RESUMEN

The directed self-assembly (DSA) of block copolymers (BCPs) is a promising next-generation lithography technique for high-resolution patterning. However, achieving lithographically applicable BCP organization such as out-of-plane lamellae requires proper tuning of interfacial energies between the BCP domains and the substrate, which remains difficult to address effectively and efficiently with high-χ BCPs. Here, we present the successful generation of anisotropic wetting by plasma treatment on patterned spin-on-carbon (SOC) substrates and its application to the DSA of a high-χ Si-containing material, poly(1,1-dimethylsilacyclobutane)-block-polystyrene (PDMSB-b-PS), with a 9 nm half pitch. Exposing the SOC substrate to different plasma chemistries promotes the vertical alignment of the PDMSB-b-PS lamellae within the trenches. In particular, a patterned substrate treated with HBr/O2 plasma gives both a neutral wetting at the bottom interface and a strong PS-affine wetting at the sidewalls of the SOC trenches to efficiently guide the vertical BCP lamellae. Furthermore, prolonged exposure to HBr/O2 plasma enables an adjustment of the trench width and an increased density of BCP lines on the substrate. Experimental observations are in agreement with a free energy configurational model developed to describe the system. These advances, which could be easily implemented in industry, could contribute to the wider adoption of self-assembly techniques in microelectronics, and beyond to applications such as metasurfaces, surface-enhanced Raman spectroscopy, and sensing technologies.

RESUMEN

Olfaction, a primal and effective sense, profoundly impacts our emotions and instincts. This sensory system plays a crucial role in detecting volatile organic compounds (VOCs) and realizing the chemical environment. Animals possess superior olfactory systems compared to humans. Thus, taking inspiration from nature, artificial olfaction aims to achieve a similar level of excellence in VOC detection. In this study, we present the development of an artificial olfaction sensor utilizing a nanostructured bio-field-effect transistor (bio-FET) based on transition metal dichalcogenides and the Drosophila odor-binding protein LUSH. To create an effective sensing platform, we prepared a hexagonal nanoporous structure of molybdenum disulfide (MoS2) using block copolymer lithography and selective etching techniques. This structure provides plenty of active sites for the integration of the LUSH protein, enabling enhanced binding with ethanol (EtOH) for detection purposes. The coupling of the biomolecule with EtOH influences the bio-FETs potential, which generates indicative electrical signals. By mimicking the sniffing techniques observed in Drosophila, these bio-FETs exhibit an impressive limit of detection of 10-6% for EtOH, with high selectivity, sensitivity, and detection ability even in realistic environments. This bioelectric sensor demonstrates substantial potential in the field of artificial olfaction, offering advancements in VOC detection.

Asunto(s)

Técnicas Biosensibles , Nanoporos , Compuestos Orgánicos Volátiles , Humanos , Animales , Drosophila , Molibdeno/química , Técnicas Biosensibles/métodos , Etanol , Órganos de los Sentidos

RESUMEN

Polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) is one of the most widely studied block copolymers for direct self-assembly because of its excellent compatibility with traditional processes. However, pattern transfer of PS-b-PMMA block copolymers (BCPs) remains a great challenge for its applications due to the insufficient etching resolution. In this study, the effect of ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate (HMHF) additives on the line edge roughness (LER) performances of PS-b-PMMA self-assembled patterns was studied. Trace addition of HMHF kept the photolithography compatibility of PS-b-PMMA block copolymer films, but obviously increased their Flory-Huggins interaction parameter (χ) and enabled phase separation of disordered low molecular weight BCPs. LER value was effectively decreased by blending HMHF directly with PS-b-PMMA or from a supplying top layer of polyvinylpyrrolidone containing HMHF additives. This study shows an excellent strategy to improve the deficiencies of existing block copolymers.

RESUMEN

Metalnanoparticles(NPs) can exhibit unique electronic, magnetic, optical, and catalytic properties. Highly ordered, dense arrays of non-close-packed, surface-supported metal NPs are thus of potential use in a wide range of applications. Implementing such arrays over large surfaces can, however, be both technologically challenging and prohibitively expensive using conventional top-down nanofabrication techniques. Moreover, many existing patterning methods are too harsh for sensitive substrate surfaces and their applications. To address this, we here investigate a fabrication protocol involving a water-based lift-off scheme in which the template pattern generation is rapidly and inexpensively achieved throughblock copolymer(BCP) self-assembly. A three-layer lift-off stack consisting of, from top to bottom, a poly(styrene-block-2-vinyl pyridine) template, a SiOxintermediate hardmask, and a water-soluble poly(vinyl alcohol) sacrificial layer is employed in this endeavor.Solvent-induced surface reconstruction(SISR) is used to generate an initial surface topography in the BCP template which is subsequently transferred to the layers beneath in a sequence of reactive ion etching steps. Through judicious selection of stack materials and dry etch chemistries, a layered, high-aspect-ratio, nanoporous mask is thus implemented. After metal deposition, the mask and excess material are simply removed in a lift-off step by dissolving the bottommost sacrificial layer in water. The incorporation of an intermediate hardmask and a water-soluble sacrificial layer obviates the need for harmful and/or corrosive lift-off solvents and decouples the BCP self-assembly process from the influence of substrate properties. We demonstrate the generation of well-ordered arrays of Au NPs capable of supporting sharp, localized surface plasmon resonances. We also investigate improvements to large-scale uniformity, as this is found sensitive to the SISR termination step in the original protocol. Extensions of the technique to other BCP morphologies and materials deposited ought to be straightforward.

RESUMEN

Although various two-dimensional (2D) materials hold great promise in next generation electronic devices, there are many challenges to overcome to be used in practical applications. One of them is the substrate effect, which directly affects the device performance. The large interfacial area and interaction between 2D materials and substrate significantly deteriorate the device performance. Several top-down approaches have been suggested to solve the problem. Unfortunately, however, they have some drawbacks such as a complicated fabrication process, a high production cost, or a poor mechanical property. Here, we suggest the partially suspended 2D materials-based field-effect transistors (FETs) by introducing block copolymer (BCP) lithography to fabricate the substrate effect-free 2D electronic devices. A wide range of nanometer size holes (diameter = 31~43 nm) is successfully realized with a BCP self-assembly nanopatterning process. With this approach, the interaction mechanism between active 2D materials and substrate is elucidated by precisely measuring the device performance at varied feature size. Our strategy can be widely applied to fabricate 2D materials-based high performance electronic, optoelectronic, and energy devices using a versatile self-assembly nanopatterning process.

RESUMEN

Electron states in semiconductor materials can be modified by quantum confinement. Adding to semiconductor heterostructures the concept of lateral geometry offers the possibility to further tailor the electronic band structure with the creation of unique flat bands. Using block copolymer lithography, we describe the design, fabrication, and characterization of multiorbital bands in a honeycomb In0.53Ga0.47As/InP heterostructure quantum well with a lattice constant of 21 nm. Thanks to an optimized surface quality, scanning tunnelling spectroscopy reveals the existence of a strong resonance localized between the lattice sites, signature of a p-orbital flat band. Together with theoretical computations, the impact of the nanopatterning imperfections on the band structure is examined. We show that the flat band is protected against the lateral and vertical disorder, making this industry-standard system particularly attractive for the study of exotic phases of matter.

RESUMEN

A surface-enhanced Raman spectroscopy sensing template consisting of gold-covered nanopillars is developed. The plasmonic slab consists of a perforated gold film at the base of the nanopillars and a Babinet complementary dot array on top of the pillars. The nanopillars were fabricated by the incorporation of an iron salt precursor into a self-assembled block copolymer thin film and subsequent reactive ion etching. The preparation is easy, scalable, and cost-effective. We report on the increase in surface-enhanced Raman scattering efficiency for smaller pillar heights and stronger coupling between the dot array and perforated gold film with average enhancement factors as high as 107. In addition, the block copolymer-derived templates show an excellent relative standard deviation of 8% in the measurement of the Raman intensity. Finite difference time domain simulations were performed to investigate the nature of the electromagnetic near-field enhancement and to identify plasmonic hot spots.

RESUMEN

Studies have demonstrated that the thermal conductivity (κ) of crystalline semiconductor materials can be reduced by phonon scattering in periodic nanostructures formed using templates fabricated from self-assembled block copolymers (BCPs). Compared to crystalline materials, the heat transport mechanisms in amorphous inorganic materials differ significantly and have been explored far less extensively. However, thermal management of amorphous inorganic solids is crucial for a broad range of semiconductor devices. Here we present the fabrication of freestanding amorphous silicon nitride (SiNx) membranes for studying κ in an amorphous solid. To form a periodic nanostructure, directed self-assembly of cylinder-forming BCPs is used to pattern in the SiNx highly ordered, hexagonally close packed nanopores with pitch and neck width down to 37.5 and 12 nm, respectively. The κ of the nanoporous SiNx membranes is 60% smaller than the classically predicted value based on just the membrane porosity. In comparison, holes with much larger neck widths and pitches patterned by e-beam lithography lead to only a slight reduction in κ, which is closer to the classical porosity-based prediction. These results demonstrate that κ of amorphous SiNx can be reduced by introducing periodic nanostructures that behave as a phononic crystal, where the relationship between the smallest dimension of the nanostructure and the length scale of the mean-free paths of the dominant, heat-carrying phonons is critical. Additionally, changing the orientation of the hexagonal array of nanopores relative to the primary direction of heat flow has a smaller impact on amorphous SiNx than was previously observed in silicon.

RESUMEN

Directed self-assembly (DSA) of block copolymers (BCPs) has long been viewed as a powerful alternative to extend the resolution of optical lithography. For full-area patterning applications, despite significant progress, the two most prominent DSA methods (chemoepitaxy and graphoepitaxy) are facing a scalability challenge: the critical dimension (CD) of the guiding patterns will need to be continuously scaled down to closely match the dimension of the BCP microdomain, a task that not only contravenes some of the resolution gains achieved by density multiplication but that will also become particularly difficult below 10 nm. To avoid this conundrum, we propose here a synergistic integration of graphoepitaxy and chemoepitaxy through self-registered self-assembly (SRSA) to enable the simultaneous realization of feature density multiplication and CD shrinkage resolution gains. We report nearly perfect DSA on prepatterns with high density multiplication factors and CD of several multiples of the BCP microdomain size. A prepattern consisting of alternating stripes of a relatively thicker neutral mat and a thinner neutral brush with preferential wetting sidewalls serves as a topographic pattern to guide an ultrathin BCP blend film inside the trenches. As the oriented BCP pattern assembles, the blend film deploys a layer of chemical markers on the bottom surface through SRSA generating 1:1 chemical contrast patterns inside the trenches. After thorough removal of the blend film, the newly formed self-registered chemical patterns interpolated by the remaining neutral mat strips serve as the guiding patterns for a second chemoepitaxial DSA step to achieve full-area, defect-free DSA of thick BCP films.

RESUMEN

The growing interest in solar energy during recent years has spurred on the development of high-efficiency optical absorbers using emerging concepts in plasmonics and metamaterials. Most absorber designs require patterning on a subwavelength scale, making large-scale fabrication expensive or impractical. This study presents an all-metal metasurface with tightly packed, sub-80 nm nanodomes fabricated by template-stripping thin gold films from reusable silicon templates. Subwavelength patterning was achieved via molecular self-assembly of block copolymers, which enables large-area, periodic patterning with nanometer precision. The proposed nanodome surface acts as an optical absorber capable of absorbing 97% of incident light in the visible range 320-650 nm, and still more than 90% at high incidence angles. We demonstrate both experimentally and theoretically that the absorption behavior of the thin film can be controlled by changing the size of the nanodomes, namely, the gap between the structures. The enhanced absorption of light is attributed to localized particle plasmon and gap plasmon resonances. This research provides a straightforward and cost-effective strategy to design and fabricate thin, large-area, light-absorbing coatings that can be transferred onto nearly any rigid or flexible substrate. The all-metal metasurfaces are a promising candidate for plasmon-induced hot electron generation for efficient solar energy conversion in photovoltaic and photocatalytic devices.

RESUMEN

In this study, a series of perpendicular lamellae-forming poly(polyhedral oligomeric silsesquioxane methacrylate-block-2,2,2-trifluoroethyl methacrylate)s (PMAPOSS-b-PTFEMAs) was developed based on the bottom-up concept of creating a simple yet effective material by tailoring the chemical properties and molecular composition of the material. The use of silicon (Si)-containing hybrid high-χ block copolymers (BCPs) provides easy access to sub-10 nm feature sizes. However, as the surface free energies (SFEs) of Si-containing polymers are typically vastly lower than organic polymers, this tends to result in the selective segregation of the inorganic block onto the air interface and increased difficulty in controlling the BCP orientation in thin films. Therefore, by balancing the SFEs between the organic and inorganic blocks through the use of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) on the organic block, a polymer with an SFE similar to Si-containing polymers, orientation control of the BCP domains in thin films becomes much simpler. Herein, perpendicularly oriented BCP thin films with a χeff value of 0.45 were fabricated using simple spin-coating and thermal annealing processes under ambient conditions. The thin films displayed a minimum domain size of L0 = 11 nm, as observed via atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, directed self-assembly (DSA) of the BCP on a topographically prepatterned substrate using the grapho-epitaxy method was used to successfully obtain perpendicularly oriented lamellae with a half pitch size of ca. 8 nm.

RESUMEN

We report a novel nanofabrication process via block copolymer lithography using solvent vapor annealing. The nanolithography process is facile and scalable, enabling fabrication of highly ordered periodic patterns over entire wafers as substrates for surface-enhanced Raman spectroscopy (SERS). Direct silicon etching with high aspect ratio templated by the block copolymer mask is realized without any intermediate layer or external precursors. Uniquely, an atomic layer deposition (ALD)-assisted method is introduced to allow reversing of the morphology relative to the initial pattern. As a result, highly ordered silicon nanopillar arrays are fabricated with controlled aspect ratios. After metallization, the resulting nanopillar arrays are suitable for SERS applications. These structures readily exhibit an average SERS enhancement factor of above 10(8), SERS uniformities of 8.5% relative standard deviation across 4 cm, and 6.5% relative standard deviation over 5 × 5 mm(2) surface area, as well as a very low SERS background. The as-prepared SERS substrate, with a good enhancement and large-area uniformity, is promising for practical SERS sensing applications.

RESUMEN

Templates of complex nanopatterns in a form of hierarchically sequenced dots and stripes can be generated in block copolymer films on lithography-free 3D topographic substrates. The approach exploits thickness- and swelling-responsive morphological behavior of block copolymers, and demonstrates novel possibilities of topography-guided registration of nanopatterns due to periodic confinement and spontaneous orthogonal flow-fields.

RESUMEN

We studied a type of nanostructured silicon photocathode for solar water splitting, where one-dimensionally periodic lamellar nanopatterns derived from the self-assembly of symmetric poly(styrene-block-methyl methacrylate) block copolymers were incorporated on the surface of single-crystalline silicon in configurations with and without a buried metallurgical junction. The resulting nanostructured silicon photocathodes with the characteristic lamellar morphology provided suppressed front-surface reflection and increased surface area, which collectively contributed to the enhanced photocatalytic performance in the hydrogen evolution reaction. The augmented light absorption in the nanostructured silicon directly translated to the increase of the saturation current density, while the onset potential decreased with the etching depth because of the increased levels of surface recombination. The pp(+)-silicon photocathodes, compared to the n(+)pp(+)-silicon with a buried solid-state junction, exhibited a more pronounced shift of the current density-potential curves upon the introduction of the nanostructured surface owing to the corresponding increase in the liquid/silicon junction area. Systematic studies on the morphology, optical properties, and photoelectrochemical characteristics of nanostructured silicon photocathodes, in conjunction with optical modeling based on the finite-difference time-domain method, provide quantitative description and optimal design rules of lamellar-patterned silicon photocathodes for solar water splitting.

RESUMEN

Here we describe a general method for synthesizing multimetallic core-shell nanoclusters on surfaces. By patterning seeds at predesignated locations using scanning-probe block copolymer lithography, we can track shape evolution in nanoclusters and elucidate their growth pathways using electron microscopy. The growth of core-shell nanostructures on surface-bound seeds is a highly anisotropic process and often results in multimetallic anisotropic nanostructures. The shell grows at specific edge and corner sites of the patterned seeds and propagates predominately from the top hemisphere of the seeds.

RESUMEN

We explore the lithographic limits of lamellae-forming PS-b-PMMA block copolymers by performing directed self-assembly and pattern transfer on a range of PS-b-PMMA materials having a full pitch from 27 to 18.5 nm. While directed self-assembly on chemical contrast patterns was successful with all the materials used in this study, clean removal of PMMA domains and subsequent pattern transfer could only be sustained down to 22 nm full pitch. We attribute this limitation to the width of the interface, which may represent more than half of the domain width for materials with a critical dimension below 10 nm. With the limit of pattern transfer for PS-b-PMMA set at ∼11 nm, we propose an integration scheme suitable for bit patterned media for densities above 1.6 Tdot/in(2), which require features below this limit. Directed self-assembly was carried out on chemical contrast patterns made by a rotary e-beam lithography system, and pattern transfer was carried out to demonstrate fabrication of large area (up to 25 mm-wide annular band of circular tracks) nanoimprint templates for bit patterned media. We also demonstrate compatibility with hard disk drive architecture by fabricating patterns with skewed radial lines with constant angular pitch and with servo patterns that are needed in hard disk drives to generate a radial positional error signal (PES).

RESUMEN

While block copolymer lithography has been broadly applied as a bottom-up patterning technique, only a few nanopattern symmetries, such as hexagonally packed dots or parallel stripes, can be produced by spontaneous self-assembly of simple diblock copolymers; even a simple square packing has heretofore required more intricate macromolecular architectures or nanoscale substrate prepatterning. In this study, we demonstrate that square, rectangular, and rhombic arrays can be created via shear-alignment of distinct layers of cylinder-forming block copolymers, coupled with cross-linking of the layers using ultraviolet light. Furthermore, these block copolymer arrays can in turn be used as templates to fabricate dense, substrate-supported arrays of nanostructures comprising a wide variety of elements: deep (>50 nm) nanowells, nanoposts, and thin metal nanodots (3 nm thick, 35 nm pitch) are all demonstrated.

RESUMEN

Alignment of perpendicularly oriented lamellar block copolymer domains using an AFM tip is demonstrated. The AFM tip orients the domains through local shearing, resulting in domain alignment parallel to tip travel. AFM tips can also deposit block copolymer nanostructures on heated substrates with a variety of experimentally observed domain alignments.

RESUMEN

Highly selective etch masks are formed by thin films of a polystyrene-b-poly(ferrocenylisopropylmethylsilane) diblock copolymer, PS-PFiPMS, containing hemicylindrical domains of PFiPMS. These domains, with a period of 35 nm, are readily aligned through mechanical shear. Aligned PS-PFiPMS templates are employed to fabricate high-aspect-ratio nanowire grids from amorphous silicon, which can polarize deep ultraviolet radiation, including 193 nm, at >90% efficiency.

RESUMEN

Robust, large area, superhydrophobic surfaces with feature sizes approaching 10 nm are fabricated by block-copolymer-based thin-film patterning. We show that tuning the nanostructure shape and aspect ratio dramatically influences the surface wetting properties, with proper control crucial for achieving superhydrophobicity.