In this article, AZoNano discusses the different nanolithography techniques that can be utilized for fabricating ceramic micro- and nanostructures. It also discusses the use of nanomaterials in these processes as well as the recent advances in the field of nanolithography.
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Nanolithography and Its Applications
As the demand for smaller and more complex devices continues to grow, nanolithography, the process of patterning nanoscale structures on a surface, offers a promising solution for producing precise and functional nanoscale structures. Recent advances in nanolithography have led to the development of new materials and techniques, allowing for the creation of nanoscale features with unprecedented precision and control.
Micro/nanofabrication innovations have made it possible to create useful micro/nanoscale photonic devices such as absorbers, solar cells, meta-lenses, and meta-holograms. Advanced fabrication techniques have improved the design flexibility of structural materials, which has improved the performance of these photonic devices. However, it is still difficult to fabricate microscopic structural materials in large quantities with high throughput.
Transfer printing lithography is a new method for deterministically assembling nanomaterials into useful configurations. It uses a stamp to imprint patterns from a donor surface onto a target surface. This technique has high homogeneity, reproducibility, and scalability characteristics. As a result, its potential for high-throughput and useful application has been proven in producing high-quality stretchable devices such as wearable bio-integrated electronics and chemical sensors compatible with varied materials of a printable layer.
A cutting-edge technology called capillary force lithography (CFL) increases production by streamlining processes and reducing turnaround times and costs. Numerous patterning techniques are needed to produce scalable, uniform structures in an easy and repeatable manner due to the use of complex nanostructures in photonic devices and electronics.
The difficulties of large-area manufacturing of submicron structures have also been solved by developing techniques, including electron beam lithography (EBL), ion-beam lithography, dip-pen lithography, and block copolymer (BCP) lithography.
Nanolithography for Ceramics Patterning
Ceramics is a class of materials with unique properties, including high strength, durability, and biocompatibility. They have been used in a wide range of applications, such as building materials, aerospace components, and biomedical implants. The ability to pattern ceramics at the nanoscale has been limited due to the material's inherent brittleness and the challenges associated with working with such a hard and brittle material.
Nanolithography has emerged as a promising solution for patterning ceramics at the nanoscale. Over the past decade, there has been significant progress in developing new nanolithography techniques that enable the creation of precise and functional nanoscale ceramic structures. These advances have opened up new possibilities for using ceramics in various applications, including electronics, photonics, and energy conversion.
In addition to developing new types of ceramics, researchers are also exploring new nanolithography techniques that can be used to pattern ceramics. For example, a technique called soft imprint lithography uses a soft elastomeric stamp to transfer a pattern onto a ceramic substrate. This technique offers several advantages over traditional nanolithography techniques, including lower cost, simpler processing, and the ability to pattern a wider range of materials.
One of the most promising approaches for patterning ceramics at the nanoscale is the use of focused ion beam (FIB) lithography. This technique uses a beam of ions to selectively etch away material from a surface, allowing for the creation of precise and complex patterns. This technique has been used to create a range of ceramic structures, including waveguides, resonators, and photonic crystals.
In addition to electronic and photonic applications, ceramics can also be used to develop microfluidic devices for biomedical and chemical analysis. Microfluidic devices are used in a range of applications, from point-of-care diagnostics to drug discovery. The ability to pattern ceramics at the nanoscale enables the development of microfluidic devices with enhanced performance and functionality.
Nanoimprint lithography (NIL) and microcontact printing use flexible stamps or molds to transfer patterns onto a substrate, allowing for the creation of complex patterns with high resolution and repeatability. They can be used to create ceramic microfluidic devices by imprinting a ceramic material with a pattern of microchannels using a flexible mold.
Use of Nanomaterials in Nanolithography
Nanomaterials are often utilized in nanolithography to develop functional ceramic materials with improved properties. Several studies have reported the utilization of a technique called template-assisted infiltration to create ceramic nanocomposites with improved mechanical properties. This technique involves using a porous template to create a scaffold for the ceramic material, which is then infiltrated with a nanomaterial such as a metal or oxide. The resulting composite material has improved strength and toughness compared to traditional ceramics.
Nanoparticles are also being used in the fabrication of ceramic micro- and nanostructures. Gold nanoparticles are reportedly used to pattern ceramic substrates using electron beam lithography (EBL). The gold nanoparticles were used as a mask, which allowed selective removal of the ceramic material using EBL. This approach offers a simple and cost-effective way to pattern ceramics at the nanoscale.
In a recent study published in the Proceedings of SPIE, the authors explained how ZrO2 sol-gel can be used to create intricate patterns using optical lithography techniques such as mask lithography, colloidal lithography, and nanoimprint lithography.
The research team demonstrated how this versatile sol-gel process could be used in optical applications, as well as how it might be combined with other structuring techniques to create intricate patterns on substrates with different natures and geometries. Scanning electron microscopy, atomic force microscopy, and Raman spectroscopy were used to characterize the as-deposited layers. Additionally, the optical characteristics, as well as the impact of thermal treatment on the refractive index and thickness of the layer were determined.
A study published by Kim et al. discussed the creation of micro-perovskite LEDs, also known as μ-PeLEDs, using capillary force lithography (CFL) for low-cost and large-area μ-LED applications. They showed how the CFL shrinks the pixel size by 10 μm. Additionally, by creating uniform pattern arrays, they developed μ-PeLEDs, which demonstrated an external quantum efficiency of 5.9% at 4 V and verified the effectiveness of devices based on poly(ethylene oxide) concentrations.
Another recent study by Amalathas et al. explored the production of periodic inverted nanopyramid structures in monocrystalline Si solar cells using two UV NIL processes. They achieved nanostructures uniformly over a 3.93-inch2 area. By lowering Fresnel reflection and confining incident light within the solar cells, these structures achieved an increment of 11.73% in power conversion efficiency.
Conclusion and Future Perspective
Self-assembly and soft lithography techniques are promising because they achieve low cost, high throughput, and high productivity, which are challenging to realize using traditional techniques. Soft lithography uses straightforward procedures and reusable stamps to enable patterning on flexible large-area surfaces and quick manufacturing.
Various techniques are used to create colloidal particles, which are then used as photonic crystals to self-assemble into submicron structures. Its capacity for mass production is demonstrated by its low cost and scalability.
BCP has easy and scalable production and adjustable shape and dimension properties when blocks are assembled through mutual attraction. The effective modification of light through devices made possible by these micro/nanofabrication techniques has improved the driving performance of solar cells, metaholograms, and LEDs, in particular.
Future studies should concentrate on using materials with inherent, intrinsic absorption by light-matter interaction in optical frequencies to reach high efficiency. They should also focus on the accuracy of technologies for fabricating nanostructures, which is a significant factor affecting the optical response such as resonance peak, transmission, and reflectance, and structures consisting of multilayer stacks to realize the potential for nano-fabricating integrated photonic devices.
References and Further Reading
Vallejo-Otero, V., et al. (2023). Micro-nanostructuring of ZrO2 sol-gel by optical and nanoimprint lithography on various substrates for optical applications. Proc. SPIE 12497, Novel Patterning Technologies, 124970W. https://doi.org/10.1117/12.2657886
Kim, D. H., et al. (2022). Red-emitting micro PeLEDs for UHD displays by using capillary force lithography. Chemical Engineering Journal, 448, 137727. https://doi.org/10.1016/j.cej.2022.137727
Kim, K., et al. (2019). Facile Nanocasting of Dielectric Metasurfaces with Sub-100 nm Resolution. ACS Applied Materials & Interfaces, 11, 29, 26109–26115. https://doi.org/10.1021/acsami.9b07774
Amalathas, A. P., et al. (2017). Efficient light trapping nanopyramid structures for solar cells patterned using UV nanoimprint lithography. Materials Science in Semiconductor Processing, 57, 54-58. https://doi.org/10.1016/j.mssp.2016.09.032