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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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Sub-100 nm 2D nanopatterning on large scale by ultrafast laser energy regulation
摘要： Coupling ultrafast light to surface nanoreliefs leads to periodic patterns achieving record processing scales down to tens of nanometers. Driven by near-field interactions, the promising potential of the spontaneous pattern formation relies on the scale-up manufacturing one-step process. Here, we report the self-assembly of unconventional arrays of nanocavities of 20 nm diameter with a periodicity down to 60 nm upon ultrafast laser irradiation of a nickel surface. In stark contrast to laser-induced surface ripples, which are stochastic and suffer from a lack of regularity, the 2D patterns present an unprecedented uniformity on extreme scales. The onset of nanocavity arrays ordered in a honeycomb lattice is achieved by overcoming the anisotropic polarization response of the surface by a delayed action of cross-polarized laser pulses. The origin of this self-arrangement is identified as a manifestation of Marangoni convection instability in a nanoscale melt layer, destabilized by the laser-induced rarefaction wave.
关键词： nanopatterning,self-assembly,ultrafast laser,Marangoni convection,nanocavities
更新于2025-09-23 15:19:57
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Nanostructures of functionalized zinc phthalocyanines prepared with colloidal lithography: Evaluation of surface orientation and dimensions using scanning probe microscopy
摘要： Patterned arrays of nanoholes and nanorings were prepared using colloidal lithography combined with steps of solution immersion and vapor deposition of organosilanes. Samples prepared with colloidal lithography exhibit millions of reproducible test structures with a periodic arrangement throughout areas of the surface according to the dimensions and spacing of the particle mask. Views of the size and morphology of nanopatterns obtained with atomic force microscopy (AFM) can provide information of progressive steps of chemical reactions as nanostructures are grown within spatially confined areas surrounded by a resist film. A surface mask of colloidal latex or silica spheres was used to protect discrete areas of a Si(111) substrate from the deposition of organosilanes. When the mask was removed, the uncovered areas of the surface revealed regularly-shaped, small sites of uncovered substrate available for further reaction steps to build hierarchical surface structures. Nanostructures of zinc phthalocyanines (ZnPcs) were constructed using amine-terminated nanopatterns as sites for binding. Spatial selectivity was achieved for directing the attachment of ZnPcs to the surface using resist films of 2-[methoxy(polyethyleneoxy)propyl]trichlorosilane (PEO-silane) and also with octadecyltrimethoxysilane (OTMS). The molecule chosen as a linker was (3-aminopropyl)triethoxysilane (APTES) which presents an amine group at the interface. In general, phthalocyanine molecules tend to bind in a coplanar orientation by physisorption to the surface and can stack together through pi-pi interactions between adjacent macrocycles. However, the nature of the substituents will also influence whether the molecules assemble on surfaces in a side-on orientation or with the macrocycle oriented in a coplanar arrangement. Hydroxyl and isothiocyanate pendant groups were attached to the macrocycles of ZnPcs chosen for this study, to investigate conformational differences when attached to APTES nanopatterns. The size and morphology of nanostructures was visualized and sensitively measured with tapping-mode AFM. The elastic response of samples patterned with ZnPc was mapped with force modulation AFM. Changes in the height of nanostructures indicate whether the macrocycles are oriented upright or parallel to the surface plane, or if multilayers were formed.
关键词： Atomic force microscopy,Colloidal lithography,Nanopatterning,Phthalocyanines
更新于2025-09-23 15:19:57
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Influence of Substrates on the Long-Range Order of Photoelectrodeposited Se-Te Nanostructures
摘要： The long-range order of anisotropic phototropic Se-Te films grown electrochemically at room temperature under uniform intensity, polarized, incoherent near-IR illumination has been investigated using crystalline (111)-oriented Si substrates doped degenerately with either p- or n-type dopants. Fourier-transform (FT) analysis was performed on large-area images obtained with a scanning electron microscope, and peak shapes in the FT spectra were used to determine the pattern fidelity in the deposited Se-Te films. Under nominally identical illumination conditions, phototropic films grown on p+-Si(111) exhibited a higher degree of anisotropy and a more well-defined pattern period than phototropic films grown on n+-Si(111). Similar differences in the phototropic Se-Te deposit morphology and pattern fidelity on p+-Si vs. n+-Si were observed when the deposition rate and current densities were controlled for by adjusting the deposition parameters and illumination conditions. The doping-related effects of the Si substrate on the pattern fidelity of the phototropic Se-Te deposits is ascribable to an electrical effect produced by the different interfacial junction energetics between Se-Te and p+-Si vs n+-Si that influences the dynamic behavior during phototropic growth at the Se-Te/Si interface.
关键词： interface,photodeposition,chalcogenide,Electrodeposition,photoelectrochemistry,nanopatterning
更新于2025-09-19 17:15:36
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Grayscale Nanopatterning of Phase-Change Materials for Subwavelength-Scaled, Inherently Planar, Nonvolatile, and Reconfigurable Optical Devices
摘要： The integration of phase-change materials into the design of optical metasurfaces already enables dynamically switchable, tunable, and reconfigurable optical devices. Their functionality is based on fast and repeatable switching between two stable states - amorphous and crystalline - which is typically accompanied by drastic changes of the electrical and optical properties and can be accomplished by external stimuli. In this study, we demonstrate that focused ion beam irradiation can be used to locally tailor the amount of disorder in phase-change materials in highly confined regions, which was examined both in the visible and mid infrared by using optical nano-imaging techniques such as photo-induced force microscopy and scattering type scanning near-field optical microscopy. Our approach enables grayscale patterning at the nanoscale circumventing the diffraction limit of common laser light sources and thus literally adds a further degree of freedom for the design of optical devices that are subwavelength-scaled, inherently planar, nonvolatile, and reconfigurable.
关键词： focused ion irradiation,grayscale,tailoring disorder,nanopatterning,phase-change materials,nano-imaging
更新于2025-09-19 17:13:59
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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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Super-resolution interference lithography enabled by non-equilibrium kinetics of photochromic monolayers
摘要： Highly parallelized optical super-resolution lithography techniques are key for realizing bulk volume nanopatterning in materials. The majority of demonstrated STED-inspired lithography schemes are serial writing techniques. Here we use a recently developed model spirothiopyran monolayer photoresist to study the non-equilibrium kinetics of STED-inspired lithography systems to achieve large area interference lithography with super-resolved feature dimensions. The linewidth is predicted to increase with exposure time and the contrast is predicted to go through a maximum, resulting in a narrow window of optimum exposure. Experimental results are found to match with high quantitative accuracy. The low photoinhibition saturation threshold of the spirothiopyran renders it especially conducive for parallelized large area nanopatterning. Lines with 56 and 92 nm FWHM were obtained using serial and parallel patterning, respectively. Functionalization of surfaces with heterobifunctional PEGs enables diverse patterning of any desired chemical functionality on these monolayers. These results provide important insight prior to realizing a highly parallelized volume nanofabrication technique.
关键词： nanopatterning,spirothiopyran,non-equilibrium kinetics,interference lithography,super-resolution lithography
更新于2025-09-12 10:27:22
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Maskless Micro/Nanopatterning and Bipolar Electrical-Rectification of MoS2 Flakes Through Femtosecond Laser Direct Writing
摘要： MoS2 micro/nanostructures are desirable for tuning electronic properties, developing required functionality, and improving existing performance of multilayer MoS2 devices. This work presents a useful method to flexibly microprocess multilayer MoS2 flakes through femtosecond laser pulse direct writing, which can directly fabricate regular MoS2 nanoribbon arrays with ribbon widths of 179, 152, 116, 98, and 77 nm, and arbitrarily pattern MoS2 flakes to form micro/nanostructures such as single nanoribbon, labyrinth array, and cross structure. This method is mask-free and simple, and has high flexibility, strong controllability, and high precision. Moreover, numerous oxygen molecules are chemically and physically adsorbed on laser-processed MoS2, attributed to roughness defect-sites and edges of micro/nanostructures that contain numerous unsaturated edge-sites and highly active centres. In addition, electrical tests of the field effect transistor fabricated from prepared MoS2 nanoribbon arrays reveal new interesting features: output and transfer characteristics exhibit strong rectification (not going through zero and bipolar conduction) of drain?source current, which is supposedly attributed to the parallel structures with many edge-defects and p-type chemical doping of oxygen molecules on MoS2 nanoribbon arrays. This work demonstrates the ability of femtosecond laser pulses to directly induce micro/nanostructures, property changes, and new device-properties of two-dimension materials, which may future enable new applications at electronic devices based on MoS2 such as logic circuits, complementary circuits, chemical sensors, and p?n diodes.
关键词： micro/nanopatterning,MoS2 flakes,oxygen bonding,femtosecond laser direct writing,electrical rectification
更新于2025-09-12 10:27:22
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Pulsed Laser-Assisted Helium Ion Nanomachining of Monolayer Graphene—Direct-Write Kirigami Patterns
摘要： A helium gas ?eld ion source has been demonstrated to be capable of realizing higher milling resolution relative to liquid gallium ion sources. One drawback, however, is that the helium ion mass is prohibitively low for reasonable sputtering rates of bulk materials, requiring a dosage that may lead to signi?cant subsurface damage. Manipulation of suspended graphene is, milling. We demonstrate that competitive ion beam-induced therefore, a logical application for He deposition from residual carbonaceous contamination can be thermally mitigated via a pulsed laser-assisted He milling. By optimizing pulsed laser power density, frequency, and pulse width, we reduce the carbonaceous byproducts and mill graphene gaps down to sub 10 nm in highly complex kiragami patterns.
关键词： pulsed laser,nanopatterning,graphene,direct-write kirigami
更新于2025-09-11 14:15:04
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Light Emission by Nanoporous GaN Produced by a Top-Down, Nonlithographical Nanopatterning
摘要： Temperature-dependent photoluminescence (PL) spectroscopy is carried out to probe radiative recombination and related light emission processes in two-dimensional periodic close-packed nanopore arrays in gallium nitride (np-GaN). The arrays were produced by nonlithographic nanopatterning of wurtzite GaN followed by a dry etching. The results of Raman spectroscopy point to a small relaxation of the compressive stress of ~0.24 GPa in nanoporous vs. bulk GaN. At ~300 K, the PL emission is induced by excitons and not free-carrier interband radiative recombinations. An evolution of the emission spectra with T is con?rmed to be mainly a result of a decay of nonexcitonic PL emission and less of spectral shifts of the underlying PL bands. A switching of excitonic PL regime observed experimentally was analyzed within the exciton recombination-generation framework. The study provides new insights into the behaviors and physical mechanisms regulating light emission processes in np-GaN, critical to the development of nano-opto-electronic devices based on mesoscopic GaN.
关键词： photoluminescence,nonlithographic nanopatterning,Raman spectroscopy,nanoporous GaN,excitonic emission
更新于2025-09-09 09:28:46