Nanofabrication has limited most optical metamaterials to 2D or, often with multiple patterning steps, simple 3D meta-atoms that typically have limited built-in tunability. Here, with a one-step ...scalable patterning process, we exploit the chemical addressability and structural adaptability of colloidal Au nanocrystal assemblies to transform 2D nanocrystal/Ti bilayers into complex, 3D-structured meta-atoms and to thermally direct their shape morphing and alter their optical properties. By tailoring the length, number, and curvature of 3D helical structures in each meta-atom, we create large-area metamaterials with chiroptical responses of as high as ~40% transmission difference between left-hand (LCP) and right-hand (RCP) circularly polarized light (ΔT = TRCP – TLCP) that are suitable for broadband circular polarizers and, upon thermally configuring their shape, switch the polarity of polarization rotation. Finally, these 3D optical metamaterials provide prototypes for low-cost, large-scale fabrication of optical metamaterials for ultrathin lenses, polarizers, and waveplates.
Ultrathin semiconductor nanowires enable high‐performance chemical sensors and photodetectors, but their synthesis and device integration by standard complementary metal‐oxide‐semiconductor ...(CMOS)‐compatible processes remain persistent challenges. This work demonstrates fully CMOS‐compatible synthesis and integration of parallel‐aligned polycrystalline ZnO nanowire arrays into ultraviolet photodetectors via infiltration synthesis, material hybridization technique derived from atomic layer deposition. The nanowire photodetector features unique, high device performances originating from extreme charge carrier depletion, achieving photoconductive on–off ratios of >6 decades, blindness to visible light, and ultralow dark currents as low as 1 fA, the lowest reported for nanostructure‐based photoconductive photodetectors. Surprisingly, the low dark current is invariant with increasing number of nanowires and the photodetector shows unusual superlinear photoconductivity, observed for the first time in nanowires, leading to increasing detector responsivity and other parameters for higher incident light powers. Temperature‐dependent carrier concentration and mobility reveal the photoelectrochemical‐thermionic emission process at grain boundaries, responsible for the observed unique photodetector performances and superlinear photoconductivity. The results elucidate fundamental processes responsible for photogain in polycrystalline nanostructures, providing useful guidelines for developing nanostructure‐based detectors and sensors. The developed fully CMOS‐compatible nanowire synthesis and device fabrication methods also have potentials for scalable integration of nanowire sensor devices and circuitries.
Infiltration synthesis enables fully complementary metal‐oxide‐semiconductor (CMOS)‐compatible synthesis of parallel‐aligned polycrystalline ZnO nanowire arrays and their integration into ultrasensitive UV detectors featuring ≈1 fA dark currents, the lowest reported for photoconductive photodetectors. The full carrier depletion and photoelectrochemical thermionic emission enable dark currents invariant with increasing number of nanowires, >106 on–off ratios, and unique superlinear photoconductivity, a behavior first observed in nanowires.
A central challenge in developing magnetically coupled quantum registers in diamond is the fabrication of nitrogen vacancy (NV) centers with localization below ∼20 nm to enable fast dipolar ...interaction compared to the NV decoherence rate. Here, we demonstrate the targeted, high throughput formation of NV centers using masks with a thickness of 270 nm and feature sizes down to ∼1 nm. Super-resolution imaging resolves NVs with a full-width maximum distribution of 26 ± 7 nm and a distribution of NV–NV separations of 16 ± 5 nm.
Motivated by the drawbacks of solution phase processing, an all‐dry resist formation process is presented that utilizes amorphous zinc‐imidazolate (aZnMIm) films deposited by atomic/molecular layer ...deposition (ALD/MLD), patterned with electron beam lithography (EBL), and developed by novel low temperature (120 °C) gas phase etching using 1,1,1,5,5,5‐hexafluoroacetylacetone (hfacH) to achieve well‐resolved 22 nm lines with a pitch of 30 nm. The effects of electron beam irradiation on the chemical structure and hfacH etch resistance of aZnMIm films are investigated, and it is found that electron irradiation degrades the 2‐methylimidazolate ligands and transforms aZnMIm into a more dense material that is resistant to etching by hfacH and has a C:N:Zn ratio effectively identical to that of unmodified aZnMIm. These findings showcase the potential for aZnMIm films to function in a dry resist technology. Sensitivity, contrast, and critical dimensions of the patterns are determined to be 37 mC cm−2, 0.87, and 29 nm, respectively, for aZnMIm deposited on silicon substrates and patterned at 30 keV. This work introduces a new direction for solvent‐free resist processing, offering the prospect of scalable, high‐resolution patterning techniques for advanced semiconductor fabrication processes.
A solvent‐free deposition and patterning process has been developed using an inorganic–organic hybrid material comprised of Zn2+ and 2‐methylimidazolate linkers deposited by atomic/molecular layer deposition (ALD/MLD) to yield smooth, amorphous resist films. Using electron beam lithography (EBL), linewidths of 22 nm have been achieved using the vapor phase etchant 1,1,1,5,5,5‐hexafluoroacetylacetone (hfacH) at 120 °C.
Zinc‐Imidazolate Films
In article number 2311149, Michael Tsapatsis, D. Howard Fairbrother, and co‐workers report an all‐dry resist technology based on an amorphous zinc imidazolate metal‐organic ...framework deposited by atomic/molecular layer deposition and developed by low temperature gas phase etching, achieving resolution down to 22 nm. This methodology introduces a new direction for solvent‐free resist processing, enabling scalable, high‐resolution patterning techniques for advanced semiconductor fabrication.
The saturation field of circular islands, consisting of Fe84Cu16/MgO9Fe84Cu16 multilayers, increases with decreasing diameter of the islands. When the diameter of the islands is below 450 nm the ...field induced changes are dominated by a coherent rotation of the moment of the Fe84Cu16 layers. For diameters of 2 μm and larger, a signature of domain nucleation and evolution is observed. The changes in the saturation field with diameter of the islands are ascribed to the interplay between interlayer exchange coupling, stray field coupling at the edges and the crystalline anisotropy of the Fe84Cu16 layers.
Human hair has three main regions, the medulla, the cortex, and the cuticle. An existing model for the cortex suggests that the α-keratin- based intermediate filaments (IFs) align with the hair's ...axis, but are orientationally disordered in-plane. We found that there is a new region in the cortex near the cuticle's boundary in which the IFs are aligned with the hair's axis, but additionally, they are orientationally ordered in-plane due to the presence of the cuticle/hair boundary. Further into the cortex, the IF arrangement becomes disordered, eventually losing all in-plane orientation. We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase. This is direct structural evidence that the cuticle contains β-keratin sheets. This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.
Patterning of materials at single nanometer resolution allows engineering of quantum confinement effects, as these effects are significant at these length scales, and yields direct control over ...electro-optical properties. Silicon is by far the most important material in electronics, and the ability to fabricate Si-based devices of the smallest dimensions for novel device engineering is highly desirable. Here, the work presented here uses aberration-corrected electron-beam lithography combined with dry reactive ion etching to achieve both: patterning of 1-nm features and surface and volume plasmon engineering in Si. The nanofabrication technique employed here produces nanowires with a line edge roughness (LER) of 1 nm (3σ). In addition, this work demonstrates tuning of the Si volume plasmon energy by 1.2 eV from the bulk value, which is one order of magnitude higher than previous attempts of volume plasmon engineering using lithographic methods.
A top‐down lithographic patterning and deposition process is reported for producing nanoparticles (NPs) with well‐defined sizes, shapes, and compositions that are often not accessible by wet‐chemical ...synthetic methods. These NPs are ligated and harvested from the substrate surface to prepare colloidal NP dispersions. Using a template‐assisted assembly technique, fabricated NPs are driven by capillary forces to assemble into size‐ and shape‐engineered templates and organize into open or close‐packed multi‐NP structures or NP metamolecules. The sizes and shapes of the NPs and of the templates control the NP number, coordination, interparticle gap size, disorder, and location of defects such as voids in the NP metamolecules. The plasmonic resonances of polygonal‐shaped Au NPs are exploited to correlate the structure and optical properties of assembled NP metamolecules. Comparing open and close‐packed architectures highlights that introduction of a center NP to form close‐packed assemblies supports collective interactions, altering magnetic optical modes and multipolar interactions in Fano resonances. Decreasing the distance between NPs strengthens the plasmonic coupling, and the structural symmetries of the NP metamolecules determine the orientation‐dependent scattering response.
Nanoparticles (NPs) are produced with lithographic fabrication and assembled into open or close‐packed structures using a template‐assisted assembly technique. The NP assemblies’ coordination number, interparticle gap size, disorder, and voids are controlled by the shapes and sizes of the NPs and templates. Tuneable Fano resonances are obtained in the dark‐field scattering spectra of the assembly.
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