Maskless fabrication of plasmonic metasurfaces in polymer film using a spatial light modulator

We demonstrate a high-speed optical technique to fabricate plasmonic metasurfaces in a polymer film. The technique is based on a programmable spatial light modulator, which is used to spatially control the photoreduction sites of gold ions in a polyvinyl alcohol film doped with a gold precursor. After irradiation, annealing was used to induce the growth of nanoparticles, producing plasmonic microstructures. Using a 473 nm excitation wavelength, microscopic plasmonic gratings, and meta-atom arrays with arbitrary orientations, an effective nanostructure size of ∼700 nm and constituent nanoparticles with average size of ∼37 nm were created. The technique enables a cost-effective and straightforward light-based approach to fabricate plasmonic metasurfaces with tunable properties.acceptedVersionPeer reviewe

Nanogap Device: Fabrication and Applications

A nanogap device as a platform for nanoscale electronic devices is presented. Integrated nanostructures on the platform have been used to functionalize the nanogap for biosensor and molecular electronics. Nanogap devices have great potential as a tool for investigating physical phenomena at the nanoscale in nanotechnology. In this dissertation, a laterally self-aligned nanogap device is presented and its feasibility is demonstrated with a nano ZnO dot light emitting diode (LED) and the growth of a metallic sharp tip forming a subnanometer gap suitable for single molecule attachment. For realizing a nanoscale device, a resolution of patterning is critical, and many studies have been performed to overcome this limitation. The creation of a sub nanoscale device is still a challenge. To surmount the challenge, novel processes including double layer etch mask and crystallographic axis alignment have been developed. The processes provide an effective way for making a suspended nanogap device consisting of two self-aligned sharp tips with conventional lithography and 3-D micromachining using anisotropic wet chemical Si etching. As conventional lithography is employed, the nanogap device is fabricated in a wafer scale and the processes assure the productivity and the repeatability. The anisotropic Si etching determines a final size of the nanogap, which is independent of the critical dimension of the lithography used. A nanoscale light emitting device is investigated. A nano ZnO dot is directly integrated on a silicon nanogap device by Zn thermal oxidation followed by Ni and Zn blanket evaporation instead of complex and time consuming processes for integrating nanostructure. The electrical properties of the fabricated LED device are analyzed for its current-voltage characteristic and metal-semiconductor-metal model. Furthermore, the electroluminescence spectrum of the emitted light is measured with a monochromator implemented with a CCD camera to understand the optical properties. The atomically sharp metallic tips are grown by metal ion migration induced by high electric field across a nanogap. To investigate the growth mechanism, in-situ TEM is conducted and the growing is monitored. The grown dendrite nanostructures show less than 1nm curvature of radius. These nanostructures may be compatible for studying the electrical properties of single molecule

Optically Induced Nanostructures

Nanostructuring of materials is a task at the heart of many modern disciplines in mechanical engineering, as well as optics, electronics, and the life sciences. This book includes an introduction to the relevant nonlinear optical processes associated with very short laser pulses for the generation of structures far below the classical optical diffraction limit of about 200 nanometers as well as coverage of state-of-the-art technical and biomedical applications. These applications include silicon and glass wafer processing, production of nanowires, laser transfection and cell reprogramming, optical cleaning, surface treatments of implants, nanowires, 3D nanoprinting, STED lithography, friction modification, and integrated optics. The book highlights also the use of modern femtosecond laser microscopes and nanoscopes as novel nanoprocessing tools

Laser-induced forward transfer (LIFT) of water soluble polyvinyl alcohol (PVA) polymers for use as support material for 3D-printed structures

The additive microfabrication method of laser-induced forward transfer (LIFT) permits the creation of functional microstructures with feature sizes down to below a micrometre [1]. Compared to other additive manufacturing techniques, LIFT can be used to deposit a broad range of materials in a contactless fashion. LIFT features the possibility of building out of plane features, but is currently limited to 2D or 2½D structures [2–4]. That is because printing of 3D structures requires sophisticated printing strategies, such as mechanical support structures and post-processing, as the material to be printed is in the liquid phase. Therefore, we propose the use of water-soluble materials as a support (and sacrificial) material, which can be easily removed after printing, by submerging the printed structure in water, without exposing the sample to more aggressive solvents or sintering treatments. Here, we present studies on LIFT printing of polyvinyl alcohol (PVA) polymer thin films via a picosecond pulsed laser source. Glass carriers are coated with a solution of PVA (donor) and brought into proximity to a receiver substrate (glass, silicon) once dried. Focussing of a laser pulse with a beam radius of 2 µm at the interface of carrier and donor leads to the ejection of a small volume of PVA that is being deposited on a receiver substrate. The effect of laser pulse fluence , donor film thickness and receiver material on the morphology (shape and size) of the deposits are studied. Adhesion of the deposits on the receiver is verified via deposition on various receiver materials and via a tape test. The solubility of PVA after laser irradiation is confirmed via dissolution in de-ionised water. In our study, the feasibility of the concept of printing PVA with the help of LIFT is demonstrated. The transfer process maintains the ability of water solubility of the deposits allowing the use as support material in LIFT printing of complex 3D structures. Future studies will investigate the compatibility (i.e. adhesion) of PVA with relevant donor materials, such as metals and functional polymers. References: [1] A. Piqué and P. Serra (2018) Laser Printing of Functional Materials. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. [2] R. C. Y. Auyeung, H. Kim, A. J. Birnbaum, M. Zalalutdinov, S. A. Mathews, and A. Piqué (2009) Laser decal transfer of freestanding microcantilevers and microbridges, Appl. Phys. A, vol. 97, no. 3, pp. 513–519. [3] C. W. Visser, R. Pohl, C. Sun, G.-W. Römer, B. Huis in ‘t Veld, and D. Lohse (2015) Toward 3D Printing of Pure Metals by Laser-Induced Forward Transfer, Adv. Mater., vol. 27, no. 27, pp. 4087–4092. [4] J. Luo et al. (2017) Printing Functional 3D Microdevices by Laser-Induced Forward Transfer, Small, vol. 13, no. 9, p. 1602553

New generation electron beam resists: a review

The semiconductor industry has already entered the sub-10 nm region, which has led to the development of cutting-edge fabrication tools. However, there are other factors that hinder the best outcome of these tools, such as the substrate and resist materials, pre- and postfabrication processes, etc. Among the lithography techniques, electron beam lithography (EBL) is the prime choice when a job requires dimensions lower than 10–20 nm, since it can easily achieve such critical dimensions in reasonable time and effort. When obtaining pattern features in single nanometer regime, the resist material properties play an important role in determining the size. With this agenda in mind, many resists have been developed over the years suitable for attaining required resolution in lesser EBL writing time. This review article addresses the recent advancements made in EBL resists technology. It first describes the different lithography processes briefly and then progresses on to the parameters affecting the EBL fabrications processes. EBL resists are then bifurcated into their “family types” depending on their chemical composition. Each family describes one or two examples of the new resists, and their chemical formulation, contrast-sensitivity values, and highest resolution are described. The review finally gives an account of various alternate next-generation lithography techniques, promising dimensions in the nanometer range

Direct-Write Ion Beam Lithography

Patterning with a focused ion beam (FIB) is an extremely versatile fabrication process that can be used to create microscale and nanoscale designs on the surface of practically any solid sample material. Based on the type of ion-sample interaction utilized, FIB-based manufacturing can be both subtractive and additive, even in the same processing step. Indeed, the capability of easily creating three-dimensional patterns and shaping objects by milling and deposition is probably the most recognized feature of ion beam lithography (IBL) and micromachining. However, there exist several other techniques, such as ion implantation- and ion damage-based patterning and surface functionalization types of processes that have emerged as valuable additions to the nanofabrication toolkit and that are less widely known. While fabrication throughput, in general, is arguably low due to the serial nature of the direct-writing process, speed is not necessarily a problem in these IBL applications that work with small ion doses. Here we provide a comprehensive review of ion beam lithography in general and a practical guide to the individual IBL techniques developed to date. Special attention is given to applications in nanofabrication

Nanolithography on non-planar surfaces and self-assembly of metal salt-polymer nanomaterials

This thesis is focused on fabrication of high aspect ratio nanostructures on non-planar surfaces using evaporated electron beam resist (Part I), and a novel fabrication methods of high resolutionhigh-resolution surface nanostructures using metal salt: polymer nanocomposites self-assembly (Part II). Various top-down and bottom-up nanopatterning techniques are currently available with the rapid progress in instrumentation and material engineering. However, patterning on non-planar surfaces of various materials still remains an overwhelming challenge because the conventional resist coating method, spin-coating, works well for only planar surfaces such as a flat wafer. On the other hand, the ability to pattern any given surface at the nanoscale, in particular surfaces with high inherent roughness or with pre-patterned micro-scale features, opens new perspectives in various fields from multi-scale biomimetics to optoelectronics. Part I (Chapter 1-4) of the present thesis aims to address this issue using evaporated electron beam resist. Electron beam lithography (EBL) is a versatile technique for creating arbitrary patterns on substrates with sub-10 nm resolution. Contrary to conventional lithography techniques, EBL was previously shown to be able to pattern non-planar surfaces using modified lithography system to adjust the beam position along z-axis, spray coating of the resist, and evaporation of the resist. Among them, evaporation of the resist is more favorable as it can be done on any irregular surfacesurfaces using commonly available thermal evaporation equipment. Yet, previous evaporated resist materials suffer from low resolution and sensitivity, as well as poor dry etching resists for subsequent pattern transfer to the sub-layer. Here, evaporation of polystyrene electron beam resist is studied which was used to pattern on irregular surfaces such as the cantilever of atomic force microscope and side surface of an optical fiber. Furthermore, in order to drastically increase the resist’s dry etching resistance, chromium that is a hard etching mask material was successfully incorporated into the resist by co-evaporating or Cr and polystyrene. This nanocomposite resist enabled the fabrication of very high aspect ratio structures by electron beam lithography followed by dry plasma etching. As this material can be evaporated on any substrate, including non-planar surfaces, it can open new era to spectroscopy and bio-sensing techniques. Part II (Chapter 5-6) presents a low-cost bottom-up fabrication techniques for creatingto create dense surface nanostructures without long-range ordering. Recently, micro- and nano-structured surfaces have become a hot topic in nanotechnology where performance of devices is enhanced due to such surface nanostructuring. Such structures are often called as a “smart” coating on the surfaces where they could provide wetting/de-wetting, adhesion, thermal and/or electrical conductivity, super-hydrophobicity, self-cleaning, anti-icing, anti-reflectivity, etc. Bottom-up techniques, such as self-assembly lithography, areis undoubtedly much more cost-effective than top down lithography techniques for applications that do not need long range ordering. Block co-polymer lithography, colloidal lithography, sol-gel processing, wet/dry etching are some commonly used techniques of bottom-up fabrication. However, fabrication of those structures with low costslow-cost as well as high performance is still challenging. Here a novel fabrication method is introduced, which involves spin-coating of metal salt : polymer composite followed by its phase-separation upon thermal annealing. Both spin-coating and thermal annealing are very low- cost processes. With this method, after pattern transfer to the substrate using the self-formed metal salt islands as mask, dense and high resolutionhigh-resolution nanostructures over large area without long-range ordering is achieved, which offered greatly enhanced super-hydrophobic and anti-reflective properties

Structuring and functionalization of non-metallic materials using direct laser interference patterning: A review

Direct laser interference patterning (DLIP) is a laser-based surface structuring method that stands out for its high throughput, flexibility and resolution for laboratory and industrial manufacturing. This top-down technique relies on the formation of an interference pattern by overlapping multiple laser beams onto the sample surface and thus producing a periodic texture by melting and/or ablating the material. Driven by the large industrial sectors, DLIP has been extensively used in the last decades to functionalize metallic surfaces, such as steel, aluminium, copper or nickel. Even so, DLIP processing of non-metallic materials has been gaining popularity in promising fields such as photonics, optoelectronics, nanotechnology and biomedicine. This review aims to comprehensively collect the main findings of DLIP structuring of polymers, ceramics, composites, semiconductors and other non-metals and outline their most relevant results. This contribution also presents the mechanisms by which laser radiation interacts with non-metallic materials in the DLIP process and summarizes the developed surface functions and their applications in different fields.Fil: Mulko, Lucinda. Technische Universität Dresden; AlemaniaFil: Soldera, Marcos Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Lasagni, Andrés Fabián. Technische Universität Dresden; Alemani