Nanoscale Patterns Research Articles

Advanced ice lithography system using a micro-machined Joule-Thomson cooler

This study introduces a novel ice lithography system integrated with a low-vibration micro-machined Joule-Thomson cooler. Ice lithography is an eco-friendly method for high-resolution nanofabrication on delicate substrates and requires to operate below 130 K in the vacuum of a microscope chamber. Previously, liquid nitrogen rather than cryocoolers was used to cool the system due to its low vibration, but it is both bulky and costly. To overcome these challenges, this study employs a low-vibration micro-machined cooler in a scanning electron microscope (SEM) for ice lithography. The design and methodology of the system are described in detail. The results show that the substrate can reach a temperature of 105 K within 30 minutes with a measured mechanical vibration of less than 10 nm, enabling high-resolution nanofabrication. As proof of concept, the system successfully fabricates nanoscale patterns on a silicon wafer. This low-vibration cooling system has great potential for use in cryogenic electron microscopes (cryo-EMs) in the future.

Nanoscale speckle patterning for combined high‐resolution strain and orientation mapping of environmentally sensitive materials

AbstractScanning electron microscopy‐based high‐resolution digital image correlation (HRDIC) is now an established technique, providing full‐field strain and displacement measurement at the microscale. Techniques for generating speckle patterns for sub‐micron strain mapping can often be either substrate dependent or rely on applying aggressive conditions which may alter the microstructure of interest or damage the substrate in highly sensitive materials. We detail a modification of a methodology successfully applied in the literature to allow its use with metallic materials that are particularly sensitive to the corrosive media, such as copper‐base alloys. Nanometre‐thick silver films, applied with physical vapour deposition, are remodelled using NaBr in non‐aqueous isopropanol, replacing the aqueous solution of NaCl in the original method, forming a uniform dispersion of silver islands highly suitable for digital image correlation (DIC) measurement. The entire procedure is performed at ambient temperature. We find that the DIC pattern is suitably electron transparent to allow electron backscatter diffraction (EBSD) measurements without pattern removal, producing diffraction patterns of sufficient quality for cross‐correlation based high‐angular resolution EBSD. This property facilitates simultaneous EBSD and DIC mapping experiments, providing deeper insights into the kinematics of plastic deformation in crystalline materials. Sub‐100 nm islands are achieved through control of the sputter coating parameters, resulting in DIC cross‐correlation subwindows of 140 nm with a 50% overlap. This resolution is sufficient to capture the fine detail of strain localisation phenomena during plastic deformation, demonstrated here with a case study in CuCrZr, a precipitation‐hardened heat sink material for application in nuclear fusion components. Here, we extract full‐field displacement data with DIC and corresponding orientation information using EBSD without the need for pattern removal.

Interfacial phase-change and geometry modify nanoscale pattern formation in irradiated thin films

Interfacial phase-change and geometry modify nanoscale pattern formation in irradiated thin films

Improving the water-repellent properties of carbon nanotube-polycarbonate composites by introducing nanoscale patterns into the injection molding process

In this study, we explore the impact of hydrophobic nanomaterials, specifically carbon nanotubes (CNTs), on the water repellency of composite materials. These composites are prepared by combining multilayered or single-layered CNTs with polycarbonate (PC). Our goal was to develop highly water-repellent materials by directly forming nanopatterns on the surface through injection molding to enhance water repellency. Irrespective of the CNT type, widening the spacing between surface patterns and increasing the CNT concentration from 0 to 30 wt% resulted in a notable increase in the water contact angle to 161°, surpassing that of Teflon (108°). Moreover, in the multilayered CNT/PC system, a reduction in the sliding angle was observed compared to that of pure polycarbonate, demonstrating a lotus effect-like trend. Conversely, in the case of single-layered CNTs, despite an increase in the contact angle, the sliding angle did not decrease as significantly as in the multilayered CNTs. This implies that the superior transferability during the injection molding process of multilayered CNT/PC compared to single-layered CNT/PC is the underlying factor. This technology holds promise not only in the realm of mobility, such as in the aviation and automotive industries, but also in the medical field, with applications in microfluidic devices.

Improved hydrodynamic properties and enhanced resistance to particle deposition and membrane fouling by millimeter-scale patterned membranes

Membrane fouling is considered a persistent challenge in membrane technology for water and wastewater treatment. Membrane surface patterning is a chemical-free means of controlling membrane fouling. Previous studies mainly focused on nano- and micro-scale patterns, with little attention paid on millimeter-scale patterns on the membrane surface. In this study, the millimeter-scale patterned microfiltration membranes with different pattern heights (PM50, PM55 and PM60) were fabricated, the performances in resisting particle deposition and membrane fouling with synthetic wastewater were examined compared with flat-sheet membrane (FM), and the underlying hydrodynamic mechanism was unveiled using computational fluid dynamics (CFD). CFD simulation results reveal that compared to micro- and nano-scale patterns, millimeter-scale patterns exert a notable increase in maximum velocity, average shear stress and maximum shear stress. All the three millimeter-scale patterned membranes exhibit superior resistance to both particle deposition and membrane fouling than FM, owing to the improvement of hydrodynamic properties instead of enlarged membrane area. PM55 shows the lowest flux decline ratios and least particle/foulant deposition among the three millimeter-scale patterned membranes in both particle deposition and membrane fouling experiments. Pattern height plays a crucial role, as small pattern height cannot generate significant vortices, while high pattern height leads to flow separation. For PM55, the vortices form in the valley regions and locate close to bulk flow, which help transport the deposited particles or foulants back to the bulk flow. The design of pattern configuration is suggested to be tailored based on particle size. Future research can focus on the pilot testing of millimeter-scale patterned membranes, as well as the long-term stability with actual influent.

Antibody Nanotweezer Constructing Bivalent Transistor-Biomolecule Interface with Spatial Tolerance.

Establishing a multivalent interface between the biointerface of a living system and electronic device is vital to building intelligent bioelectronic systems. How to achieve multivalent binding with spatial tolerance at the nanoscale remains challenging. Here, we report an antibody nanotweezer that is a self-adaptive bivalent nanobody enabling strong and resilient binding between transistor and envelope proteins at biointerfaces. The antibody nanotweezer is constructed by a DNA framework, where the nanoscale patterning of nanobodies along with their local spatial adaptivity enables simultaneous recognition of target epitopes without binding stress. As such, effective binding affinity increases by 1 order of magnitude compared with monovalent antibody. The antibody nanotweezer operating on transistor offers enhanced signal transduction, which is implemented to detect clinical pathogens, showing ∼100% overall agreement with PCR results. This work provides a perspective of engineering multivalent interfaces between biosystems with solid-state devices, holding great potential for organoid intelligence on a chip.

Fabrication of nanoscale stencils through focused ion beam milling and dry transfer of silicon-on-nothing membrane with perforations

Nanoscale stencil lithography, providing sub-micrometer resolutions, is being implemented as a reliable patterning technique within the nanotechnology domain. Despite their advantages such as no resist processing, easy manipulation and reusability, patterning using a nanoscale stencil often faces challenges due to the gap between the nanoscale stencil and the substrate. This tends to result in unwanted pattern blurring, typically dimension wider than intended design. To address this issue, we minimize the gap by conformally attaching the nanoscale stencil to the substrate, thereby effectively eliminating a key factor contributing to the blurring effect. The nanoscale stencil is fabricated by forming nanoslits on the 50 nm thick Silicon-on-Nothing (SON) membrane with perforations, using focused ion beam (FIB) milling. The transfer of this stencil onto a substrate enables conformal adhesion due to its 1012 times lower flexural rigidity of the stencil compared to bulk silicon. Upon deposition of chromium and gold through the transferred stencil, a metal pattern array with the full width at half maximum (FWHM) of 43 nm is produced, demonstrating the potential of our approach for fabricating uniform nanoscale patterns with enhanced pattern resolution.

Ultrafast Solid-State Electrochemical Imprinting Utilizing Polymer Electrolyte Membrane Stamps for Static/Dynamic Structural Coloration and Letter Encryption.

Micro and nanopatterned surfaces hold potential for various applications, such as wettability control, antibiofouling, and optical components. However, conventional patterning processes are characterized by complexity, high costs, and environmental burdens because of the use of resists. Therefore, this paper proposes facile and ultrafast electrochemical imprinting employing a polymer electrolyte membrane (PEM) stamp for achieving micro and nanoscale patterning on Si surfaces. The solid-state electrochemical process efficiently generates oxide and hydrated oxide (Si-OH) patterns within several seconds at room temperature in a dry ambient environment. The formed oxide pattern can be employed as an etching mask to prepare diffraction gratings with diverse high-resolution (≈100nm) patterns utilizing the dry PEM stamp. The resulting oxide pattern on the Si surface exhibits instantaneous structural coloration upon exposure to humid air, attributable to the formation of a water microdroplet array on the oxide pattern. The oxide pattern is successfully applied for dynamic diffraction grating and letter encryption. The proposed solid-state electrochemical oxidation scheme based on a PEM stamp, which eliminates the need for liquid electrolyte and resist, represents a simple and ultrafast process with a time cost of a few seconds, characterized by low processing costs and environmental impact.

Mesoporous nanoperforators as membranolytic agents via nano- and molecular-scale multi-patterning

Plasma membrane lysis is an effective anticancer strategy, which mostly relying on soluble molecular membranolytic agents. However, nanomaterial-based membranolytic agents has been largely unexplored. Herein, we introduce a mesoporous membranolytic nanoperforators (MLNPs) via a nano- and molecular-scale multi-patterning strategy, featuring a spiky surface topography (nanoscale patterning) and molecular-level periodicity in the spikes with a benzene-bridged organosilica composition (molecular-scale patterning), which cooperatively endow an intrinsic membranolytic activity. Computational modelling reveals a nanospike-mediated multivalent perforation behaviour, i.e., multiple spikes induce nonlinearly enlarged membrane pores compared to a single spike, and that benzene groups aligned parallelly to a phospholipid molecule show considerably higher binding energy than other alignments, underpinning the importance of molecular ordering in phospholipid extraction for membranolysis. Finally, the antitumour activity of MLNPs is demonstrated in female Balb/c mouse models. This work demonstrates assembly of organosilica based bioactive nanostructures, enabling new understandings on nano-/molecular patterns co-governed nano-bio interaction.

Nanopatterned Monolayers of Bioinspired, Sequence-Defined Polypeptoid Brushes for Semiconductor/Bio Interfaces.

The ability to control and manipulate semiconductor/bio interfaces is essential to enable biological nanofabrication pathways and bioelectronic devices. Traditional surface functionalization methods, such as self-assembled monolayers (SAMs), provide limited customization for these interfaces. Polymer brushes offer a wider range of chemistries, but choices that maintain compatibility with both lithographic patterning and biological systems are scarce. Here, we developed a class of bioinspired, sequence-defined polymers, i.e., polypeptoids, as tailored polymer brushes for surface modification of semiconductor substrates. Polypeptoids featuring a terminal hydroxyl (-OH) group are designed and synthesized for efficient melt grafting onto the native oxide layer of Si substrates, forming ultrathin (∼1 nm) monolayers. By programming monomer chemistry, our polypeptoid brush platform offers versatile surface modification, including adjustments to surface energy, passivation, preferential biomolecule attachment, and specific biomolecule binding. Importantly, the polypeptoid brush monolayers remain compatible with electron-beam lithographic patterning and retain their chemical characteristics even under harsh lithographic conditions. Electron-beam lithography is used over polypeptoid brushes to generate highly precise, binary nanoscale patterns with localized functionality for the selective immobilization (or passivation) of biomacromolecules, such as DNA origami or streptavidin, onto addressable arrays. This surface modification strategy with bioinspired, sequence-defined polypeptoid brushes enables monomer-level control over surface properties with a large parameter space of monomer chemistry and sequence and therefore is a highly versatile platform to precisely engineer semiconductor/bio interfaces for bioelectronics applications.

Multi- and Gray-Scale Thermal Lithography of Silk Fibroin as Water-Developable Resist for Micro and Nanofabrication.

Silk fibroin (SF) is a natural material with polymorphic structures that determine its water solubility and biodegradability, which can be altered by exposing it to heat. Here, a hybrid thermal lithography method combining scalable microscale laser-based patterning with nanoscale patterning based on thermal scanning probe lithography is developed. The latter enables in addition grayscale patterns to be made. The resolution limit of the writing in silk fibroin is studied by using a nanoscale heat source from a scanned nanoprobe. The heat thereby induces local water solubility change in the film, which can subsequently be developed in deionized water. Nanopatterns and grayscale patterns down to 50nm lateral resolution are successfully written in the silk fibroin that behaves like a positive tone resist. The resulting patterned silk fibroin is then applied as a mask for dry etching of SiO2 to form a hard mask for further nano-processing. A very high selectivity of 42:1 between SiO2 and silk fibroin is obtained allowing for high-aspect ratio structure to be fabricated. The fabricated nanostructures have very low line edge roughness of 5±2nm. The results demonstrate the potential of silk fibroin as a water-soluble resist for hybrid thermal lithography and precise micro/nanofabrication.

Fabrication and Characterization of Nano-Structured ZnS:Cu LED

A wide range of Light Emitting Diodes (LEDs) applications, from general lighting to transmission sources of the Visual Light Communication (VLC) system, makes the LEDs very important to be developed. This research focuses on comparing LED performance due to the variation in surface size and shape of the LED. The research method is carried out with a simulation and an experimental approach. Before the experiment, the LED was simulated with nanopattern variations to determine the best fabrication parameter. The simulation method is carried out using Ansys Lumerical FDTD 2021. The experiment method used to fabricate nanopatterns on the surface of a semiconductor LED layer uses the nanoimprint lithography method. Stamps for nanoimprint lithography are made using Polydimethylsiloxane (PDMS), and the nanopattern sources are obtained from DVD and Blu-ray grating patterns. The characterization of nanoscale patterns was carried out using a Scanning Electron Microscope (SEM). The light emission intensity is measured using a lux meter at a series of emission angles. The results obtained from this research are that the smaller the width and the periodicity of the grating nanopattern, the light produced will be distributed at a wider angle, but the light intensity will decrease; conversely, for a planar surface without a grating nanopattern, level of focus and intensity of light will be higher. In addition, the thicker the ZnS:Cu layer, the better the intensity of the light produced.

4D‐STEM Nanoscale Strain Analysis in van der Waals Materials: Advancing beyond Planar Configurations

Achieving nanoscale strain fields mapping in intricate van der Waals (vdW) nanostructures, like twisted flakes and nanorods, presents several challenges due to their complex geometry, small size, and sensitivity limitations. Understanding these strain fields is pivotal as they significantly influence the optoelectronic properties of vdW materials, playing a crucial role in a plethora of applications ranging from nanoelectronics to nanophotonics. Here, a novel approach for achieving a nanoscale‐resolved mapping of strain fields across entire micron‐sized vdW nanostructures using four‐dimensional (4D) scanning transmission electron microscopy (STEM) imaging equipped with an electron microscope pixel array detector (EMPAD) is presented. This technique extends the capabilities of STEM‐based strain mapping by means of the exit‐wave power cepstrum method incorporating automated peak tracking and K‐means clustering algorithms. This approach is validated on two representative vdW nanostructures: a two‐dimensional (2D) MoS2 thin twisted flakes and a one‐dimensional (1D) MoO3/MoS2 nanorod heterostructure. Beyond just vdW materials, the versatile methodology offers broader applicability for strain‐field analysis in various low‐dimensional nanostructured materials. This advances the understanding of the intricate relationship between nanoscale strain patterns and their consequent optoelectronic properties.

Large area nanoscale patterning of functional materials using organosilicate ink based nanotransfer printing

This paper presents a versatile nanotransfer printing method for achieving large-area sub-micron patterns of functional materials. Organosilicate ink formulations combined with effective release layers have been shown to facilitate patterning of materials through the commonly used patterning approaches—lift off, physical etching and chemical etching. In this paper, we demonstrate that organosilicate ink formulations function as an effective resist owing to its superior physico-chemical stability whereas the release layers ensure clean removal of the resist post patterning. We successfully demonstrate patterning of sub-micron structures (800 nm feature sizes) of chromium metal through the lift off approach, silicon through reactive ion etching technique and silicon dioxide through wet chemical etching technique illustrating the versatility of the reported method. This patterning methodology represents a significant advancement in enabling nanostructure fabrication within resource-constrained laboratories. The approach requires nothing more than a master mold containing the desired structures, a spin coater, a low-temperature hotplate, and a desktop reactive ion etch tool.

Solid-state electrochemical oxidation with polyelectrolyte membrane stamps for micro-/nanoscale pattern formation on Au surfaces.

Nanoscale-patterned Au surfaces are promising for a wide range of applications from bio/chemical sensors to high-performance electrodes. However, pattern formation using conventional resist-based methods is complex, expensive, and environmentally unfriendly. Herein, we report a novel approach for pattern formation on Au surfaces using solid-state electrochemical treatment with polymer electrolyte membrane (PEM) stamps. During electrolysis, the patterned structure of the PEM stamp was transferred onto the Au surface to form micro- and nanoscale oxide patterns. X-ray analysis of the treated surface confirmed the formation of an oxide film on the Au surface, which was subsequently reduced to metallic Au after air exposure for several weeks. Although the pattern height decreased with air exposure, a patterned structure with a height of several hundred nanometers was maintained following oxide reduction. Reflectance spectroscopy revealed that the patterned Au surface exhibited sharp reflectance peaks, the intensities and positions of which strongly depended on the measurement angle, which are key characteristics of diffraction gratings. This fast and facile electrochemical treatment process is promising for the preparation of patterned Au surfaces that can be applied in optical gratings and localized surface plasmon resonance sensors.

Advances in Direct Optical Lithography of Nanomaterials

The precise assembly of nanomaterials is essential for integrating nanomaterials into sophisticated devices. However, the conventional nanoscale patterning methods face obstacles such as high-cost, low-resolution, and environmental contamination. Direct optical...

UV-assisted nanoimprint lithography: the impact of the loading effect in silicon on nanoscale patterns of metalens.

This work studies the impact of the silicon (Si) loading effect induced by deep reactive ion etching (DRIE) of silicon master molds on the UV-nanoimprint lithography (NIL) patterning of nanofeatures. The silicon molds were patterned with metasurface features with widths varying from 270 to 60 nm. This effect was studied by focus ion beam scanning electron microscopy (FIB-SEM) and atomic force microscopy (AFM). The Si loading etching effect is characterized by the variation of pattern feature depth concerning feature sizes because smaller features tend to etch more slowly than larger ones due to etchants being more difficult to pass through the smaller hole and byproducts being harder to diffuse out too. Thus, the NIL results obtained from the Si master mold contain different pattern geometries concerning pattern quality and residual photoresist layer thickness. The obtained results are pivotal for NIL for fabricating devices with various geometrical nanostructures as the research field moves towards commercial applications.

Rapid prototyping of etch test structures for hard mask development using electron beam lithography

Semiconductor manufacturing depends on the development of new processes, advanced patterning, and novel materials to create smaller and higher performing devices to follow the industry roadmaps for applications for computing and systems (such as smartphones and servers). For dynamic random access memory (DRAM) applications, the biggest efforts are engaged in scaling and shrinking of the nodes, and these then affect the area density, performance, and cost of the DRAM cells. However, while we are reaching a slowdown in dimension-scaling, more innovation is needed to sustain the high aspect ratios required in the capacitor’s architecture—whether it is moving toward 3D architectures or developing new materials to sustain the challenge of scaling. To accelerate the learning, it is essential to screen novel hard mask (HM) materials in a rapid fashion to speed their development. While EUV (extreme ultraviolet—a wavelength of 13.5 nm) lithography requires 300 mm wafers, electron beam lithography (EBL) generates nanoscale patterns in a maskless manner on smaller substrates (from 300 mm wafers to 10 mm2 coupons) mimicking sub-50 nm EUV features. The primary goal of this work is to create a path for rapid screening of HM materials that are still under early phase development and which are prepared in small chamber tools (coupon chambers) and, therefore, not ready for 300 mm process integration. While the features investigated of 44 nm half pitch seem extremely reasonable for e-beam, the requirements and the approaches used to address the needed patterned area, resolution, speed, and uniformity exceed the standard conditions previously reported in the literature. Each aspect will be evaluated in the context of a “dots on the fly,” or DOTF, patterning technique.

Low-cost and simple fabrication of micro-mask/micro-channels on different substrates based on water-soluble fiber poly (vinyl alcohol) (PVA)

Here we report an approach to fabricate micro-mask/micro-channels using water-soluble fiber poly (vinyl alcohol) (PVA). The scheme is a simple, environmentally friendly, and low-cost technology, that can realize the preparation of micro-mask/micro-channels on different substrates. Scanning electron microscope (SEM) and optical microscope (OM) are used to observe surface morphology and measured fiber diameter. We showed that a variety of micro-mask/micro-channels can be easily controlled by changing the swelling temperature and time of the PVA fiber. The swelling temperature was varied from 25 °C to 50 °C, the diameter of the fiber increased by 9.5 μm, and the diameter and volume swelling rates reached 59.38% and 154%, respectively. Meanwhile, with the increase in swelling time, the diameter and volume swelling rate showed the same increasing trend. Additionally, we used the PVA fiber as a micro-mask to prepare the micro-channel on the WSe2 surface and verified the feasibility of the PVA fiber to prepare micro-mask/micro-channels by testing the electrical properties of the WSe2 sample. Finally, we also verified the feasibility of the above methods to fabricate micro-mask/micro-channels on different substrates such as conductive fibers, PDMS, and WSe2/SiO2Si, and proposed to realize nano-scale patterning through direct electrospinning. Therefore, it is expected to be more widely promoted in the future.

Super-Resolution Analysis of the Origins of the Elementary Events of ER Calcium Release in Dorsal Root Ganglion Neurons.

Coordinated events of calcium (Ca2+) released from the endoplasmic reticulum (ER) are key second messengers in excitable cells. In pain-sensing dorsal root ganglion (DRG) neurons, these events can be observed as Ca2+ sparks, produced by a combination of ryanodine receptors (RyR) and inositol 1,4,5-triphosphate receptors (IP3R1). These microscopic signals offer the neuronal cells with a possible means of modulating the subplasmalemmal Ca2+ handling, initiating vesicular exocytosis. With super-resolution dSTORM and expansion microscopies, we visualised the nanoscale distributions of both RyR and IP3R1 that featured loosely organised clusters in the subplasmalemmal regions of cultured rat DRG somata. We adapted a novel correlative microscopy protocol to examine the nanoscale patterns of RyR and IP3R1 in the locality of each Ca2+ spark. We found that most subplasmalemmal sparks correlated with relatively small groups of RyR whilst larger sparks were often associated with larger groups of IP3R1. These data also showed spontaneous Ca2+ sparks in <30% of the subplasmalemmal cell area but consisted of both these channel species at a 3.8-5 times higher density than in nonactive regions of the cell. Taken together, these observations reveal distinct patterns and length scales of RyR and IP3R1 co-clustering at contact sites between the ER and the surface plasmalemma that encode the positions and the quantity of Ca2+ released at each Ca2+ spark.