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Fabrication and Optical Characterization of Photonic Metamaterials
Published in Filippo Capolino, Applications of Metamaterials, 2017
While EBL and FIB nanostructuring are suitable for proof-of-principle studies, their serial nature inhibits the fabrication of metamaterial layers on the scale of usual optical coatings (i.e., on a cm2 scale) at reasonable fabrication cost and time. In contrast, interference lithography has a large corresponding potential, is inexpensive, and is versatile. The basic principle of interference lithography is simple: a photoresist film is exposed to a standing wave pattern arising from the interference of at least two noncoaxial laser beams (ideally plane waves). According to the threshold dose of the resist, the interference pattern is transferred into the photoresist in a digitized form. The developed resist structure can be used as an evaporation or etch mask for further processing.
Interference Lithography
Published in Myeongkyu Lee, Optics for Materials Scientists, 2019
Interference lithography is a powerful technique for fabricating periodic structures. It allows regular arrays of fine features to be patterned without the use of complex optical systems or photomasks. With the advent of short-wavelength and high-power lasers, interference lithography became a very popular manufacturing tool. Photolithography, literally meaning light-stone-writing in Greek, refers to any process that uses light to transfer a geometric pattern from a photomask to a photosensitive material such as photoresist. After development by a series of treatments, the photoresist is used either as an etch mask for the underlying substrate or a template for the deposition of a new material. Although conventional photolithography is well established and widely used in microelectronic industry to create integrated circuits, the required optical system and photomasks are very expensive. Interference lithography, which is based on the interference of several coherent laser beams, can produce periodic patterns over large areas in a much simpler way. The basic principle of interference lithography is the same as in holography. Thus it is also called holographic lithography. An interference pattern between two or more coherent light waves is recorded in a photoresist. This interference pattern represents a periodic series of fringes consisting of intensity maxima and minima. A photoresist pattern corresponding to the periodic intensity pattern emerges upon post-exposure processing. A one-dimensional (1D) pattern is generated by two-beam interference, while three-beam interference produces a 2D pattern. By using four or more beams, 3D structures can be generated. Interference lithography requires that a coherent light source be employed. This is readily achieved with a laser but broadband light sources would require a filter. A laser beam is often used directly without any collimation step. It is first split into two or more beams and then recombined in the region where interference occurs. Beam splitting and recombination are typically carried out by mirrors, prisms, and diffraction gratings. Interfering high-power pulsed laser beams can induce periodic structures on the surface of materials (including metals, ceramics, and polymers) based on photothermal and/or photochemical mechanisms. Using this approach, the material can be directly structured just in a few seconds. Such surface patterns can be effectively utilized for a range of applications including tribology (wear and friction reduction), photovoltaics, and biotechnology. The applicability of interference lithography is limited to patterning arrayed features or uniformly distributed aperiodic structures only. Nevertheless, it has many advantages as a fabrication method for periodic structures. It is a mask-free, low-cost, and scalable process. In addition, it enables the shape and period of the structures to be controlled by adjusting optical parameters such as the number, polarization directions, and incident angles of interfering beams. In this chapter, we describe the basic concepts of interference lithography, together with how 1D, 2D, and 3D periodic structures can be created using this technique.
New Design of Binary to Ternary Converter
Published in IETE Journal of Research, 2023
Reza Akbari-Hasanjani, Reza Sabbaghi-Nadooshan
Based on lent’s statement about reducing dimensions, it is possible to reduce the dimensions to achieve optimal performance, but to build such cells requires equipment building dimensions sub 10 nm. Methods for making devices sub 10 nm can be used the Field Emission Scanning Probe Lithography (FE-SPL) method, which uses FE-SPL to shrink low-energy electrons emitted from the tip of the active concealer [26]. Another method proposed for making dimensions sub 10 nm is the electron beam lithography method with polymethmetacrylate resistor (PMMA), in which the etch line dimensions are reported to be 5–7 nm [27]. Another method of lithography is the use of EUV interference lithography, which uses various masks to shrink and create 6 nm patterns on a 100 nm surface [28]. The plasmonic lithography method was also used to create patterns smaller than 9 nm [29]. In the quantum dot construction, the reported minimum diameter is 1 nm, which uses the In2Te3 semiconductor [30].
Evaluation of effective elastic properties of 3D printable interpenetrating phase composites using the meshfree radial point interpolation method
Published in Mechanics of Advanced Materials and Structures, 2018
A number of processing methods have been used to design and fabricate IPCs. Breslin et al. [8] adopted a liquid phase displacement reaction method to fabricate a co-continuous Al2O3–Al composite. Jhaver and Tippur [3] produced a lightweight IPC by infiltrating an uncured epoxy-based syntactic foam into an open-cell aluminum preform. The resulting IPC has improved properties over conventional syntactic foams. Other approaches, including power metallurgy [9], indirect squeeze casting process [10], and self-propagating high synthesis reaction technique [11], have also been employed to fabricate IPCs. In addition to the above-mentioned processing routes, new manufacturing methods have enabled precise production of IPCs over a wide range of length scales. Interference lithography [12] can produce structures with sub-micron sizes. Furthermore, the three-dimensional (3D) printing technology allows fabrication of components with complex shapes at the millimeter and micron scales [4]. All of these approaches have provided avenues for producing and utilizing IPCs in various industries, including aerospace, automobile, robotics, and smart materials.