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1.
Mao W  Wathuthanthri I  Choi CH 《Optics letters》2011,36(16):3176-3178
We have designed and analyzed a novel (to the best of our knowledge) two-beam interference lithography system for large-area (wafer-level) nanopatterning with enhanced tunability of pattern periodicities. The tunable feature has been achieved by placing two rotational mirrors in the expanded beam paths at regulated angles for a desired period. Theoretical analyses show that the effective pattern coverage area greater than a 4 in. (10 cm) wafer scale is attainable with a 325 nm (30 cm coherence length) HeCd laser and 4 in. (10 cm) mirrors, while the pattern coverage area is restrained by the overruling effects between the optical coherence and mirror size. The experimental results also demonstrate uniform nanopatterns at varying periods (250-750 nm) on 4 in. (10 cm) substrates, validating the theoretical analyses. The tunable two-mirror interferometer will offer a convenient and robust way to prepare large-area nanostructures on a wafer scale with superior tunability in their pattern periodicities.  相似文献   

2.
Standard positive photoresist techniques were adapted to generate sub-micron scale patterns of gold substrate using self-assembled monolayers (SAMs) and femtosecond laser. Self-assembled monolayers formed by the adsorption of alkanethiols onto gold substrate are employed as very thin photoresists. The process underlying photopatterning of SAMs on gold is well-known at the phenomenological level. Alkanethiolates formed by the adsorption of alkanethiols are oxidized on exposure to UV light in the presence of air to alkylsulfonates. Specifically, it is known that deep UV light of wavelength less than 200 nm is necessary for oxidation to occur. In this study, solid state femtosecond laser of wavelength 800 nm is applied for photolithography. The results show that ultrafast laser of near infrared (NIR) range wavelength can replace deep UV laser source for photopatterning using thin organic films. The essential basis of our approach is the photochemical excitation of specific reactions in a particular functional group (in this case a thiolate sulfur atom) distributed with monolayer coverage on a solid surface. Femtosecond laser photolithography could be applied to fabricate the patterning of surface chemical structure and the creation of three-dimensional nanostructures by combination with suitable etching methods.  相似文献   

3.
This study presents the wetting properties, including hydrophilicity, hydrophobicity and anisotropic behavior, of water droplets on the silicon wafer surface with periodical nanopatterns and hierarchical structures. This study fabricates one- and two-dimensional periodical nanopatterns using laser interference lithography (LIL). The fabrication of hierarchical structures was effectively achieved by combining photolithography and LIL techniques. Unlike conventional fabrication methods, the LIL technique is mainly used to control the large-area design of periodical nanopatterns in this study. The minimum feature size for each nanopattern is 100 nm. This study shows that the wetting behavior of one-dimensional, two-dimensional, and hierarchical patterns can be obtained, benefiting the development of surface engineering for microfluidic systems.  相似文献   

4.
A simple and efficient principle for nanopatterning with wide applicability in the sub‐50 nanometer regime is chemisorption of nanoparticles; at homogeneous substrates, particles carrying surface charge may spontaneously self‐organize due to the electrostatic repulsion between adjacent particles. Guided by this principle, a method is presented to design, self‐assemble, and chemically functionalize gradient nanopatterns where the size of molecular domains can be tuned to match the level corresponding to single protein binding events. To modulate the binding of negatively charged gold nanoparticles both locally (<100 nm) and globally (>100 μm) onto a single modified gold substrate, ion diffusion is used to achieve spatial control of the particles’ mutual electrostatic interactions. By subsequent tailoring of different molecules to surface‐immobilized particles and the void areas surrounding them, nanopatterns are obtained with variable chemical domains along the gradient surface. Fimbriated Escherichia coli bacteria are bound to gradient nanopatterns with similar molecular composition and macroscopic contact angle, but different sizes of nanoscopic presentation of adhesive (hydrophobic) and repellent poly(ethylene) glycol (PEG) domains. It is shown that small hydrophobic domains, similar in size to the diameter of the bacterial fimbriae, supported firmly attached bacteria resembling catch‐bond binding, whereas a high number of loosely adhered bacteria are observed on larger hydrophobic domains.  相似文献   

5.
We applied spatially resolved photoelectron spectroscopy implemented with an X-ray photoemission electron microscopy (XPEEM) using soft X-ray synchrotron radiation to identify the compositional and morphological inhomogeneities of a SiO2/Si substrate surface nanopatterned with Al before and after nitridation. The nanofabrication was conducted by a polymethylmethacrylate (PMMA)-based e-beam lithography and a fluorine-based reactive ion etching (RIE), followed by Al metalization and acetone lift-off. Three types of chemical residues were identified before nitridation: (1) fluorocarbons produced and accumulated mainly during RIE process on the sidewalls of the nanopatterns; (2) a thick Al-bearing PMMA layer and/or (3) a thin PMMA residue layer owing to unsuccessful or partial lift-off of the e-beam unexposed PMMA between the nanopatterns. The fluorocarbons actively influenced the surface chemical composition of the nanopatterns by forming AlF compounds. After nitridation, in the PMMA residue-free area, the AlF compounds on the sidewalls were decomposed and transformed to AlN. The PMMA residues between the nanopatterns had no obvious influence on the surface chemical composition and nitridation properties of the Al nanopatterns. They were only partially decomposed by the nitridation. The regional surface morphology of the nanopatterns revealed by the secondary electron XPEEM was consistent with the scanning electron microscopy results.  相似文献   

6.
Self-Assembled Monolayers (SAMs) were prepared from mercapto-ended azobenzene derivatives with the structure of n-CnH2n+1, AzoO(CH2)mSH (n=4,6,8,10,12; m=3,5). the structure of these SAMs was thoroughly studied with grazing-angle incident reflection absorption FT1R technique and wettability measurement. the results suggested that the plane of Azobenzene system of the assembling molecules in the SAMs lies on its back with an approximate angle of 22° included between the substrate surface normal and the Azobenzene plane. Tail alkyl groups (n-CnH2n+1) in these assembling molecules were considered to be in an all-trans conformation, as if they were in a crystalline-like environment. and the C-C-C plane of these all-trans tail alkyl groups, while n≤8, lies also on its back with an angle about 70° between its plane and the substrate surface normal. the conformation of these head groups (-O(CH2)mSH) in SAMs are disturbed by many structural factors. While m=3 or 5, the head group chain was proposed to remain in a gauche conformation to fit the upright orientation of the Azobenzene plane. the packing density was investigated by measuring the contact angle of water on these SAMs. the results showed that the self-assembled monolayer films are perfectly packed and the coverage density might be improved with increasing the length of both tail and head alkyl chains.  相似文献   

7.
Self-assembled multilayers (SAMs) of poly (amide amine) generation 4.0 dendrimer, coded as the PAMAM G4.0 SAMs, were prepared successfully via a simple approach. The resulting SAMs were characterized by means of ellipsometry, contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy. Their micro-tribological behavior was evaluated using a reciprocal ball-on-disc test rig, while their nano-tribological behavior was evaluated using an atomic force microscope. Results of ellipsometry indicate that the thickness of the PAMAM G4.0 SAMs increased with increasing deposition time, which corresponds well to the enhanced intramolecular hydrogen bonding of the PAMAM as evidenced by the corresponding X-ray photoelectron spectroscope data. The thickness of the PAMAM G4.0 SAMs is an important factor affecting their tribological properties. The long wear-life in a micro-tribotest can be attributed to the interior cavities and flexible carbon chain of the PAMAM molecules.  相似文献   

8.
The problems caused by the adhesive force and friction force become more critical when the size of M/NEMS devices shrinks to micro/nano-scale. The nanotexture-patterned surface is an effective approach to reduce friction force on micro/nano-scale. Laser interference lithography is an attractive method to fabricate micro/nanotextures, which is maskless and allows large area periodical structures to be patterned by a couple of seconds’ exposure in a simple equipment system. We fabricate various nanogrooves with different pitch and space width on silicon wafers by laser interference lithography and chemical etching. We investigate the nanotribological properties of the patterned surfaces by AFM/FFM. We show that friction on the nano/micro-scale is related to the coverage rate of the nanogrooves, which decreases with increase in the space width and decrease in the pitch.  相似文献   

9.
We report the formation of highly robust long-chained alkylsiloxane self-assembled monolayers (SAMs) on aluminum oxide films prepared by atomic-layer deposition (ALD). The surface chemistry and the morphological characteristics of the SAMs were examined by X-ray photoelectron spectroscopy, infrared spectroscopy, atomic-force microscopy, and contact-angle goniometry. The octadecylsiloxane-derived SAMs initially hydrolyze and deposit on the alumina surface as ∼1.8 nm thick, monolayer-high islands ≤50 nm in diameter. The size of these islands increases with time, likely through a surface-diffusion aggregation process. Coalescence of neighboring islands leads to a densely packed and robust monolayer on the alumina surface. The SAMs on ALD alumina are expected to be useful in a number of nanostructure applications where the combination of conformal alumina deposition and conformal coverage of the alumina by an organic layer is critical. PACS 81.16.Dn; 81.65.Kn; 82.45.Mp; 81.65.-b  相似文献   

10.
Ian Thom 《Surface science》2005,581(1):33-46
The reductive desorption of self-assembled monolayers (SAMs) of ω-(4′-methyl-biphenyl-4-yl)-alkanethiols (CH3-C6H4-C6H4-(CH2)n-SH, BPn) on Au(1 1 1) on mica was studied in 0.5 M KOH solution as a function of the length of the aliphatic spacer chain (n = 1-6 and 12) and for two different preparations temperatures (295 K and 343 K). Second harmonic generation (SHG) was applied in situ parallel to cyclic voltammetry (CV). Odd-even differences in the structure of the BPn monolayers are clearly reflected in the electrochemical stability, as well as by the charge and shape of the desorption peak. For n = 1-5 a single desorption peak is detected whereas multiple peaks occur for BP6 similar to hexadecane thiol which was also studied for comparison. An increased preparation temperature affects the shape and width of the desorption peak but not the position. BP1 exhibits a temperature dependence different from the other homologues. The relationship between coverage monitored by SHG and desorption charge determined from the CVs is found to be linear and surprisingly independent from the details of the SAMs. The combined SHG and CV experiments suggest that capacitive and faradaic current are always closely coupled even for BP6 and hexadecane thiol which exhibit multiple desorption peaks.  相似文献   

11.
Fabricating of metal foams with desired morphological parameters including pore size, porosity and pore opening is possible now using sintering technology. Thus, if it is possible to determine the morphology of metal foam to absorb sound at a given frequency, and then fabricate it through sintering, it is expected to have optimized metal foams for the best sound absorption. Theoretical sound absorption models such as Lu model describe the relationship between morphological parameters and the sound absorption coefficient. In this study, the Lu model was used to optimize the morphological parameters of Aluminum metal foam for the best sound absorption coefficient. For this purpose, the Lu model was numerically solved using written codes in MATLAB software. After validating the proposed codes with benchmark data, the genetic algorithm (GA) was applied to optimize the affecting morphological parameters on the sound absorption coefficient. The optimization was carried out for the thicknesses of 5 mm to 40 mm at the sound frequency range of 250 Hz–8000 Hz. The optimized parameters ranged from 50% to 95% for porosity, 0.1 mm to 4.5 mm for pore size, and 0.07 mm to 0.6 mm for pore opening size. The result of this study was applied to fabricate the desired Aluminum metal foams for the best sound absorption. The novel approach applied in this study, is expected to be successfully applied in for best sound absorption in desired frequencies.  相似文献   

12.
SHAOYI JIANG 《Molecular physics》2013,111(14):2261-2275
A review is presented of this group's recent molecular simulation studies of self-assembled monolayers (SAMs) of alkanethiols on Au(111) surfaces. SAMs are very useful for the systematic alteration of the chemical and structural properties of a surface by varying chain length, tail group and composition. The scientific and technological importance of SAMs cannot be overestimated. The present work has been centred on studies of atomic scale surface properties of SAMs. First, configurational-bias Monte Carlo simulations were performed in both semigrand canonical and canonical ensembles to investigate the preferential adsorption and phase behaviour of mixed SAMs on Au(111) surfaces. Second, a novel hybrid molecular simulation technique was developed to simulate atomic force microscopy (AFM) over experimental timescales. The method combines a dynamic element model for the tip-cantilever system in AFM and a molecular dynamics relaxation approach for the sample. The hybrid simulation technique was applied to investigate atomic scale friction and adhesion properties of SAMs as a function of chain length. Third, dual-control-volume grand canonical molecular dynamics (DCV-GCMD) simulations were performed of transport diffusion of liquid water and methanol through a slit pore with both inner walls consisting of Au(111) surfaces covered by SAMs under a chemical potential gradient. Surface hydrophobicity was adjusted by varying the terminal group of CH3 (hydrophobic) or OH (hydrophilic) of the SAMs. Finally, ab initio quantum chemical calculations were performed on both clusters and periodic systems of methylthiols on Au(111) surfaces. Based on the ab initio results, an accurate force field capable of predicting c(4×2) superlattice structures over a wide range of temepratures for alkanethiols on Au(111) was developed. The extension of current work is discussed briefly.  相似文献   

13.
The interfacial interactions between inorganics and polymer matrix have important effects on the properties of nano-composites. A commercially available nano-SiO2 was modified by surface pretreatment with sulfonated polyethersulfone, which is a typical polyethersulfone (PES) derivative, and served as a macromolecular modifier in this paper to fabricate PES/SiO2 nano-composite films. The modified SiO2 phase was well dispersed in polymer matrix due to its unique structure and the satisfactory interfacial interaction between nano-particles and the PES matrix. Compared with pristine SiO2 as a ceramic filler, there was noticeable improvement in the transmission of light when modified SiO2 was used. Effects of surface modification on thermal stability were also studied by thermo-gravimetric analysis.  相似文献   

14.
飞秒激光脉冲持续时间短、峰值功率高,在对物质进行处理过程中热作用区域小、加工精度高,已成为一种制作高性能、新结构光子器件的重要方法。简单介绍了飞秒脉冲激光微加工的方法和特性,归纳了飞秒激光直写技术在光纤干涉型传感器制作方面的研究进展,包括微型光纤Fabry-Perot干涉传感器和微型光纤Mach-Zehnder干涉传感器,重点介绍了这些光纤传感器的结构、特性和潜在应用。对用该技术制作的微型光纤干涉传感器进行了总结和展望。  相似文献   

15.
Supramolecular self-assembly on surfaces offers attractive features, which are usually tuned through the choice of the chain-length-varying molecular building blocks and stabilized by hydrogen bonding. Here the linear nanopatterns of bi-component building blocks between 1,18-octadecanedionic acid (HOOC(CH2)18COOH) and 4,4′-bipyridine (BPy), 1-hydroxyhexadecanoic acid (HO(CH2)15COOH) and BPy on highly ordered pyrolytic graphite are presented. By merely changing terminal groups, we reveal by using scanning tunneling microscopy (STM) that it is rational to steer the periodicity of the linearly patterned nanostructures with nanometer precision over an extended length scale. Different surface nanopatterns on graphite surface are created by tuning different disubstituted terminal groups and the ratio of them to their complementary recognizing molecules. The STM observations are supported by the reference nanostructure of bi-component 1,16-hexadecandiol (HO(CH2)16OH) and BPy.  相似文献   

16.
The aim of the present study is to demonstrate the feasibility to form well-ordered nanoholes on InP(1 0 0) surfaces by low Ar+ ion sputtering process in UHV conditions from anodized aluminum oxide (AAO) templates. This process is a promising approach in creating ordered arrays of surface nanostructures with controllable size and morphology. To follow the Ar+ ion sputtering effects on the AAO/InP surfaces, X-ray photoelectron spectroscopy (XPS) was used to determine the different surface species. In4d and P2p core level spectra were recorded on different InP(1 0 0) surfaces after ions bombardment. XPS results showed the presence of metallic indium on both smooth InP(1 0 0) and AAO/InP(1 0 0) surfaces. Finally, we showed that this experiment led to the formation of metallic In dropplets about 10 nm in diameter on nanoholes patterned InP surface while the as-received InP(1 0 0) surface generated metallic In about 60 nm in diameter.  相似文献   

17.
We have theoretically and experimentally investigated the antireflective properties of the disordered subwavelength structures (SWSs) with a hydrophobic surface on silicon (Si) substrates by an inductively coupled plasma (ICP) etching in SiCl4/Ar plasma using thermally dewetted platinum (Pt) nanopatterns as etch masks for Si-based solar cells. The Pt thin films on the SiO2/Si surface were properly changed into the optimized dot-like nanopatterns via the thermal dewetting by rapid thermal annealing process. The antireflection properties were definitely affected by the etched profile of SWSs which can be controlled by the conditions of etching process. For the tapered Si SWS with a high average height of 724 ± 78 nm, the reflectance was significantly reduced below 5% over a wide wavelength range of 350-1030 nm, leading to a relatively low solar weighted reflectance of 2.6%. The structure exhibited reflectances less than 14.8% at wide incident angles of 8-70°. The hydrophobic surface with a water contact angle of 113.2° was obtained. For Si SWSs, the antireflective properties were also analyzed by the rigorous coupled-wave analysis simulation. These calculated results showed similar behavior to the experimental results.  相似文献   

18.
Substrate materials play an important role to modulate the photophysical properties of fluorescent self‐assembled monolayers (SAMs) constructed on them. The substrate–fluorophore interactions in fluorescent SAMs can affect their fluorescence intensity. Hence, it is important to take into account such alteration of fluorescence properties and study the underlying mechanisms. In this brief overview, substrate effects on fluorescence properties of chemisorbed or physisorbed fluorescent SAMs on two‐dimensional (chips) and three‐dimensional (nanoparticles) surfaces are highlighted. Examples of fluorescence quenching and enhancement on various substrate materials by different factors are discussed and analyzed. Additionally, some strategies to limit metallic substrate–fluorophore interactions are discussed briefly. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

19.
The effects of the different combined manner of ultrasound and covalent reaction between polyphenol and myofibrillar protein (MP) from chicken were studied. More so, antioxidant activities, digestive properties, and potential mechanism of ultrasound-assisted oxidation system of hydrophilic ((−)-Epicatechin gallate, ECG) and hydrophobic (Baicalein, BN) polyphenols was also analyzed in this study. Among all the combined treatments, surface hydrophobicity (SUH), active sulfhydryl contents (ASC), and specific surface area (SSA) of ultrasonic assisted ECG oxidation group (T6) was relatively apparent, indicating that a more unfolding MP structure was obtained. Furthermore, ultrasonic assisted ECG oxidation group showed the highest antioxidant activities compared with other combined treatments on the basis of the results of DPPH free radical scavenging activities, metal ion chelating activities, and hydroxyl radicals (OH·) scavenging activities. The results of simulated digestion system and kinetic analysis also verified that ultrasonic assisted ECG oxidation had higher MP bio-accessibility than the control group. In contrast, a lower digestibility was displayed in ultrasonic assisted BN oxidation group. In summary, the ultrasound-assisted covalent reaction of MP and ECG might be a desirable approach for industrial production of MP from chicken with better antioxidant activities and digestive properties.  相似文献   

20.
Silicon-on-insulator (SOI) wafers are commonly used to design microelectronics, energy conversion, and sensing devices. Thin solid films on the surfaces of SOI wafers have been a subject of numerous studies. However, SOI wafers modified by self-assembled monolayers (SAMs) that can also be used as functional device platforms have been investigated to a much lesser extent. In the present work, tert-butoxycarbonyl (t-boc, (CH3)3-C-O-C(O)-)-protected 1-amino-10-undecene monolayers were covalently attached to a H-terminated SOI (1 0 0) surface. The modified wafers were characterized by X-ray photoelectron spectroscopy to confirm the stability of the SAM/Si interface and the integrity of the secondary amine in the SAM. The transmission electron microscopy investigation suggested that this t-boc-protected 1-amino-10-undecene SAM produces atomically flat interface with the 2 μm single crystalline silicon of the SOI wafer, that the SiOx and both available Si/SiOx interfaces are preserved, and that the organic monolayers are stable, with apparent thickness of 1.7 nm, which is consistent with the result of the density functional theory modeling of the molecular features within a SAM.  相似文献   

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