 440 nm and the smallest hole size is 190 nm The best feature is found for a laser fluence of 140 mJ/cm2. This nanohole array patterned by LIL consists of periodic nanostructures for high density storage to fabricate various nanodevices.

Fabrication of large-area 3D optical fishnet metamaterial by laser interference lithography

Centimeter-scale 3D fishnet metamaterial with negative refractive index in the near infrared spectral range is demonstrated. The large-area fabrication is realized using a conventional laser interference lithography technique in combination with a tri-layer lift-off procedure. This method allows us to effectively achieve a centimeter-scale 3D fishnet structure with a pitch of 600 nm and five functional Ag/SiO2 bi-layers with a total thickness of 300 nm. The experimental transmission spectrum correlates well with simulation results. Effective refractive index versus frequency associated with permittivity and permeability are retrieved. Two negative refractive index regions are found in the near-infrared spectral range.

Development of Multi Scale Structured Al/Al<SUB>2</SUB>O<SUB>3</SUB> Nanowires for Controlled Cell Guidance

Cell responses to surface and contact cell guidance are of great interest in bio-applications especially on nano- and micro scale features. Recently we showed selective cell responses on Al/Al2O3, bi-phasic nanowires (NWs). In this context, Al/Al2O3 NWs were synthesized by the chemical vapor deposition of (tBuOAIH2)2. Afterwards, linear periodic nano- and micro structured NWs were formed using laser interference lithography (LIL) technique to study the contact guidance of neurons from rat dorsal root ganglion (DRG), human umbilical vein smooth muscle cells (HUVSMC), human umbilical vein endothelial cells (HUVEC) and human osteoblast (HOB). LIL treatment did not alter surface chemistry of NWs. From our preliminary research LIL patterned NWs lead to alignment of axons contrary to non-patterned NWs. Morphology of HUVSMC changed from poly- to linear shapes and strong alignment was observed while HUVEC and HOB were not affected.

Improved efficiency in GaAs solar cells by 1D and 2D nanopatterns fabricated by laser interference lithography

We demonstrate an improvement in efficiency of GaAs solar cells using front surface texturing with dielectric 1D and 2D nanopatterns obtained by a low cost laser interference lithography technique. The strong light scattering by the surface dielectric nanopatterns effectively increases the optical path of the incident light in the absorber layers resulting in an efficiency increase up to 23.5% compared to that of the reference solar cell. The observed efficiency improvement in the studied solar cells shows the potential use of low cost photoresist as an antireflection coating material and further application of other robust dielectric materials as texturing layer.

Laser interference lithography and nanoimprint techniques for lower reflection transparent conducting oxide hybrid films

The transparent conducting oxide (TCO) film is a significant component in flat panel display industry, applied for flexible display, e-paper, and touch panel. The TCO materials have high refractive index, so the phenomenon of high reflectance is the major issue and needs solved in present and future market. In this study, the structure and process of new lower reflection TCO hybrid film is introduced. The laser interference lithography and UV nanoimprint are combined for fabrication of sub-wavelength structures on PET film, then the tin-doped indium oxide (ITO) deposited on structures. Finally, the best result of this hybrid film is reflectance reduced to 3.3% at wavelength 550nm, just 13% of the original film, and the resistance of ITO layer is 1.05×10−3 Ω-cm. This result is useful for the TCO film applied in low reflection demand products in the future.

Study on wetting properties of periodical nanopatterns by a combinative technique of photolithography and laser interference lithography

This study presents the wetting properties, including hydrophilicity, hydrophobicity and anisotropic behavior, of water droplets on the silicon wafer surface with periodical nanopatterns and hierarchical structures. This study fabricates one- and two-dimensional periodical nanopatterns using laser interference lithography (LIL). The fabrication of hierarchical structures was effectively achieved by combining photolithography and LIL techniques. Unlike conventional fabrication methods, the LIL technique is mainly used to control the large-area design of periodical nanopatterns in this study. The minimum feature size for each nanopattern is 100 nm. This study shows that the wetting behavior of one-dimensional, two-dimensional, and hierarchical patterns can be obtained, benefiting the development of surface engineering for microfluidic systems.

Superhydrophobic surface structures in thermoplastic polymers by interference lithography and thermal imprinting

We present a method to produce superhydrophobic surfaces in thermoplastic polymer substrates. The method involves the creation of a nickel stamp using a customized laser interference lithography technique and electroplating processes. This stamp is used to emboss sub-micrometer periodic structures into the thermoplastic. The modified surface is coated with a hydrophobic plasma-polymerized hexafluoropropene layer. Surfaces with different periodicity and relief depth were created. On the surface with the highest aspect ratio, advancing water contact angles of 167° were measured with a water contact angle hysteresis of below 5°.