A study of virtual lithography process for polymer directed self-assembly

For the feature size scaling down to tens of nanometers, the top-down approaches are getting more severe because the extremely ultra-violet (EUV) technique, the high-index fluid-based immersion ArF lithography, and the double patterning technology (DPT) under development may be cover one or two generations. An alternative technology to extend lithography patterning beyond current resolution limits is to combine the top-down lithography and bottom-up assembly.In this paper, an directed self-assembly lithography process of “bottom-up” block copolymer self-assembly, is modeled and simulated in molecular-scale. Impacts of block polymer components on pattern formation are analyzed and discussed.     

High-performance and stability bifacial flexible self-powered perovskite photodetector by surface plasmon resonance and hydrophobic treatments

Flexible semitransparent photodetectors based on perovskites provide merits in terms of light weight and bifacial advantages but suffer from poor stability. To simultaneously enhance the performance and stability of flexible perovskite photodetectors (PPDs), silver (Ag) nanoparticles are incorporated to improve the responsiveness through the surface plasmon resonance (SPR) effect in the bulk of perovskite layer, and block copolymer F68 is employed to increase the surface hydrophobicity of perovskite film to keep long-term stable devices. Ag@polyvinyl pyrrolidone (PVP) core shell structure enables the sufficiently enhanced film light absorption and device quantum efficiency following the SPR response curve, the amphiphilic F68 make the perovskite less vulnerable to humid ambient exposure. Moreover, the sputtered transparent indium tin oxide back electrode enables the double facial operability of our flexible self-powered photodetectors with a bifacial factor of 80% and improved stability as well. Addressing the poor responsiveness and instability issues extends the potential broad applications of our bifacial flexible perovskite photodetectors.     

Block Copolymer Surface Reconstuction: A Reversible Route to Nanoporous Films

Thin films of block copolymers have been used as templates and scaffolds for the fabrication of arrays of nanostructured materials. In general, a chemical modification of the film or the removal of one of the components by photodegradative methods is required to produce a nanoporous film that serves as a template or scaffold. Here, however, the preferential interaction of one of the components with a solvent is shown to produce a reconstruction of the block copolymer film that, upon drying, leads to the generation of a nanoporous template. The area density of the pores is identical to that of the original copolymer thin film. Since no chemical reactions occurr, the process is fully reversible. Upon heating the copolymer film above its glass‐transition temperature, mobility is imparted to the copolymer and the original copolymer film with oriented domains is recovered. The film reconstruction significantly simplifies the generation of nanoporous templates.     

Processable High Electron Mobility π-Copolymers via Mesoscale Backbone Conformational Ordering

The synthesis and experimental/theoretical characterization of a new series of electron-transporting copolymers based on the naphthalene bis(4,8-diamino-1,5-dicarboxyl)amide (NBA) building block are reported. Comonomers are designed to test the emergent effects of manipulating backbone torsional characteristics, and density functional theory (DFT) analysis reveals the key role of backbone conformation in optimizing electronic delocalization and transport. The NBA copolymer conformational and electronic properties are characterized using a broad array of molecular/macromolecular, thermal, optical, electrochemical, and charge transport techniques. All NBA copolymers exhibit strongly aggregated morphologies with significant nanoscale order. Copolymer charge transport properties are investigated in thin-film transistors and exhibit excellent electron mobilities ranging from 0.4 to 4.5 cm² V⁻¹ s⁻¹. Importantly, the electron transport efficiency correlates with the film mesoscale order, which emerges from comonomer-dependent backbone planarity and extension. These results illuminate the key NBA building block structure–morphology–bulk property design relationships essential for processable, electronics-applicable high-performance polymeric semiconductors.     

3D Nanostructured Conjugated Polymers for Optical Applications

The self assembly of block‐copolymers into the gyroid morphology is replicated into 3D nanostructured conjugated polymers. Voided styrenic gyroidal networks are used as scaffolds for the electrodeposition of two poly(3,4‐ethylenedioxythiophene) derivatives and poly(pyrrole). The careful choice of solvents and electrolytes allows the excellent replication of the initial self‐assembled morphology into self‐supporting gyroidal conjugated polymer networks. The nanostructured films are employed to fabricate electrochromic devices, exhibiting excellent color contrast upon switching, with fast switching speeds. The versatility and reliability of this method are demonstrated by the creation of switchable Fresnel zone plates, with which the focussing of light can be switched on and off.     

Virus Filtration Membranes Prepared from Nanoporous Block Copolymers with Good Dimensional Stability under High Pressures and Excellent Solvent Resistance

We introduce a nanoporous membrane suitable for virus filtration with good dimensional stability under high pressures maintaining high selectivity. The membrane consists of a double layer: The upper layer is a nanoporous film with pore size of ～17 nm and a thickness of ～160 nm, which was prepared by polystyrene‐block‐poly(methyl methacrylate) copolymer (PS‐b‐PMMA) where PMMA block was removed by ultraviolet irradiation followed by rinsing with acetic acid. The nanoporous block copolymer film was combined with a conventional micro‐filtration membrane to enhance mechanical strength. The membrane employed in this study did not show any damage or crack even at a pressure of 2 bar, while high selectivity was maintained for the filtration of human rhinovirus type 14 which has a diameter of ～30 nm and is a major pathogen of the common cold in humans. Furthermore, due to crosslinked PS matrix during the UV irradiation, the nanoporous membrane showed excellent resistance to all organic solvents. This could be used under harsh filtration conditions such as high temperature and strong acidic (or basic) solution.     

Widely Tunable Morphologies in Block Copolymer Thin Films Through Solvent Vapor Annealing Using Mixtures of Selective Solvents

Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymer de novo within the corresponding volume ratio of the blocks. In this work, solvent vapor annealing in supported thin films of poly(2‐hydroxyethyl methacrylate)‐block‐poly(methyl methacrylate) [PHEMA‐b‐PMMA] by means of grazing incidence small angle X‐ray scattering (GISAXS) is investigated. A spin‐coated thin film of a lamellar block copolymer is solvent vapor annealed to induce microphase separation and improve the long‐range order of the self‐assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents, which are chosen to be preferential for each block, enables selective formation of ordered lamellae, gyroid, hexagonal, or spherical morphologies from a single‐block copolymer with a fixed volume fraction. The selected microstructure is then kinetically trapped in the dry film by rapid drying. This paper describes what is thought to be the first reported case where in situ methods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram.     

Thermally Switched Release from Nanoparticle Colloidosomes

Nanoparticle colloidosomes, whose release can be switched on and off in response to a temperature change, are fabricated. Unlike in other systems, the switchable release does not require the colloidosome shell to deform; it instead occurs due to the adsorption or desorption of a block copolymer, dissolved in the core, at the inner surface of the colloidosome shell, concomitantly blocking or unblocking the pores in the shell. The colloidosomes are prepared using double emulsion templates produced by microfluidics, and are thus highly monodisperse; moreover, they are mechanically stable and consist of biocompatible components, making them suitable for the encapsulation, delivery, and release of a broad range of active materials.     

DSA guiding template assignment with multiple redundant via and dummy via insertion

As an emerging manufacture technology, block copolymer directed self-assembly (DSA) is promising for via layer fabrication. Meanwhile, redundant via insertion is considered as an essential step for yield improvement. For better reliability and manufacturability, in this paper, we first concurrently consider DSA guiding template cost assignment with multiple redundant via and dummy via insertion. Firstly, by analyzing the structure property of guiding templates, we propose a building-block based solution expression to discard redundant solutions. Then, honoring the compact solution expression, we construct a conflict graph with dummy via insertion, and then formulate the problem to an integer linear programming (ILP). In addition, to optimize the guiding template cost, we incorporate it into the objective of ILP by introducing vertex weight and edge weight in conflict graph. To make a good trade-off between solution quality and runtime, we relax the ILP to an unconstrained nonlinear programming (UNP). Finally, a line search optimization algorithm is proposed to solve the UNP. Experimental results verify the effectiveness of our new solution expression and the efficiency of our proposed algorithm. Specifically, our guiding template cost optimization method can save 18% total guiding template cost.     

Profile Control in Block Copolymer Nanostructures using Bilayer Thin Films for Enhanced Pattern Transfer Processes

Although control over the domain orientation and long‐range order of block copolymer nanostructures self‐assembled in thin films has been achieved using various directed self‐assembly techniques, more challenging but equally important for many lithographic applications is the ability to precisely control the shape of the interface between domains. Here, a novel layer‐by‐layer approach is reported for controlling the interface profile of block copolymer nanostructures and the application of an undercut sidewall profile for an enhanced metal lift‐off process for pattern transfer is demonstrated. Bilayer films of lamellar‐forming poly(styrene‐block‐methyl methacrylate) are assembled and thermally cross‐linked on wafer substrates in a layer‐by‐layer process. The top layer, while being directed to self‐assemble on the lamellae of the underlying layer, has a tunable composition and polystyrene domain width independent of that of the bottom layer. Undercut or negative sidewall profiles in the PS nanostructures are proven to provide better templates for the lift‐off of Au nanowires by achieving complete and defect‐free pattern transfer more than three times faster than comparable systems with vertical sidewall profiles. More broadly, the layer‐by‐layer approach presented here provides a pathway to achieving sophisticated interface profiles and user‐defined 3D block copolymer nanostructures in thin films.     

J-Aggregation-Driven Supramolecular Assembly of Dye-Conjugated Block Polymers: From Morphological Tailoring to Anticancer Applications

Utilizing the J-stacking of dyes to drive the assembly of amphiphilic polymers can not only construct supramolecular assemblies with novel architectures but also provide a stabilizing solution for dye J-aggregation to promote its biomedical applications. However, tightly entangled hydrophobic segments can disrupt the orderly arrangement of dye molecules, thereby preventing dye stacking-driven supramolecular assembly of block copolymers. Herein, a “molecular glue” strategy is reported that uses the small dye molecule as a molecular glue to restore the J-stacking of the dye moiety immobilized on the polymer, thereby dominating the supramolecular assembly of the polymer matrix. Very interestingly, the yielded nano-assembly exhibits a novel worm-like structure with alternating straight and bent segments. By passing through nanopores, the bent part is disassembled to afford short nanorod NR-J812 mainly composed of crystalline dye J-aggregates. It shows favorable colloidal and optical stability, suitable size, and high photothermal property, and demonstrates high performance in photoacoustic imaging and photothermal treatment of tumors in vivo. This work provides important insights into not only the self-assembly of amphiphilic polymers with novel supramolecular architectures but also the preparation of J-aggregate materials applicable in vivo, which bring great promise to the biomedical fields.     

A Step‐Wise Approach for Dual Nanoparticle Patterning via Block Copolymer Self‐Assembly

A novel step‐wise approach for fabrication of periodic arrays of two different types of nanoparticles (NPs), selectively localized at different block copolymer phases is demonstrated. In the first step, pre‐synthesized ≈12 nm silver nanoparticles (AgNPs), stabilized with thiol‐terminated polystyrene, are mixed with poly(styrene‐block‐vinylpyridine) (PS‐b‐PVP) block copolymer in a common solvent. After film casting and consequent solvent vapor annealing the AgNPs are selectively localized within the PS phase of the block copolymer matrix due to the interaction with PS shell of the nanoparticles. In the second step, ≈2–5 nm gold, platinum, or palladium nanoparticles are directly deposited from their aqueous dispersion on the PVP domains of the self‐assembled block copolymer thin films. In such a way, thin films of nanostructured block copolymer with two types of nanoparticles, separated by the two distinct block copolymer phases, are prepared in a step‐wise manner. The presented method is very simple and can be applied for various combinations of pre‐synthesized nanoparticles where the characteristics of either type of nanoparticles are tuned accordingly in advance, which is more difficult to achieve for in situ synthesized nanoparticles.     

Electrochemically Triggered Selective Adsorption of Biotemplated Nanoparticles on Self‐Assembled Organometallic Diblock Copolymer Thin Films

The controlled adsorption of the iron‐containing cage protein ferritin at the nanoscale using stimuli‐responsive self‐assembled diblock copolymer thin‐film templates is reported. The diblock copolymer used study consists of a cylinder‐forming polystyrene‐block‐polyferrocenylsilane (PS‐b‐PFS), with PFS as the minor block, and shows reversible redox properties. To prevent any spontaneous protein adsorption on either block, the electrolyte pH is selected to leave the ferritin negatively charged, and the protein concentration and solution ionic strength are carefully tuned. Selective adsorption of ferritin on the PFS domains of the self‐assembled thin films is then triggered in situ by applying a positive potential, simultaneously oxidizing the PFS and attracting the ferritin electrostatically.     

Block copolymers as photonic bandgap materials

Block copolymers self-assemble into one-, two-, and three-dimensional periodic equilibrium structures, which can exhibit photonic bandgaps. This paper outlines a methodology for producing photonic crystals at optical length scales from block copolymers. Techniques for enhancing the intrinsic dielectric contrast between the block copolymer domains, as well as increasing the characteristic microdomain distances, and controlling defects are presented. To demonstrate the applicability of this methodology, a self-assembled one-dimensional periodic structure has been fabricated that reflects visible light. The wealth of structures into which block copolymers can assemble and the multiple degrees of freedom that can be built into these materials on the molecular level offer a large parameter space for tailoring new types of photonic crystals at optical length scales     

艾里高斯涡旋光束正负交变介质中的光波演变

利用光学传输矩阵,结合广义惠更斯-菲涅耳光学衍射公式,研究了艾里高斯涡旋光束在正负折射率交替变化周期平板介质中传输时,其输出横截面光强分布规律和侧面传输光强的演变图景。结论显示:当右手材料折射率nr和双负材料折射率nl绝对值正好相等,并且右手单元长度R:双负单元长度L=1:1时,可以实现输出面光强的完美还原;当双负材料折射率绝对值abs（nl）nr,但R=L时,两类周期介质输出表面的光束质量都很差,此时,若要实现输出光强的完美还原,较大的abs（nl）需要较长的双负单元长度L来进行补偿,反之则反;进一步探究了准周期平板介质中双负材料单元长度和负折射率的定量关系。期望相关结论可以对含特异材质周期和准周期结构中艾里高斯涡旋光束的调控和通信传输提供重要的参考价值。     

FPGA architecture of the LDPS Motion Estimation for H.264/AVC Video Coding

Motion estimation is a highly computational demanding operation during video compression process and significantly affects the output quality of an encoded sequence. Special hardware architectures are required to achieve real-time compression performance. Many fast search block matching motion estimation (BMME) algorithms have been developed in order to minimize search positions and speed up computation but they do not take into account how they can be effectively implemented by hardware. In this paper, we propose three new hardware architectures of fast search block matching motion estimation algorithm using Line Diamond Parallel Search (LDPS) for H.264/AVC video coding system. These architectures use pipeline and parallel processing techniques and present minimum latency, maximum throughput and full utilization of hardware resources. The VHDL code has been tested and can work at high frequency in a Xilinx Virtex-5 FPGA circuit for the three proposed architectures.     

Get the lead out! [lead free solder]

Concern over lead's toxicity launched a quest for alternatives to the tin-lead solder common in printed-circuit board manufacture. The options for no-lead solders rely on tin as the base metal with smaller amounts of other metals, such as antimony, bismuth, copper, indium, silver, or zinc, added to enhance performance. Tin, which is considered to be one of the least toxic metals, will most probably endure as the base metal since it is relatively inexpensive, sufficiently available, and possesses desirable physical properties. In considering alternatives, the cost and availability of metals also come into play. Indeed, the limited availability and high costs of indium, bismuth, and silver-based alloy systems will likely prevent their widespread use. In 1997, a tin-copper alloy was used to assemble a desktop telephone, the first such product made with lead-free solder     

Genetically Modifiable Flagella as Templates for Silica Fibers: From Hybrid Nanotubes to 1D Periodic Nanohole Arrays

Bacterial flagellum is a protein nanotube that is helically self‐assembled from thousands of a protein subunit called flagellin. The solvent‐exposed domain of each flagellin on the flagella is genetically modifiable, in that a foreign peptide can be genetically inserted into this domain, leading to the high‐density display of this foreign peptide on the surface of flagella. In this work, wild‐type and genetically engineered flagella (inner diameter of ～2 nm and outer diameter of ～14 nm) detached from the surface of Salmonella bacterial cells are used as templates to site‐specifically form silica sheaths on the flagellar surface, resulting in the formation of double‐layered silica/flagella nanotubes. The flagella templates inside the silica/flagella nanotubes can be removed to obtain silica nanotubes by calcining the nanotubes at high temperature (550°C). Further calcination of the silica nanotubes at a higher temperature (800 °C) leads to the formation of a periodic nanohole array along the silica fibers with a center‐to‐center nanohole spacing of ～79 nm. It is demonstrated that the double‐layered silica‐flagella nanotubes can be used for selective CdTe quantum dot uptake into the inner channels or selective Au nanoparticle coating on the outer wall of the nanotubes due to the different chemistry between inner flagellum core (protein) and outer silica wall of the nanotubes. It is also found that flagella displaying different peptides result in different morphologies of the silica nanotubes. This work suggests that the monodisperse diameter and genetically tunable surface chemistry of the flagella can be exploited for the fabrication of silica nanotubes with uniform diameter and controllable morphologies as well as silica nanofibers decorated with periodic nanohole arrays.     

Double pocket architecture using indium and boron for sub-100 nmMOSFETs

A double pocket architecture for sub-100 nm MOSFET's is proposed on the basis of indium pocket profiling at higher dose than the amorphization threshold. At high dose, the low-energy indium pockets realize the improvement of short channel effects and shallow extension formation of a highly doped drain, maintaining the low junction leakage level. A double pocket architecture using indium and boron is demonstrated in a 70 nm gate length MOSFET with high drive currents and good control of the short channel effects     

Densely Packed Arrays of Ultra‐High‐Aspect‐Ratio Silicon Nanowires Fabricated using Block‐Copolymer Lithography and Metal‐Assisted Etching

Metal‐assisted etching is used in conjunction with block‐copolymer lithography to create ordered and densely‐packed arrays of high‐aspect‐ratio single‐crystal silicon nanowires with uniform crystallographic orientations. Nanowires with diameters and spacings down to 19 nm and 10 nm, respectively, are created as either continuous carpets or as carpets within trenches. Wires with aspect ratios up to 220 are fabricated, and capillary‐induced clustering of wires is eliminated through post‐etching critical point drying. The wires are single crystals with 〈100〉 axis directions. The distribution of wire diameters is narrow and closely follows the size distribution of the block copolymer, with a standard deviation of 3.12 nm for wires of mean diameters 22.06 nm. Wire arrays formed in carpets and in channels have hexagonal order with good fidelity to the block copolymer pattern. Fabrication of wires in topographic features demonstrates the ability to accurately control wire placement. Wire arrays made using this new process will have applications in the creation of arrays of photonic and sensing devices.