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Fabrication of Uniaxially Aligned Silica Nanogrooves with Sub-5 nm Periodicity on Centimeter-Scale Si Substrate Using Poly(dimethylsiloxane) Stamp
摘要： The large-area fabrication of aligned nanopatterns with sub-5 nm feature size is crucial for developing nanodevices. Highly ordered nanostructures fabricated through molecular self-assembly exhibit substantial potential for sub-5 nm patterning techniques. Previously, we had reported the fabrication of silica nanogrooves with sub-5 nm periodicity on a Si substrate by using the outermost surfaces of cylindrical surfactant micelles as a template. However, uniaxial alignment of nanogrooves on the entire substrate surface has not yet been achieved. In this study, uniaxially aligned silica nanogrooves were prepared on the entire surface of a Si substrate (2 × 2 cm) by utilizing a poly(dimethylsiloxane) (PDMS) stamp with a striped pattern. The PDMS stamp was placed on the surface of a surfactant thin film precoated on the substrate, although the stamp was not in direct contact with the substrate as in the case of the soft nanoimprint technique. The substrate was then exposed to water vapor, during which cylindrical micelles were aligned in the direction of the guide. Subsequently, by exposing the substrate to an NH3–water vapor mixture, the outermost surfaces of the aligned micelles facing the substrate were replicated with soluble silicate species. The formation of uniaxially aligned nanogrooves on the entire surface of the centimeter-scale substrate was verified by scanning electron microscopy observations and grazing-incidence small-angle X-ray scattering analysis. Thus, herein we provide a simple large-area fabrication method for uniaxially aligned nanopattern with ultra-fine pitch.
关键词： nanoimprint,nanopatterning,alignment control,directed self-assembly,liquid crystals
更新于2025-09-23 15:23:52
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Macroscopic Alignment of Block Copolymers on Silicon Substrates by Laser Annealing
摘要： Laser annealing is a competitive alternative to conventional oven annealing of block copolymer (BCP) thin films enabling rapid acceleration and precise spatial control of the self-assembly process. Localized heating by a moving laser beam (zone annealing), taking advantage of steep temperature gradients, can additionally yield aligned morphologies. In its original implementation it was limited to specialized germanium-coated glass substrates, that absorb visible light and exhibit low-enough thermal conductivity to facilitate heating at relatively low irradiation power density. Here, we demonstrate a recent advance in laser zone annealing, which utilizes a powerful fiber-coupled near-IR laser source allowing rapid BCP annealing over a large area on conventional silicon wafers. The annealing coupled with photothermal shearing yields macroscopically-aligned BCP films which are used as templates for patterning metallic nanowires. We also report a facile method of transferring laser-annealed BCP films onto arbitrary surfaces. The transfer process allows patterning substrates with a highly corrugated surface and single-step rapid fabrication of multilayered nanomaterials with complex morphologies.
关键词： laser annealing,photothermal processing,block copolymers,nanopatterning,directed self-assembly,multilayers
更新于2025-09-19 17:13:59
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Controlled Gold Nanoparticle Placement into Patterned Polydimethylsiloxane Thin Films via Directed Self-Assembly
摘要： An economically scalable and reproducible method to assemble nanoparticles (NPs) into ordered arrays with high fidelity remains a fundamental roadblock. Methods like directed self-assembly have shown the highest promise resulting in >85% density of NP-filled prepatterned polymer cavities. This work refines directed self-assembly by controlling the evaporation rate, substrate velocity (deposition rate), and NP diameter resulting in reproducible fabrication of ordered arrays with areas >2 mm × 2 mm and ~100% density of filled cavities. Measured optical spectra showed a blueshift in the localized surface plasmon resonance (LSPR) and surface lattice resonance (SLR) peaks with increasing NP density for both 100 and 150 nm gold (Au) NPs. Discrete dipole approximation (DDA), coupled dipole approximation (CDA), rapid semi-analytical CDA (rsa-CDA), and Mie theory simulations closely matched extinction per nanoparticle (extinction/NP) calculations for measured extinction spectra. An ordered array containing 150 nm AuNPs was used for comparison with rsa-CDA estimates using both polydimethylsiloxane (PDMS) and glass refractive indices (RI) resulting in peak location estimates within 1.7% and comparable relative increases in peak heights. Both the measured and simulated SLR peak heights were shown to significantly increase when the array was on glass as opposed to within PDMS.
关键词： directed self-assembly,extinction spectra,gold nanoparticles,surface lattice resonance,localized surface plasmon resonance
更新于2025-09-12 10:27:22
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Printing Birefringent Figures by Surface Tension-Directed Self-Assembly of a Cellulose Nanocrystal/Polymer Ink Components
摘要： Photonic printing on transparent substrates using emerging synthetic photonic crystals is in high demand, especially for anti-fraud applications. However, photonic printing is faced with grand challenges including lack of the full invisibility of printed patterns before stimulation or after stimuli removal and absence of the long-lasting stability. Natural anisotropic crystal structures and artificially molecularly arranged polymers show an optically anisotropic property known as birefringence. Crystalline cellulose is the most abundant birefringent bio-crystal on the earth. Here, we introduce a printing method based on using a cellulose nanocrystal/polymer ink that is governed by surface evaporation phenomenon and divided surface tension forces to direct the self-assembly of ink components at the nanoscale and print 3D birefringent micro-figures on transparent substrates. This type of printing is from now on referred to as Birefringent Printing (BP). Unlike previously reported photonic crystal printing methods, this method is accurate, has high-contrast, is virtually impossible to forge and at the same time is very simple, inexpensive and non-toxic.
关键词： polymer ink,cellulose nanocrystal,directed self-assembly,birefringence,surface tension,invisible printing
更新于2025-09-04 15:30:14