New deposition techniques for amorphous oxide semiconductors compatible with silicon back end of line manufacturing are needed for 3D monolithic integration of thin‐film electronics. Here, three atomic layer deposition (ALD) processes are compared for the fabrication of amorphous zinc tin oxide (ZTO) channels in bottom‐gate, top‐contact n‐channel transistors. As‐deposited ZTO films, made by ALD at 150–200 °C, exhibit semiconducting, enhancement‐mode behavior with electron mobility as high as 13 cm2 V−1 s−1, due to a low density of oxygen‐related defects. ZTO deposited at 200 °C using a hybrid thermal‐plasma ALD process with an optimal tin composition of 21%, post‐annealed at 400 °C, shows excellent performance with a record high mobility of 22.1 cm2 V–1 s–1 and a subthreshold slope of 0.29 V dec–1. Increasing the deposition temperature and performing post‐deposition anneals at 300–500 °C lead to an increased density of the X‐ray amorphous ZTO film, improving its electrical properties. By optimizing the ZTO active layer thickness and using a high‐k gate insulator (ALD Al2O3), the transistor switching voltage is lowered, enabling electrical compatibility with silicon integrated circuits. This work opens the possibility of monolithic integration of ALD ZTO‐based thin‐film electronics with silicon integrated circuits or onto large‐area flexible substrates.

Morpho sulkowskyi butterfly wings contain naturally occurring hierarchical nanostructures that produce structural coloration. The high aspect ratio and surface area of these wings make them attractive nanostructured templates for applications in solar energy and photocatalysis. However, biomimetic approaches to replicate their complex structural features and integrate functional materials into their three-dimensional framework are highly limited in precision and scalability. Herein, a biotemplating approach is presented that precisely replicates Morpho nanostructures by depositing nanocrystalline ZnO coatings onto wings via low-temperature atomic layer deposition (ALD). This study demonstrates the ability to precisely tune the natural structural coloration while also integrating multifunctionality by imparting photocatalytic activity onto fully intact Morpho wings. Optical spectroscopy and finite-difference time-domain numerical modeling demonstrate that ALD ZnO coatings can rationally tune the structural coloration across the visible spectrum. These structurally colored photocatalysts exhibit an optimal coating thickness to maximize photocatalytic activity, which is attributed to trade-offs between light absorption and catalytic quantum yield with increasing coating thickness. These multifunctional photocatalysts present a new approach to integrating solar energy harvesting into visually attractive surfaces that can be integrated into building facades or other macroscopic structures to impart aesthetic appeal.

Interfacial fracture and delamination of polymer interfaces can play a critical role in a wide range of applications, including fiber-reinforced composites, flexible electronics, and encapsulation layers for photovoltaics. However, owing to the low surface energy of many thermoplastics, adhesion to dissimilar material surfaces remains a critical challenge. In this work, we demonstrate that surface treatments using atomic layer deposition (ALD) on poly­(methyl methacrylate) (PMMA) and fluorinated ethylene propylene (FEP) lead to significant increases in surface energy, without affecting the bulk mechanical response of the thermoplastic. After ALD film growth, the interfacial toughness of the PMMA–epoxy and FEP–epoxy interfaces increased by factors of up to 7 and 60, respectively. These results demonstrate the ability of ALD to engineer the adhesive properties of chemically inert surfaces. However, in the present case, the interfacial toughness was observed to decrease significantly with an increase in humidity. This was attributed to the phenomenon of stress-corrosion cracking associated with the reaction between Al2O3 and water and might have a significant implication for the design of these tailored interfaces.

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Multifunctional composites that incorporate nonstructural capabilities such as energy storage, self-healing, and structural health monitoring have the potential to transform load-bearing components in automotive and aerospace vehicles. Imparting electrical conductivity into polymer-matrix composites (PMCs) is an important step in enabling multifunctionality while maintaining mechanical stiffness and strength. In this work, electrically conductive PMCs were fabricated by conformally coating Kevlar 49 woven fabrics with aluminum-doped zinc oxide using atomic layer deposition (ALD). Electrical resistance was measured at the single-fiber, single-tow, and woven fabric levels as a function of coating thickness. The ALD coatings on adjacent fibers merge as their thickness increases, resulting in an interconnected network with improved percolation and lower resistance. After ALD, the fabrics were embedded in an epoxy matrix to manufacture PMCs. The electrical resistance of the composites increased with applied tensile strain, which was attributed to cracking of the conductive coatings. The relative change in resistance as a function of strain varied with coating thickness, which was rationalized by a thin-film fracture mechanics model. This work demonstrates a pathway for scalable and tunable incorporation of electrical conductivity into fiber-reinforced composites without significantly changing their density or load-bearing capabilities.