Wettability of porous two‐dimensional ZnO nanocrystal films

Large‐scale two‐dimensional ZnO nanocrystal films on aluminum substrate were fabricated by a one‐step hydrothermal method under mild conditions, where all the ZnO nanocrystals had a lamellar structure generally perpendicular to the substrates and formed network‐like porous configurations. The morphologies of the films were dependent on both the reaction temperature and concentration of zinc. The wettability of the ZnO films was assessed by measuring the water contact angle without any surface functionalisation. The porous structures of the as‐prepared films could effectively enhance its hydrophobicity and the water contact angle ranged from 40° to 135° depending on the surface morphology and the arrangement of ZnO planes, indicating a simple and promising route to make aluminum surface waterproof and even self‐cleaning. The hydrophobic ZnO surface could be switched to hydrophilic state by UV irradiation.     

Polymeric semiconducting carbon from fullerene by pulsed laser ablation

The polymeric semiconducting carbon films are grown on silicon and quartz substrates by excimer (XeCl) pulsed laser deposition (PLD) technique using fullerene C₆₀ precursor. The substrate temperature is varied up to 300 °C. The structure and optical properties of the films strongly depend on the substrate temperature. The grain size is increased and uniform polymeric film with improved morphology at higher temperature is observed. The Tauc gap is about 1.35 eV for the film deposited at 100°C and with temperature the gap is decreased upto 1.1 eV for the film deposited at 250 °C and increased to about 1.4 eV for the film deposited at 300 °C. The optical absorption properties are improved with substrate temperature. Raman spectra show the presence of both G peak and D peak and are peaked at about 1590 cm^− 1 and 1360 cm^− 1, respectively for the film deposited at 100 °C. The G peak position remains almost unchanged while D peak has changed only a little with temperature might be due to its better crystalline structure compared to the typical amorphous carbon films and might show interesting in device such as, optoelectronic applications.     

Optimization of amphiphobic structural surface thickness in relation to its functionality on stainless steel plates

Fluorine‐based amphiphobic coatings have been widely used in commercial textiles to provide water‐ and oil‐repelling abilities. However, few reports from the literature survey have discussed the surface structural effects of the coated substrate on amphiphobicity. In this research, various thickness amphiphobic coatings based on mixed epoxy, tetraethylorthosilicate, and a particular alkoxysilane with fluorinated side chains (F‐silane) were deposited on Grade 420 stainless steel plates. Film amphiphobicity is characterized by measuring the water and oil contact angles of the coating. Film morphology is examined using atomic force microscopy. The deposited films free of F‐silane are thinner than 150 nm. The films become thick at high F‐silane volume percentage with the surface cavities, ridges, and granules being masked out. On the addition of F‐silane, the water contact angle of the deposited films increases up to 105° and then reaches a plateau of ～ 107° with increasing F‐silane. In contrast, the oil contact angle increases up to 60° at first and then slowly declines with the F‐silane concentration. The total drop of oil contact angle by ～ 20° was attributed to the masking out of surface features on film thickening. This indicates that the surface oleophobicity depends on surface structures. Therefore, improving surface amphiphobicity correlates with creating more refined multiscale surface structures during the industrial manufacturing process of steel plate, prior to surface modification by F‐silane. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41003.     

Hybrid multilayer thin-film fabrication by atmospheric deposition process for enhancing the barrier performance

In this paper, a multilayer barrier thin film, based on polyvinylidene difluoride (PVDF)–silicon dioxide (SiO₂), has been fabricated on a PET substrate through a novel method of joint fabrication techniques. The inorganic SiO₂ thin film was deposited using a roll-to-roll atmospheric atomic layer deposition system (R2R-AALD), while the organic PVDF layer was deposited on the surface of SiO₂ through the electrohydrodynamic atomization (EHDA) technique. The multilayer barrier thin films exhibited very good surface morphology, chemical composition, and optical properties. The obtained values for arithmetic surface roughness and water contact angle of the as-developed multilayer barrier thin film were 3.88 nm and 125°, respectively. The total thickness of the multilayer barrier thin film was 520 nm with a high optical transmittance value (85–90%). The water vapor transmission rate (WVTR) of the barrier thin film was ~?0.9?×?10^?2 g m^?2 day^?1. This combination of dual fabrication techniques (R2R-AALD and EHDA) for the development of multilayer barrier thin films is promising for gas barrier applications.     

Anisotropy and densification of polymer ultrathin films as seen by multi-angle ellipsometry and X-ray reflectometry

The chain conformations of cyclo-olefin polymer (COP) and polystyrene (PS) in less than 200-nm thick films on silicon wafers were investigated on the basis of the refractive index measured by multi-angle spectroscopic ellipsometry (MASE), and density measured by X-ray reflectometry (XRR). For both COP and PS, the density measured by XRR increases by decreasing the film thickness to below 50 nm. Densification may be caused by close packing of unentangled polymer chains in ultrathin films spincast from dilute solutions with polymer concentrations less than the overlap concentration (C*). For COP films, the refractive indices at incident angles of 45° and 70° measured by MASE agree well with those calculated by the Lorentz–Lorenz equation, indicating that densification of COP ultrathin films enhances their refractive indices. For PS films thinner than 50 nm, although the refractive index at an incident angle of 45° agrees with a calculation based on the Lorentz–Lorenz equation, one at 70° significantly deviates downward. A comparison of them with the results of quantum chemical calculation (QCC) suggested a plane-arrangement of benzene rings in PS ultrathin films, which was likely brought about by stacking of benzene rings and attractive interaction between π-electrons in the benzene rings and the substrate surface.     

Growth behavior of titanium dioxide thin films at different precursor temperatures

The hydrophilic TiO₂ films were successfully deposited on slide glass substrates using titanium tetraisopropoxide as a single precursor without carriers or bubbling gases by a metal-organic chemical vapor deposition method. The TiO₂ films were employed by scanning electron microscopy, Fourier transform infrared spectrometry, UV-Visible [UV-Vis] spectroscopy, X-ray diffraction, contact angle measurement, and atomic force microscopy. The temperature of the substrate was 500°C, and the temperatures of the precursor were kept at 75°C (sample A) and 60°C (sample B) during the TiO₂ film growth. The TiO₂ films were characterized by contact angle measurement and UV-Vis spectroscopy. Sample B has a very low contact angle of almost zero due to a superhydrophilic TiO₂ surface, and transmittance is 76.85% at the range of 400 to 700 nm, so this condition is very optimal for hydrophilic TiO₂ film deposition. However, when the temperature of the precursor is lower than 50°C or higher than 75°C, TiO₂ could not be deposited on the substrate and a cloudy TiO₂ film was formed due to the increase of surface roughness, respectively.     

Polymer Masks Fabrication by Micropatterning Surfaces of Composite Polymer Coatings

Abstract

Micropatterning of surfaces has been demonstrated using composite polymer coatings of PS and PMMA of equal molecular weights in different volume proportions with varying surface topographies on silicon surfaces. The creation of PMMA masks with various surface morphological features has also been demonstrated by removal of PS from the composite coatings using cyclohexane. Atomic force microscopy (AFM) investigations revealed that the surface pattern and the dimensions of these masks significantly changed with the change in the volume proportions of each homopolymer. The composite coatings of 20/80 vol% PS/PMMA, 50/50 vol% PS/PMMA, and 80/20 vol% PS/PMMA resulted in PMMA masks with holes (depth ～300 nm), wrinkles (height ～350 nm) and pillars (height ～600 nm), respectively. Surface compositional analysis carried out using FTIR and XPS investigations confirmed the presence of polymer coatings of PS, PMMA and PS/PMMA. XPS investigations also confirmed the successful removal of PS from the PMMA mask by showing the presence of the silicon substrate on those masks where PS was previously present. The water contact angle of the composite polymer masks ranged from 70 to 90° which increased with the increase of PS vol% in the composite. The wetting behavior of certain PMMA masks showed hydrophobicity with water contact angle values above 90°.     

Preparation and tribological properties of polymer film covalently bonded to silicon substrate via an epoxy-terminated self-assembled monolayer

A covalently immobilized polymer film was constructed on silicon substrate by a two-step method. As an anchor interlayer, (3-glycidoxypropyl)trimethoxysilane (GPMS) was self-assembled on hydroxylated silicon substrate to create epoxy-terminated surface, then poly(styrene-b-acrylic acid) (PSAA) was chemically grafted to the epoxy-derivatized substrates. The formation and surface properties of the films were characterized by means of ellipsometry, water contact angle measurement, attenuated total reflectance Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, and atomic force microscope (AFM). The nano- and micro-tribological properties of the films were evaluated by AFM and ball-on-plate tribometer, respectively. The results show that GPMS–PSAA film exhibits excellent durability and wear resistance, which is attributed to the molecular components of PSAA and the firm bonding between polymer molecules and silicon substrate via epoxysilane molecular glue. The influence of interlayer between polymer and substrate surface on tribological properties of ultrathin polymer film was revealed, which has an important significance upon designing ultrathin lubrication films with excellent tribological properties for micro/nanoelectromechanical systems.     

Improvements in CVD/CVI processes for optimizing nanocrystalline diamond growth into porous silicon

This paper reports a novel procedure to infiltrate nanocrystalline diamond films (NCD) on porous silicon (PS) substrate. The NCD/PS films resulted in a composite material, with great potential for electrochemical application, mainly due to its high active surface area. The Hot Filament Chemical Vapor Deposition reactor was changed to Hot Filament Chemical Vapor Infiltration reactor in order to grow NCD films infiltrated into deep holes of PS substrate. This procedure allowed the infiltration of the reacting gases into the porous structure where the nucleation takes place, followed by the coalescence and film formation at pore bottoms and walls. In this configuration an additional entrance of CH₄ was located next to the PS substrate using two distinct positions called “underneath” and “above”, with the use of the additional flow accurately underneath or above of the samples. In general, the combination of these two configurations with additional carbon sources provided NCD film infiltration in PS substrate with success with only 60 min of growing time. Particularly, the films obtained from the positions called “above” presented the best morphology, with high quality and crystallinity, confirmed from its scanning electron microscopy, Raman scattering spectroscopy and high resolution X-ray diffraction spectra, respectively.     

Effect of oxygen plasma treatment on non-thrombogenicity of diamond-like carbon films

The non-thrombogenicity of oxygen-plasma-treated DLC films was investigated as surface coatings for medical devices. DLC films were deposited on polycarbonate substrates by a radio frequency plasma enhanced chemical vapor deposition method using acetylene gas. The deposited DLC films were then treated with plasma of oxygen gas at powers of 15 W, 50 W, and 200 W. Wettability was evaluated by water contact angle measurements and the changes in surface chemistry and roughness were examined by X-ray photoelectron spectroscopy and atomic force microscope analysis, respectively. Each oxygen-plasma-treated DLC film exhibited a hydrophilic nature with water contact angles of 11.1°, 17.7° and 36.8°. The non-thrombogenicity of the samples was evaluated through the incubation with platelet-rich plasma isolated from human whole blood. Non-thrombogenic properties dramatically improved for both 15 W- and 50 W-oxygen-plasma-treated DLC films. These results demonstrate that the oxygen plasma treatment at lower powers promotes the non-thrombogenicity of DLC films with highly hydrophilic surfaces.     

Hydrophobic and superhydrophobic surfaces fabricated by plasma polymerization of perfluorohexane,perfluoro(2-methylpent-2-ene), and perfluoro(4-methylpent-2-ene)

Fluoropolymer films were deposited on silicon (1 0 0) wafers, glass, epoxy, and hierarchical dual-sized filler epoxy composite surfaces by plasma polymerization of perfluorohexane, perfluoro(2-methylpent-2-ene), and perfluoro(4-methylpent-2-ene). The procedure involved continuous wave plasma-enhanced deposition, followed by a discharge-off period, with the monomer gas feed maintained. Silanization of silicon wafers and glass surfaces with triethoxyvinylsilane was employed to improve plasma fluoropolymer bonding to these substrates. The presence of double bonds in perfluoro(2-methylpent-2-ene) and perfluoro(4-methylpent-2-ene) was found to influence fluoropolymer coating topography, thereby increasing surface roughness in modified glass and epoxy substrates. All fluorocarbons provided a similar level of hydrophobization of flat substrates, exhibited by water contact angles (WCA) of about 110°. Hydrophobization of nanocomposite hierarchical surfaces by plasma polymerization provided superhydrophobic surfaces, with WCA of 160° and contact angle hysteresis below 8°.     

Optical characterization of ultrananocrystalline diamond films

Optical properties of the ultrananocrystalline diamond films were studied by multi-sample method based on the combination of variable angle spectroscopic ellipsometry and spectroscopic reflectometry applied in the range 0.6–6.5 eV. The films were deposited by PECVD in a conventional bell jar (ASTeX type) reactor using dual frequency discharge, microwave cavity plasma and radio frequency plasma inducing dc self-bias at a substrate holder. The optical model of the samples included a surface roughness described by the Rayleigh–Rice theory and a refractive index profile in which Drude approximation was used. The results conformed with the present understanding of the polycrystalline diamond growth on the silicon substrate because the existence of silicon carbide and amorphous hydrogenated carbon film between the silicon substrate and nucleation layer was proved.     

光催化多孔TiO2薄膜的表面形貌对亲水性的影响

从含聚乙二醇（ＰＥＧ）的钛醇盐溶胶前驱体中通过溶胶－凝胶工艺在普通钠钙玻表面制备了多孔锐钛矿型ＴｉＯ２纳米薄膜。用扫描电镜（ＳＥＭ）,Ｘ射线光电子能谱（ＸＰＳ）和红外光谱（ＩＲ）分析了ＴｉＯ２薄膜表面的微结构,结果表明,随着前驱物中聚乙二醇的加入量和分子量的增加,聚乙二醇热分解后的薄膜中产生的气孔就越多且孔径越大,同时ＴｉＯ２薄膜表面的羟基含量增加且表面粗糙度增大。接触角测试表明：随着薄膜中气孔数     

Origin of Different Growth Modes for Epitaxial Manganite Films

The microstructures of the Bi_0.4Ca_0.6MnO₃ (BCMO) and La_0.67Ca_0.33MnO₃ (LCMO) epitaxial films are investigated by transmission electron microscopy in detail. BCMO epitaxial films (~ 10 and ~ 40 nm) exhibit an island growth mode whereas the LCMO films (~ 6 and ~ 30 nm) follow a layer by layer growth mode. Combined with the critical thickness models for the expected onset of the misfit dislocations in epitaxial films, an atomic collapse model is introduced to explain their mechanism of formation in manganite films. At the beginning of deposition, the strain caused by the lattice mismatch between the epitaxial film and substrate can be accommodated by elastic deformation. With the increase of film thickness, the strain becomes larger and larger. When the film thickness reaches the critical thickness, the strain can only be relaxed by the formation of misfit dislocations. Meanwhile, the atomic configuration of the epitaxial film will reorganize and some atoms begin to collapse, thus an island morphology will be formed. Once the collapse morphology is formed, maintenance of this wave‐like morphology depends on atomic diffusion length of the deposited atoms. If the diffusion length of the deposited atoms is long, the island morphology will not be maintained. If the diffusion length of the deposited atoms is short, the island morphology will keep until the epitaxial film is thick enough. The results could shed light on the growth modes for other perovskite epitaxial films.     

射频磁控溅射法制备FC/ZnO杂化材料及其基本性质

采用射频磁控溅射法,首先以聚四氟乙烯（PTFE）为靶,氩气为载气,在聚对苯二甲酸乙二醇酯（PET）基底上沉积氟碳（FC）膜;然后以金属锌为靶,氩气为载气,氧气为反应气体,在FC膜上再沉积一层ZnO膜而形成FC/ZnO有机-无机纳米杂化材料。用AFM、XPS、UV以及静态接触角测定仪对杂化材料的基本性质进行了研究。结果表明,该法制得的杂化材料是由纳米粒子组成的岛状结构,岛的表面起伏不平。其生长模式是一种依附于有机核的沉积-扩张生长。杂化材料具有较好的紫外吸收特性,这是由于其分子结构中含有π-π共轭双键、表面的不平整性以及纳米氧化锌粒子对紫外光的吸收共同作用的结果。静态水接触角均大于90°,呈现出良好的疏水性。     

Engineering of morphological,optical, structural,photocatalytic and catalytic properties of nanostructured CuO thin films fabricated by reactive DC magnetron sputtering

Nanostructured thin films of CuO were deposited on silica glass substrates using reactive DC magnetron sputtering technique. Microstructural, morphological, optical, catalytic and photocatalytic properties of the prepared CuO thin films were examined using FESEM, AFM, Rutherford backscattering spectrometry, XRD, XPS, UV–Vis absorption and PL spectroscopy. FESEM showed nanostructures in the thin films, which were confirmed to be of monoclinic CuO by XRD analysis. Substrate temperature variation (40 °C, 100 °C and 300 °C) was found to significantly alter the optical, morphological, photocatalytic and structural properties of the CuO nanostructured thin film coatings. FESEM and AFM analyses showed decrease in size of nanostructures and surface roughness increase with increase in substrate temperature. Increase in UV–Vis absorbance and PL intensity of CuO thin films with decrease in crystallite size were noticed as the substrate temperature was increased. The prepared nanostructured CuO thin films exhibited highly enhanced photocatalytic activities and degraded dyes (MB and MO) in water in just 40 min under solar exposure and catalytic transformation of 4-nitrophenol (4-NP) took place in just 15 min. The developed CuO nanostructured thin film coatings are very promising for large scale, practical and advanced catalytic reduction of toxic 4-NP and photocatalytic applications in solar driven water purification.     

Poly(methyl methacrylate) as masking material for microelectromechanical system (MEMS) fabrication

In the present study direct current (dc) sputtered poly(methyl methacrylate) (PMMA) films deposited on silicon substrates were evaluated as masking materials for anisotropic etching of silicon in aqueous potassium hydroxide (KOH) and tetramethyl ammonium hydroxide (TMAH) solutions. Sputtered PMMA films were characterized by FTIR to ascertain the bonding, by X‐ray photoelectron spectroscopy (XPS) for the elemental composition, and by the contact angle for measuring the adhesion of the film with the substrate. FTIR and XPS data showed the presence of a poly(tetrafluoroethylene)‐like film on the silicon substrate. The interfacial tension was calculated from the contact angle value, which was 0.82 dyne/cm, confirming good adhesion of the film and the substrate. A pattern was lithographically transferred through the masking material on the silicon substrate, and the etch rate of the masking layer was calculated from the masking time data of the films. The etch rate value of 4 Å/min obtained for the masking material is low compared to the etch rate of the conventional masking materials (60 Å/min for SiO₂ and 8 Å/min for Si₃N₄). © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 2094–2098, 2006     

Preparation, characterization and wettability of porous superhydrophobic poly (vinyl chloride) surface

A porous superhydrophobic poly (vinyl chloride) surface was obtained by a simple approach. The water contact angle and the sliding angle of the superhydrophobic poly(vinyl chloride) surface were 154 ± 2.3o and 7o, respectively. The porous superhydrophobic PVC surface remained superhydrophobic property in the pH range from 1 to 13. When the superhydrophobic PVC surface was immersed in water with the temperatures ranging from 5 °C to 50 °C for 1 h to 30 days, the water contact angle remained higher than 150°. After outdoor exposure for 30 days, the contact angle still remained 150o.     

Porous water repellent silica coatings on glass by sol–gel method

Development of the solid surfaces with water-repellent and self-cleaning ability has attracted much research interest in recent years. In the present research work, we have prepared water repellent silica coatings on glass at room temperature (~27 °C) by sol gel process and surface silylation technique. Coating sol was prepared by keeping the molar ratio of tetramethoxysilane (TMOS), methanol (MeOH) and water (H₂O) constant at 1:12.36:4.25, respectively, with 0.01 M NH₄F. The dip coated silica films were surface silylated using two different silylating agents namely hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDZ). The HMDSO and HMDZ in hexane solvent were varied from 0 to 1 vol.% and silylation period was varied from 1 to 3 h. The HMDSO and HMDZ modified films showed dense and porous surface morphology, respectively. The HMDSO modified silica films showed static water contact angle of 122° whereas HMDZ modified films showed 165°. The HMDZ modified films displayed the extreme water repellency comparing with that of lotus leaves. The silica films were characterized by surface profilometer, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared microscopy, thermal and chemical aging tests, optical transmission and static water contact angle measurements.     

Surface morphology of PECVD fluorocarbon thin films from hexafluoropropylene oxide, 1,1,2,2‐tetrafluoroethane,and difluoromethane

Atomic force microscopy (AFM) measurements have been made on a series of fluorocarbon films deposited from pulsed plasmas of hexafluoropropylene oxide (HFPO), 1,1,2,2‐tetrafluoroethane (C₂H₂F₄), and difluoromethane (CH₂F₂). All of the films give images showing nodular growth (cauliflower‐like appearance), with the size and distribution of the nodules dependent on both the precursor, the degree of surface modification to which the growing film is exposed, and the substrate surface. Films deposited from C₂H₂F₄ showed clusters of smaller nodules around larger nodules, whereas films deposited from CH₂F₂ were characterized by a uniform distribution of smaller nodules, and films deposited from HFPO had the largest observed nodules. Movchan and Demchishin's structure zone model was applied to the observed films, which were all found to be zone 1 structures, indicating that film growth is dominated by shadowing effects. Increased substrate temperature and incident power per nm of film deposited results in decreased rms roughness, consistent with greater atomic mobility during deposition. Larger nodules in the fluorocarbon films developed on silicon wafer substrates than on rougher Al‐coated substrates. Advancing contact angles for all of the films were found to be higher than that of PTFE (108°), indicating both hydrophobic and rough surfaces. Specifically, contact angles of films deposited from HFPO were found to increase with pulse off‐time, the same trend observed for both the CF₂ fraction of the film and the rms roughness. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2439–2447, 1999