In-situ formation and detailed analysis of imine bonds for the construction of conjugated aromatic monolayers on Au(111)

We present the synthesis of 4′-amino-4-mercaptobiphenyl (AMB) and its deposition from solution onto Au(111) substrates. The resulting organic thin films were characterized by contact angle, infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS) measurements. It is demonstrated that the majority of AMB molecules are coupled to the gold surface via S–Au covalent bonds, although only little orientational order of the AMB layer could be detected by NEXAFS. Furthermore, aromatic imine bonds between AMB and 4-hydroxybenzaldehyde (HB), 4-carboxybenzaldehyde (CB), 4-methylbenzaldehyde (MB), or 4-(trifluoromethyl) benzaldehyde (TMB) have been successfully formed. As a result of the limited order, this coupling reaction was incomplete. Nevertheless, the experimental results confirmed the formation of conjugated aromatic imine bonds.     

Characterization of ultra-thin organic hetero-interfaces — SnPc/PTCDA/Ag(111)

Ultra-thin organic hetero-layers consisting of tin-phthalocyanine (SnPc) and 1,3,4,8-perylen-tetracarboxylicacid dianhydride (PTCDA) adsorbed on a Ag(111) surface are characterized with photoelectron spectroscopy (PES) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. If SnPc is deposited on the Ag(111) substrate, which is precovered with one monolayer of PTCDA, a well defined interface is formed with a closed SnPc wetting layer as can be derived from angle dependent core level and from valence photoelectron spectra. Moreover, X-ray absorption data show that the molecules are lying flat and that the bonding at the SnPc/PTCDA interface is weak.     

Thin PTCDA films on Si(0 0 1): 1. Growth mode

We have studied the interface and thin film formation of the organic molecular semiconductor 3,4,9,10 perylene tetracarboxylic dianhydride (PTCDA) on clean and on hydrogen passivated Si(0 0 1) surfaces. The studies were made by means of high resolution X-ray photoelectron spectroscopy (HRXPS), near edge X-ray absorption fine structure (NEXAFS), low energy electron diffraction (LEED), and atomic force microscopy (AFM). On the passivated surface the LEED pattern is somewhat diffuse but reveals that the molecules grow in several ordered domains with equivalent orientations to the substrate. NEXAFS shows that the molecules are lying flat on the substrate. The Si 2p XPS line shape is not affected when the film is deposited so it can be concluded that the interaction at the interface between PTCDA and the substrate is weak. The evolution of the film formation appears to be homogeneous for the first monolayer with a nearly complete coverage of flat lying molecules based on the XPS attenuation. For layer thickness of 0.5-2 monolayers (ML) the molecules start to form islands, attracting the molecules in between, leaving the substrate partly uncovered. For thicker films there is a Stranski-Krastanov growth mode with thick islands and a monolayer thick film in between. For the clean surface the ordering of the film is much lower and angle resolved photoelectron spectroscopy (ARPES) of the molecular orbitals have only a small dependence of the emission angle. NEXAFS shows that the molecules do not lie flat on the surface and also reveal a chemical interaction at the interface.     

Microstructural inhomogeneity in plasma-sprayed hydroxyapatite coatings and effect of post-heat treatment

The microstructural inhomogeneity in the plasma-sprayed hydroxyapatite (HA) coatings was characterized by using electron probe microanalyser (EPMA). A simple and artful method was developed to detect the interface characteristics. All the samples for observation were ground and polished along the direction parallel to the coating surfaces. The BSE images directly and clearly showed the inhomogeneity in the as-sprayed coatings with the amorphous regions being bright gray and crystalline regions being dark gray. X-ray diffractometer (XRD) patterns indicated that after immersion in deionized water for 20 days, bone-like apatite and α-Ca₂P₂O₇ precipitated on the polished surfaces of the as-sprayed HA coatings. The post-heat treatment could eliminate the microstructural inhomogeneity in the coatings. Only β-Ca₂P₂O₇ precipitated on the surfaces of the heat-treated HA coatings. The immersed samples were re-polished till tiny substrate was bared to investigate the effect of immersion on interface. It was shown that the immersion decreased the cohesive strength of the as-sprayed coatings. There were more and broader cracks in the splats that came into contact with the substrate and amorphous phase increased toward the coating-substrate interface. Post-heat treatment was proved to reduce the peeling off of coating during re-polishing operation. It was proposed that the distributions of amorphous phase and cracks in as-sprayed coatings are detrimental to coating properties and should be modified through improving the plasma spraying processing.     

高数值孔径光刻成像中双层底层抗反膜的优化

在高数值孔径光学光刻中,成像光入射角分布在较大范围内,传统的单底层抗反膜不足以控制抗蚀剂-衬底界面反射率(衬底反射率)。考虑照明光源形状以及掩模的影响,提出了一种新的双层底层抗反膜优化方法,依据各级衍射光光强求衬底反射率的最小权重平均值来配置膜层。针对传统掩模、衰减相移掩模以及交替相移掩模的情况,用该方法优化双层底层抗反膜。结果表明,如果成像时进入物镜光瞳的高阶光越多,高阶光光强越大,则掩模对底层抗反膜优化的影响越大。在某些成像条件下,如使用交替相移掩模实现成像,有必要在底层抗反膜优化中考虑掩模的影响。     

极紫外多层膜技术研究进展

在极紫外波段,任何材料都表现出极强的吸收特性,因此,采用多层膜实现高反射率是构建正入射式光学系统的唯一途径。本文总结了极紫外多层膜的发展进程,叙述了制备极紫外多层膜的关键技术(磁控溅射、电子束蒸发、离子束溅射)以及它们涉及的相关设备。由于多层膜反射式光学元件主要应用于极紫外光刻与极紫外天文观测,文中重点讨论了极紫外光刻系统对多层膜性能的要求,镀膜过程中的面形精度和热稳定性等问题;同时介绍了极紫外天文观测中使用的多层膜的特点,特别讨论了多层膜光栅的制备技术和亟待解决的问题。     

Anchoring of alkyl chain molecules on oxide surface using silicon alkoxide

Chemical states of the interfaces between octadecyl-triethoxy-silane (ODTS) molecules and sapphire surface were measured by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) using synchrotron soft X-rays. The nearly self-assembled monolayer of ODTS was formed on the sapphire surface. For XPS and NEXAFS measurements, it was elucidated that the chemical bond between silicon alkoxide in ODTS and the surface was formed, and the alkane chain of ODTS locates upper side on the surface. As a result, it was elucidated that the silicon alkoxide is a good anchor for the immobilization of organic molecules on oxides.     

Room temperature synthesis of water repellent silica coatings by the dip coat technique

The present paper describes the room temperature synthesis of dip coated water repellent silica coatings onto stainless steel substrates using 1,1,1,3,3,3-hexamethyldisilazane as a surface modifying agent. The hydrophobic property of the silica coating was enhanced by increasing its surface roughness, which was achieved by a proper control over the MeOH/TMOS molar ratio (S) during the synthesis. The contact angle of a water droplet (10 μl) increased from 72° to 145° with an increase in the S value from 9.1 to 36.4. The silica coating showed a minimum sliding angle of 15° for a water droplet of 10 μl. The water repellent silica coatings are thermally stable up to a temperature of 340 °C. The results have been discussed by taking into consideration the contact angle measurements, surface morphology and sol-gel parameters.     

Properties of oxide films on nickel contact surfaces

The possibilities of changing the conductivity of surface films during electrolysis are studied. The results of experimental research into films on nickel contacts are presented. From a comparison of ellipsometric, X-ray diffraction, and Auger-spectrum measurements of nickel coating surfaces obtained from electrolytes with organic components, it is revealed that the structure and composition of the surface films undergo changes which result in a decrease in the contact resistance. This makes it possible to employ such films in low-current contacts instead of silver or silver-alloy coatings.     

Two component silicone modified epoxy foul release coatings: Effect of modulus, surface energy and surface restructuring on pseudobarnacle and macrofouling behavior

Two component silicone modified epoxy resin based low surface energy and non-toxic foul release coatings were developed. Silicone modified epoxy resin with 15 and 30% silicone content was used as component A and a polyether diamine (Jeffamine-500) was used as the component B. Free standing films were prepared by casting a mixture of components A and B in stoichiometric proportions. The surface composition, surface topography and wetting properties of the coatings were studied by angle resolved X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle goniometry respectively. The mechanical properties of the cured films were evaluated by tensile measurements as well as dynamic mechanical analysis. Pseudobarnacles made of aluminium studs were attached to the coated panels and adhesion tests were carried out by a pseudobarnacle tester. Coated panels were exposed in Mumbai harbor for fouling studies for a period of 90 days. Surface restructuring studies of the coatings upon immersion in seawater were carried out by measuring the changes in advancing and receding contact angles by contact angle goniometry. The effect of surface energy, modulus and surface restructuring of the coatings on the macrofouling and pseudobarnacle adhesion properties has been discussed in detail.     

Surface free energies of electroless Ni–P based composite coatings

Surface free energy of a solid surface gives a direct measure of intermolecular interactions at interfaces and has a strong influence on adsorption and adhesion behaviour. However few data are available for the surface free energies of electroless Ni–P based composition coatings. In this paper, the electroless Ni–P, Ni–P-surfactant, Ni–Cu–P, Ni–P–PTFE and Ni–Cu–P–PTFE composite coatings were prepared under various coating conditions. The chemical compositions, surface morphology and thickness of the coatings were measured using an energy dispersive X-ray microanalysis (EDX), a scanning electron microscope (SEM) and a digital micrometer respectively. The contact angles of water, diiodomethane and ethylene glycol on the coatings were measured automatically using dataphysics OCA-20 contact angle analyser. The surface free energy of the coatings and their components (e.g. dispersion, polar or acid/base portions) were calculated using various methods. The experimental results showed that the incorporation of surfactant or PTFE particles into Ni–P matrixes has a significant influence on the surface free energy of the coatings, while the incorporation of copper into Ni–P matrixes has no significant influence on the surface free energy of the coatings.     

Fabrication of superhydrophobic polyurethane/organoclay nano-structured composites from cyclomethicone-in-water emulsions

Nano-structured polyurethane/organoclay composite films were fabricated by dispersing moisture-curable polyurethanes and fatty amine/amino-silane surface modified montmorillonite clay (organoclay) in cyclomethicone-in-water emulsions. Cyclomethicone Pickering emulsions were made by emulsifying decamethylcyclopentasiloxane (D₅), dodecamethylcyclohexasiloxane (D₆) and aminofunctional siloxane polymers with water using montmorillonite particles as emulsion stabilizers. Polyurethane and organoclay dispersed emulsions were spray coated on aluminum surfaces. Upon thermosetting, water repellent self-cleaning coatings were obtained with measured static water contact angles exceeding 155° and low contact angle hysteresis (<8°). Electron microscopy images of the coating surfaces revealed formation of self-similar hierarchical micro- and nano-scale surface structures. The surface morphology and the coating adhesion strength to aluminum substrates were found to be sensitive to the relative amounts of dispersed polyurethane and organoclay in the emulsions. The degree of superhydrophobicity was analyzed using static water contact angles as well as contact angle hysteresis measurements. Due to biocompatibility of cyclomethicones and polyurethane, developed coatings can be considered for specific bio-medical applications.     

苝四甲酸二酐在Au(111)表面的取向生长及电子结构研究

利用X射线光电子能谱(XPS),同步辐射紫外光电子能谱(SRUPS),近边X射线吸收精细结构(NEXAFS)以及原子力显微镜(AFM)等技术研究了苝四甲酸二酐(PTCDA)与Au(111)的界面电子结构、PTCDA分子取向及有机薄膜的表面形貌.SRUPS价带谱显示,伴随PTCDA分子的微量沉积(0·5ML),位于费米能级附近Au的表面电子态迅速消失,但却观察不到明显的界面杂化态,这说明PTCDA分子和Au(111)界面间存在弱电子传输过程,但并没有发生明显的化学反应.角分辨NEXAFS以及SRUPS结果证明PTCDA分子是平铺在衬底表面.根据Au4f7/2和C1s峰积分强度随薄膜厚度的变化以及AFM图像可知,PTCDA分子在Au(111)表面是一种典型的Stranski-Krastanov生长模式,即先层状生长,再岛状生长,并且在层状生长到岛状生长的转变过程中,存在有机分子的去润湿过程.     

Wettability of ZnO: A comparison of reactively sputtered; thermally oxidized and vacuum annealed coatings

We have studied the wettability of sputter deposited ZnO, thermally oxidized Zn-ZnO and vacuum annealed ZnO coatings. The X-ray diffraction patterns showed the formation of hexagonal-wurtzite structure of ZnO, which was further confirmed by micro-Raman spectroscopy data. The X-ray photoelectron spectroscopy data indicated that the sputter deposited ZnO coatings were more stoichiometric than thermally oxidized Zn-ZnO and vacuum annealed ZnO coatings. The wettability measurements indicated that water contact angles of 158.5° and 155.2° with sliding angles of 2° and 4° were achieved for thermally oxidized Zn-ZnO and vacuum annealed ZnO coatings, respectively. The superhydrophobicity observed in thermally oxidized Zn-ZnO and vacuum annealed coatings is attributed to the nanorod cluster like morphology along with the presence of high fraction of micron scale air pockets. The water droplet on such surfaces is mostly in contact with air pockets rather than solid surface, leading to high contact angle. Whereas, the sputter deposited ZnO coatings exhibited a maximum water contact angle of 110.3°. This is because the sputter deposited ZnO coatings exhibited a densely packed nanograin-like microstructure without any air pockets. The work of adhesion of water was very low for thermally oxidized Zn-ZnO (5.06 mJ/m²) and vacuum annealed ZnO coatings (6.71 mJ/m²) when compared to reactively sputtered ZnO coatings (90.41 mJ/m²). The apparent surface free energy (SFE) for these coatings was calculated using Neumann method and the SFE values for sputter deposited ZnO, thermally oxidized Zn-ZnO and vacuum annealed ZnO coatings were 32.95, 23.21 and 18.78 mJ/m², respectively.     

Fabrication of a superhydrophobic surface on a wood substrate

A layer of lamellar superhydrophobic coating was fabricated on a wood surface through a wet chemical process. The superhydrophobic property of the wood surface was measured by contact angle (CA) measurements. The microstructure and chemical composition of the superhydrophobic coating were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). An analytical characterization revealed that the microscale roughness of the lamellar particles was uniformly distributed on the wood surface and that a zinc stearate monolayer (with the hydrophobic groups oriented outward) formed on the ZnO surface as the result of the reaction between stearic acid and ZnO. This process transformed the wood surface from hydrophilic to superhydrophobic: the water contact angle of the surface was 151°, and the sliding angle was less than 5°.     

NEXAFS microscopy studies of the association of hydrocarbon thin films with fine clay particles

The nature of organic species associated with clay minerals plays a significant role in several processes, from hydrocarbon recovery in oil sands to contaminated soil remediation and water treatment. In this work, we address the use of scanning transmission X-ray microscopy (STXM) in conjunction with near edge X-ray absorption fine structure (NEXAFS) spectroscopy to study the microstructure and chemistry of organic–clay associations in situ. A model system based on methylene blue and illite is used to explore the sensitivity of NEXAFS microscopy to these interactions, and to identify and resolve experimental challenges in these measurements. We find that sample contamination from X-ray induced photodeposition is a significant problem in STXM microscopy, but also that this problem can be substantially reduced with a liquid nitrogen cooled anticontaminator. With appropriate sample preparation and experimental procedures, we find that STXM microscopy is sensitive to thin carbon adsorbates on clay surfaces.     

Probing the adsorption structure of a multifunctional organic molecule: a NIXSW and NEXAFS study of 3-chlorothiophene on Cu(111)

The adsorption structure of 3-chlorothiophene on Cu(111) has been investigated using a combination of normal incidence X-ray standing wavefield absorption (NIXSW) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. For coverages up to saturation of the chemisorbed layer, the 3-chlorothiophene bonds through the S atom. The S atom adsorbs in an atop site with a Cu–S distance identical, within experimental error, to that observed for thiophene on the same substrate. From a combination of NEXAFS and NIXSW, thiophene was found to adsorb with the aromatic ring flat lying. From NIXSW measurements the S–Cl axis was found to be inclined by 12±2° from the surface. Whilst NEXAFS data suggested an orientation of 23±8° for the aromatic ring of 3-chlorothiophene. The Cl atom interacted only weakly with the substrate, with a Cl–surface distance longer than the Cu–Cl van der Waal separation.     

Morphological control of polymerized n-octadecylsiloxane

Polymerized n-octadecylsiloxane (PODS) was prepared by coating glass substrates with liquid ocatdecyltrichlorosilane (OTS) followed by dipping-in a solvent. The morphology control of PODS was investigated by the post curing temperature as well as the use of different solvents. The resulting substrates were characterized by scanning electron microscopy (SEM), contact angle measurements, and wide angle X-ray diffractometry (XRD). It is shown that both post curing temperature and extracting solvents affect the morphology of PODS. The temperature dependent morphology was investigated and is ascribed to the physiochemical properties of PODS. For the solvent-dependent morphology, it is proposed that the solvation capability of a solvent to OTS and the presence of a hydrophilic/hydrophobic interface are critical in the PODS morphology. This paper shows the controlling parameter and possible explanation in the crystallinity and wettability of PODS films, which may be useful to other silane-based systems.     

Development and evaluation of electroless Ag-PTFE composite coatings with anti-microbial and anti-corrosion properties

Electroless Ag-polytetrafluoroethylene (PTFE) composite coatings were prepared on stainless steel sheets. The existence and distribution of PTFE in the coatings were analysed with an energy dispersive X-ray microanalysis (EDX). The contact angle values and surface energies of the Ag-PTFE coatings, silver coating, stainless steel, titanium and E. coli Rosetta were measured. The experimental results showed that stainless steel surfaces coated with Ag-PTFE reduced E. coli attachment by 94-98%, compared with silver coating, stainless steel or titanium surfaces. The anti-bacterial mechanism of the Ag-PTFE composite coatings was explained with the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The anticorrosion properties of the Ag-PTFE composite coatings in 0.9% NaCl solution were studied. The results showed that the corrosion resistance of the Ag-PTFE composite coatings was superior to that of stainless steel 316L.     

The thermal contact problem in nano- and micro-scale photothermal measurements

Thermal contact resistance between two solids is discussed with regard to its influence on the measurements of temperature and thermo-physical parameters in micro- and nano-structures. Two important applications are considered: thin film coatings on substrates and local measurements with a nano-probe in scanning thermal microscopy. The mechanical contact of a copper layer on carbon is measured by adhesion strength experiments and correlated to the thermal transport across the interface deduced from infrared radiometric measurements. A novel quantity the thermal wave contrast is introduced which takes into account the interface resistance and modifications of the coating and substrates at the interface. With regard to scanning thermal microscopy the contact resistance problem is discussed for 3ω-measurements in the active mode and for temperature measurements in the passive mode. It is shown that the thermo-elastic response can offer a means to avoid the influence of the thermal contact resistance on local temperature measurements.