A Transformative Gold Patterning through Selective Laser Refining of Cyanide

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

Direct Laser Writing (DLW) has been increasingly selected as a microfabrication route for efficient, cost-effective, high-resolution material synthesis and conversion. Concurrently, lasers participate in the patterning and assembly of functional geometries in several fields of application, of which electronics stand out. In this review, recent advances and strategies based on DLW for electronics microfabrication are surveyed and outlined, based on laser material growth strategies. First, the main DLW parameters influencing material synthesis and transformation mechanisms are summarized, aimed at selective, tailored writing of conductive and semiconducting materials. Additive and transformative DLW processing mechanisms are discussed, to open space to explore several categories of materials directly synthesized or transformed for electronics microfabrication. These include metallic conductors, metal oxides, transition metal chalcogenides and carbides, laser-induced graphene, and their mixtures. By accessing a wide range of material types, DLW-based electronic applications are explored, including processing components, energy harvesting and storage, sensing, and bioelectronics. The expanded capability of lasers to participate in multiple fabrication steps at different implementation levels, from material engineering to device processing, indicates their future applicability to next-generation electronics, where more accessible, green microfabrication approaches integrate lasers as comprehensive tools.

Direct Writing of Functional Layer by Selective Laser Sintering of Nanoparticles for Emerging Applications: A Review

Selective laser sintering of nanoparticles enables the direct and rapid formation of a functional layer even on heat-sensitive flexible and stretchable substrates, and is rising as a pioneering fabrication technology for future-oriented applications. To date, laser sintering has been successfully applied to various target nanomaterials including a wide range of metal and metal-oxide nanoparticles, and extensive investigation of relevant experimental schemes have not only reduced the minimum feature size but also have further expanded the scalability of the process. In the beginning, the selective laser sintering process was regarded as an alternative method to conventional manufacturing processes, but recent studies have shown that the unique characteristics of the laser-sintered layer may improve device performance or even enable novel functionalities which were not achievable using conventional fabrication techniques. In this regard, we summarize the current developmental status of the selective laser sintering technique for nanoparticles, affording special attention to recent emerging applications that adopt the laser sintering scheme.

One-Step Template-Free Laser Patterning of Metal Microhoneycomb Structures

Metal microhoneycomb structures have received considerable attention as a type of interaction-efficient functional devices owing to their unique morphology and material properties. Microhoneycomb structures are mainly fabricated using the well-known breath-figure method. However, additional post-treatments are required to produce a metal structure because it is a polymer-based process, and this necessitates expensive, complex, and multi-step fabrication processes. Therefore, a simple, low-cost metal honeycomb fabrication process is necessary. In this paper, the laser patterning of an organometallic solution to produce silver microhoneycomb (Ag microhoneycomb) structures is proposed. Various phenomena such as rapid organic evaporation, silver nanoparticle solidification, and material reorganization from Marangoni flow are found to enable patterning-induced microhoneycomb formation. Parametric studies demonstrate that the pore size can be easily controlled through simple laser parameter changes. In addition, cyclic voltammetry and electrochemical impedance spectroscopy studies confirm the potential electrochemical applications of the Ag microhoneycomb structures based on the variation of electrochemical redox behavior depending on the pore size. Owing to the excellent advantages of one-step laser patterning without any templates, the proposed process will likely promote the practical use of the metal microhoneycomb structures.

Epitaxial Growth of Diamond-Shaped Au1/2Ag1/2CN Nanocrystals on Graphene

Epitaxial synthesis of inorganic nanomaterials on pristine 2D materials is of interest in the development of nanostructured devices and nanocomposite materials, but is quite difficult because pristine surfaces of 2D materials are chemically inert. Previous studies found a few exceptions including AuCN, AgCN, CuCN, and Cu0.5Au0.5CN, which can be preferentially synthesized and epitaxially aligned onto various 2D materials. Here, we discover that Au1/2Ag1/2CN forms diamond-shaped nanocrystals epitaxially grown on pristine graphene surfaces. The nanocrystals synthesized by a simple drop-casting method are crystallographically aligned to lattice structures of the underlying graphene. Our experimental investigations on 3D structures and the synthesis conditions of the nanocrystals imply that the rhombic 2D geometries originate from different growth rates depending on orientations along and perpendicular to 1D molecular chains of Au1/2Ag1/2CN. We also perform in situ TEM observations showing that Au1/2Ag1/2CN nanocrystals are decomposed to Au and Ag alloy nanocrystals under electron beam irradiation. Our experimental results provide an additional example of 1D cyanide chain families that form ordered nanocrystals epitaxially aligned on 2D materials, and reveal basic physical characteristics of this rarely investigated nanomaterial.