正电子湮没技术在高分子薄膜研究中的应用

介绍了正电子湮没技术在高分子薄膜研究中的最新进展.常规的正电子湮没技术和慢正电子湮没技术,可以准确地探测高分子薄膜微观缺陷(自由体积)尺寸、分数、浓度、深度分布,该测试技术将在研究各种高分子薄膜的微结构-性能关系、表面效应、界面效应等方面发挥积极的作用.     

Measurement and the effect of different solvents on thin polymericfilm surface resistance

A method of measuring the thin polymeric film surface resistance has been developed. The method uses an arrangement of concentric cylindrical electrodes for the measurements and has been studied analytically and experimentally. The effect of different solvents on the thin polymeric film surface resistance as well as the use of the method are examined. The mathematical modeling of the cylindrical electrode measuring system fitted the experimental results     

Ion-beam modifications of the surface morphology and conductivity in some polymer thin films

Studies on the surface micromorphology and surface conductivity in thin polymer films of poly vinyl alcohol (PVA) and poly ethylene oxide (PEO) in both as-grown and ion-implanted polymer films have been carried out to reveal certain specific features of the ordered state in these materials. Optical microscopic investigations revealed the existence and enhanced formation in number of spherulites and dendrites in ion-implanted films relative to the as-grown films. The number and rate of formation of spherulites indicated an increase in the degree of crystallinity in these films. Measurements of surface conductivity of as-grown and ion-implanted polymer films, employing four-point probe method, indicated a decrease in electrical conductivity on ion-implantation. Photomicrographic analysis of the PVA and PEO thin film surfaces, has enabled to propose a temperature-stress induced mechanism of crystallization in conjunction with the surface conductivity measurements. The decrease in surface conductivity on ion-implantation in both PVA and PEO thin films, is attributed to a decrease in mobility of macromolecular charged species due to an increase in degree of crystallinity as has been observed by optical microscopy.     

The use of silane coupling agents in the design of electrically stable interfaces of 6061 T6 aluminum alloy surfaces and epoxy-based electrically conductive adhesives

Electrically conductive interfaces between metal surfaces, including aluminum, are commonly formed by means of bonding with an electrically conductive adhesive. Humid environments induce an increase in electrical resistance between aluminum objects bonded in this manner. However, joints that are electrically stable through stress testing in environments of elevated temperature and humidity (85°C and 80% RH for up to 137.5 h) have been obtained by treating the aluminum surface with a thin layer (less than 50 Å) of an organo-silane coupling agent, that is, a material capable of bonding chemically with the aluminum oxide surface layer and potentially bonding with the polymer binder in the adhesive. The present study shows that besides their traditional use as surface modifiers for adhesion improvement, organo-silanes can act as corrosion inhibitors of aluminum surfaces to stabilize electrical performance. Whereas other treatments used for preparation of metal surfaces for bonding, using electrically-insulating structural adhesives, typically do not ensure reliable electrical performance, minimal and reproducible increase in resistance has been observed for joints prepared using the procedure described here. Application of this method does not require any significant investment in equipment and the surface pretreatment of the metal surface is quite simple.     

Roll‐to‐Roll Cohesive,Coated, Flexible,High‐Efficiency Polymer Light‐Emitting Diodes Utilizing ITO‐Free Polymer Anodes

This paper reports solution‐processed, high‐efficiency polymer light‐emitting diodes fabricated by a new type of roll‐to‐roll coating method under ambient air conditions. A noble roll‐to‐roll cohesive coating system utilizes only natural gravity and the surface tension of the solution to flow out from the capillary to the surface of the substrate. Because this mechanism uses a minimally cohesive solution, the roll‐to‐roll cohesive coating can effectively realize an ultra‐thin film thickness for the electron injection layer. In addition, the roll‐to‐roll cohesive coating enables the fabrication of a thicker polymer anode film more than 250 nm at one time by modification of the surface energy and without wasting the solution. It is observed that the standard sheet resistance deviation of the polymer anode is only 2.32 Ω/□ over 50 000 bending cycles. The standard sheet resistance deviation of the polymer anode in the different bending angles (0 to 180°) is 0.313 Ω/□, but the case of the ITO‐PET is 104.93 Ω/□. The average surface roughness of the polymer anode measured by atomic force microscopy is only 1.06 nm. Because the surface of the polymer anode has a better quality, the leakage current of the polymer light‐emitting diodes (PLEDs) using the polymer anode is much lower than that using the ITO‐PET substrate. The luminous power efficiency of the two devices is 4.13 lm/W for the polymer anode and 3.21 lm/W for the ITO‐PET. Consequently, the PLEDs made by using the polymer anode exhibited 28% enhanced performance because the polymer anode represents not only a higher transparency than the ITO‐PET in the wavelength of 560 nm but also greatly reduced roughness. The optimized the maximum current efficiency and power efficiency of the device show around 6.1 cd/A and 5.1 lm/W, respectively, which is comparable to the case of using the ITO‐glass.     

A Neural-Network Method of Predicting Defect Formation on the Surface of Thin ITO Films under Mechanical Load

A method for determining the number of defects arising under compressive and tensile stress in bended thin transparent conducting coatings on polymer substrates is proposed. This algorithm is based on the use of mathematical methods of artificial neural networks. The network is trained for calculating the average defect density per unit length at the input parameters corresponding to film and substrate sizes, surface resistance of the conducting coating, and bending radius. The application of this method allows one to determine the average defect density with high accuracy.     

Microwave conductivity of very thin graphene and metal films

The surface resistance of Ag, Au and A1 thin conducting films deposited on low loss dielectric substrates at microwave frequencies using TE011 mode single post-dielectric resonator (10-13.22 GHz) was measured to calculate their conductivity in relation to layers thickness. This method enabling measurements near metal-insulator percolation transition was also applied for epitaxial graphene deposited on semi-insulating SiC. Moreover, effective microwave conductivity has been determined for intentionally made aluminum island structure where the DC conductivity is equal to zero. Special attention was paid to films thickness measurements which is critical for accuracy of sheet resistance calculation. Conductivity of thin metal layers and very thin graphene was compared.     

Efficient fabrication of highly conductive and transparent carbon nanotube thin films on polymer substrates

This paper reports an efficient solution dip coating method for the fabrication of highly transparent and conductive single-walled carbon nanotubes (SWCNTs) based thin films. The key to achieve this is properly preparing the polymer surfaces. In this paper we report a surface pretreatment approach of combining air plasma treatment and silane water solution rinsing for polyethylene terephthalate substrate. After this surface pretreatment, one dip (using a home-made dip coater) of SWCNT solution can yield a thin film of the sheet resistance less than 100 ohms/square (Ω/□) and transparency around 90% at the wavelength of 550 nm; while two dips can produce a thin film of the sheet resistance less than 80 Ω/□ and transparency around 80% at the wavelength of 550 nm. The carbon nanotube thin film performances achieved are close to those of the ITO coatings reported in the literature and the process developed is suitable for both mass production and lab sample preparations.     

离子注入技术改性聚合物薄膜的研究进展

离子注入技术改性聚合物薄膜在电子及电器工程中有着巨大的潜在应用价值。综述了近年来聚合物薄膜经离子注入后在导电性能、光学性能、导磁性能及表面力学机械性能等方面的最新进展。分析了注入离子与聚合物相互作用的物理过程,并指出了该领域存在的问题及发展方向。     

Voltage distribution of two thin polymeric film surface resistancemeasurement systems

Two different methods for measuring the surface resistance of thin polymeric films are presented. The first method is the standard method and utilizes concentric ring metal electrodes. The second one is a novel method and uses instead concentric cylindrical metal electrodes. Both have been studied analytically and experimentally. The voltage distributions that are developed in both methods are calculated, plotted using three-dimensional graphs, and finally compared in order to analyze the advantages and disadvantages of the two measuring systems (acetate is the dielectric). The cylindrical electrodes, which give lower stresses around the outer electrode, seem to be more suitable for the measurements of the surface resistance of thin polymeric films     

高分子辅助沉积法制备LaNiO3外延导电薄膜

近年来LaNiO₃(LNO)作为铁电超晶格、超导异质结和催化剂材料引起了广泛关注。本研究采用简便、低成本的高分子辅助沉积法(Polymer Assisted Deposition, PAD), 在(001)取向的SrTiO₃(STO)单晶衬底上制备了导电性能优异的LNO外延薄膜, 并对其进行各种结构和电学表征。摇摆曲线半高宽为0.38°, 表明LNO薄膜结晶度良好。高分辨XRD的φ扫描进一步证实LNO薄膜在STO衬底上异质外延生长。原位变温XRD测试进一步表征了LNO薄膜的外延生长过程。结果表明, 聚合物分解之后金属阳离子在单晶基体上有序释放并外延结晶。XPS结果表明, 采用PAD制备的LaNiO₃薄膜不存在氧空位。薄膜表面光滑, 粗糙度为0.67 nm。在10~300 K温度区间内的变温电阻率表明LNO薄膜具有良好的导电性能。上述结果表明：PAD制备的LaNiO₃薄膜具有较好的综合性能, PAD在制备外延功能薄膜材料方面具有很大的潜力。     

Properties of indium tin oxide thin films prepared on the oxygen plasma-treated polycarbonate substrate

We prepared the indium tin oxide thin (ITO) film on the polymer substrate by using facing target sputtering method. To obtain a smooth surface of the ITO thin film for application of OLEDs, before deposition of the ITO thin film, the polymer substrate was given plasma surface treatment. The electrical and surface properties were measured by a Hall Effect measurement and a contact angle measurement. The structural and optical properties were evaluated by an X-ray diffractometer, an atomic force microscope and a UV/VIS spectrometer, respectively. All ITO thin films deposited on plasma-treated polymer substrate showed an average transmittance over 85% in visible range, and the lowest resistivity was 4.17 × 10^− 4 Ω cm.     

Fabrication of metal nanostructures by atomic force microscopy nanomachining and related applications

In this work, the fabrication of metal nanostructures by a combination of atomic force microscopy nanomachining on a thin polymer resist, metal coating and lift-off is presented. Nanodots with sizes down to 20 nm and nanowires with widths ranging between 40 and 100 nm have been successfully created by nanoindenting and nanoscratching. The results exemplify the feasibility and effectiveness of the present technique as an alternative to e-beam lithography. The localized surface plasmon resonance properties of the fabricated nanostructures are characterized. The chemical sensing capability of a single nanowire based on resistance increase is also demonstrated.     

AZ31镁合金表面气相沉积不锈钢薄膜的实验研究

利用真空蒸发镀膜技术在镁合金表面沉积不锈钢薄膜是提高镁合金防腐性能的新尝试.本研究利用该技术在AZ31上成功制备了不锈钢薄膜.通过在5%NaCl溶液中的浸入实验和极化实验考察了腐蚀性能,发现镀膜后耐蚀性显著降低.另外,镀膜后的显微硬度也未有明显提高.利用AFM,SEM,EDX等分析手段对薄膜进行了观察和检测,发现耐蚀性变差的原因主要是薄膜表面存在贯穿性的微米级孔洞和Cr元素分布不均匀造成的.     

Measurement of the surface resistance of a metallic thin film at awavelength of 10.6 μm

A quasi-optical method for measuring the surface resistance of a metallic thin film is described. This resistance is derived from measurements of the forward tilt of a surface wave which propagates on the thin metallic film. In order to verify the results, ellipsometry is used. The measurements were made at a wavelength of 10.6 μm at ambient temperature. The surface resistance of an Au film was measured to be 16 times higher than the classical surface resistance     

3D characterization of microstructured poly(methacrylic acid) thin films via Mach-Zehnder interference microscopy

We demonstrate the adaption of a further developed Mach-Zehnder interference (MZI) microscope for the rapid 3D characterization of transparent microstructured polymer thin films. In order to quantify the accuracy of the Mach-Zehnder interferometer, comparative film thickness measurements of photolithographically patterned poly(methacrylic acid) polymer brushes are performed employing two alternative techniques: white light profilometry (WIM) and atomic force microscopy (AFM). When the refractive index of the polymer brushes is calculated from MZI data, we obtain a good agreement with results received from an independent method (ellipsometry).In contrast to surface probing techniques such as AFM or WIM, Mach-Zehnder interferometry is a transmitted light method that measures both surface height profiles and refractive index distributions. MZI thus enables the quantification of film homogeneity with respect to height and density variations at the lateral resolution of a refraction limited microscope. We conclude that MZI is an adequate tool for the rapid and non-destructive characterization of structured polymer thin films. This method should be particularly useful for production quality control of microstructured polymer thin films which possess great potential in electronic device fabrication and biotechnology.     

The influence of core properties on the perforation resistance of sandwich structures – An experimental study

The aim of this study is to investigate the perforation resistance of a range of foam-based sandwich structures. Nine foams, based on a crosslinked PVC, a linear PVC and PET, have been combined with thin glass fibre reinforced plastic skins to produce a range of lightweight sandwich structures, Initially, the mechanical properties of the different foams are characterised. Here, a new test geometry is used to evaluate the toughness characteristics and strengths of the foams under shear loading, a condition similar to that encountered during the impact perforation event.The influence of the plastic collapse stress of the foam in determining the failure thresholds of the front and rear composite skins is established. Here, an existing model has been used to successfully predict failure of the top surface composite skin in the sandwich structures. In addition, the force associated with perforating the lightweight core has been shown to be strongly dependent on the shear strength of the polymer foam. Finally, the perforation resistance of the sandwich structure has been shown to be closely linked to the Mode II work of fracture of the foam material. Here a unique relationship has been established between these two parameters, with all of the experimental points lying on one curve.     

Intrinsically stretchable transparent electrodes based on silver-nanowire-crosslinked-polyacrylate composites

Stretchable transparent composites have been synthesized consisting of a silver nanowire (AgNW) network embedded in the surface layer of a crosslinked poly(acrylate) matrix. The interpenetrating networks of AgNWs and the crosslinked polymer matrix lead to high surface conductivity, high transparency, and rubbery elasticity. The presence of carboxylic acid groups on the polymer chains enhances the bonding between AgNWs and the polymer matrix, and further increases the stretchability of the composites. The sheet resistance of the composite electrode increases by only 2.3 times at 50% strain. Repeated stretching to 50% strain and relaxation only causes a small increase of the sheet resistance after 600 cycles. The morphology of the composites during reversible stretching and relaxation has been investigated to expound the conductivity changes.     

In situ strain monitoring of fiber-reinforced polymers using embedded piezoresistive nanocomposites

Fiber-reinforced polymer (FRP) structures and components are highly susceptible to damage due to delamination, matrix cracking, inter-laminar fracture, and debonding, all of which have potential to cause catastrophic structural failure. While numerous sensing technologies have been developed and embedded in FRP composites for monitoring strain, they serve as defects and can promote damage formation and propagation. Thus, in this study, an alternative technique is proposed for in situ strain monitoring of FRP composites via layer-by-layer multi-walled carbon nanotube-polyelectrolyte thin films deposited directly upon glass fiber weaves. To date, these carbon nanotube-based thin films have been validated for their piezoresistivity. The objective of this study is to characterize the strain sensing performance of different thickness thin films deposited on glass fiber weaves and embedded in FRP specimens using time-domain two-point probe resistance and frequency-domain electrical impedance spectroscopy (EIS) measurements. From the experimental thin film electromechanical response, a new method for fitting using a cubic smoothing spline is implemented and is compared to linear least-squares fitting. The results show that the cubic spline fit is better suited for capturing the strain sensitivities (or gage factors) of these thin films within the time- and frequency-domains along with the variation of strain sensitivity with applied strain. The bulk resistance response is described by the DC resistance measurements, whereas the EIS measurements provide insight of the inter-nanotube response.