Drying dynamics of polymers films by an interferometric technique

We analyze a simple laser reflectivity measurement as a tool to monitor the drying kinetics of transparent polymer films. The reflectivity signal of a laser beam at normal incidence shows oscillations due to interference arising from multiple reflection of the laser light within the drying film. We develop a model to interpret the reflectivity curves in terms of time evolving refractive indices at the top and bottom of the film. We present results of the drying kinetics of transparent alkyd films on a glass substrate of high refractive index. Data shows a clear hallmark indicating the evolution of the crosslinking process. From the reflectivity curves, the time evolution of the refractive indices at the top and bottom is obtained. Assuming a linear-gradient of the refractive index along the depth of the film the average refractive index and consequently the film thickness as a function of time are estimated. Clear features in the time evolution of the refractive indices and thickness, correlate well with qualitative “dust”, “touch” and “fingerprint” drying times. Additionally, we present some preliminary results for water based latex binders, where scattering of light is present, showing that this simple optical technique could be extended for studying latex film formation.     

Quantifying Water at the Organic Film/Hydroxylated Substrate Interface

A method, based on Fourier transform infrared-multiple internal reflection (FTIR-MIR) spectroscopy, for determining the amount and thickness of water at an organic film/hydroxylated substrate interface has been developed. The analysis uses a two-layered model, which takes into account: 1) water at the organic film/hydroxylated substrate interface, 2) water taken up by the organic film within the penetration depth of the evanescent wave and 3) change of the penetration depth as water displaces the organic film from the substrate. Experimentally, the method requires the application of an organic film, transparent or opaque, of sufficient thickness on a hydroxylated internal reflection element, which is used as the substrate. A water chamber is attached to the organic-coated specimen. After adding water to the chamber, FTIR-MIR spectra are taken automatically at specified time intervals without disturbing the specimen or the instrument. Water uptake in the organic films and FTIR-MIR spectra of water on the substrates are also obtained and used for the analysis. Results of examples of three organic films: a clear epoxy, an unmodified asphalt, and a pigmented ester, on a hydroxylated SiO₂-Si substrate were presented to demonstrate the method. The water layer at the interface for the ester and asphalt specimens was found to be much thicker than that for the epoxy, and this was attributed to the presence of a water-sensitive layer accumulated at the interface for the formers. The method should be equally applicable to studies of organic and inorganic compounds at the organic film/hydroxylated substrate interface and their transport rates through films adhered to a substrate.     

A Spectroscopic Technique for Studies of Water Transport Along the Interface and Hydrolytic Stability of Polymer/Substrate Systems

Information on water transport along the polymer/substrate interface is valuable for understanding the mechanisms and the controlling factors affecting the water-induced adhesion loss of polymer-coated metals, adhesive-bonded joints, and polymer/fiber composites subjected to aqueous environments. This paper presents data to demonstrate the capability of a technique, which combines a vertical cell with Fourier transform infrared spectroscopy in the multiple internal reflection mode, for studying water transport along the polymer/substrate interface and interfacial hydrolytic stability of polymeric composites and systems exposed to water and high relative humidities. The technique can distinguish water transport through the film from that along the interface; the latter transport is predominant for polymer/untreated substrate systems. Spectroscopic analyses of fractured surfaces of poor and well-bonded polymer/substrate systems after water exposure indicate that the technique is capable of discerning a hydrolytically-stable interface from a water-susceptible interface.     

Effect of grain orientation on the morphology, dielectric breakdown and optical behaviour of anodic film formed on Al–2wt%Cu binary alloy

Barrier-type anodic film growth on an Al–2wt%Cu alloy is shown to be dependent upon the crystallographic orientation of the substrate grains. Generally, on grains of orientations near [1 0 0], featureless amorphous films, with parallel film/electrolyte and alloy/film interfaces, are formed. Conversely, on grains of orientations near [1 1 0] and [1 1 1], anodic films with occluded oxygen-filled voids of different shape, size and population density, and with undulating film/electrolyte and alloy/film interfaces, are generated. It is also revealed that the population density of dielectric breakdown craters of the anodic film is dependent on the crystallographic orientation of substrate grains. Further, the anodized Al–Cu alloy shows a grain orientation dependent coloured appearance. The colouring arises from interference and unbalanced reflection of certain wavelengths of light caused by the thin anodic films of different morphologies.     

In situ measurement of water at the organic coating/substrate interface

In situ and quantitative information on the water layer at the organic coating/substrate interface is crucial for understanding and preventing the failure of organic coating systems. A technique, based on a two-layer model derived rigorously from internal reflection theory, has been developed for measuring in situ the thickness and amount of the water layer at the organic coating/substrate interface. The technique gives new insight into the processes by which water degrades the coating/substrate bonds. In this technique, a transparent or an opaque organic coating of sufficient thickness is applied to an internal reflection element (IRE) with or without a thin metallic film, which is used as the substrate. A water chamber is attached to the organic-coated specimen. After adding water to the chamber, Fourier transform infrared-multiple internal reflection (FTIR-MIR) spectra are taken automatically at specified time intervals without disturbing the specimens or the instrument. Water uptake in the coating and FTIR-MIR spectra of water on the coating-free substrate are also used for the analysis. Examples of clear and pigmented coatings on untreated and treated substrate surfaces are given to demonstrate the technique. Results of water accumulation at the coating/iron interface with and without applied electrical potentials are given. In addition to measuring water at the coating/substrate interface, the technique provides a means for studying the transport of water through a coating adhered to a substrate. Information on water at the interface and its transport properties through coatings applied to a substrate is valuable for interpreting corrosion, blistering and delamination of organic coating systems, and for developing models for use in predicting the serivce lives of protective coatings.     

PbZr0.4Ti0.6O3-Based Reflectors with Tunable Peak Wavelengths

Based on the phase separation, a series of quasiperiodic PbZr_0.4Ti_0.6O₃ (PZT) multilayers consisting of the ordered alignment of the dense PZT and porous PZT layers have been grown using one single precursor. The multilayers exhibit good performance as a dielectric mirror, and the position of the reflection maximum can be easily tuned over the whole visible range through varying the spinning rate. More than 86% optical reflectivity and less than 19 nm photonic stop-band width have been achieved at room temperature. The quasiperiodic PZT multilayers can be used as dielectric reflectors, interference filters, and optical cavities.     

VTD法制备不同基底倾角的硒化锑薄膜及太阳电池

硒化锑(Sb₂Se₃)具有较高丰度及良好的光电特性,是当前热门太阳电池材料之一。目前,在Sb₂Se₃的多种制备方法中,气相转移沉积法(VTD)因工艺简单且可大面积制备而备受关注。采用VTD法制备Sb₂Se₃薄膜的影响因素有多种,如腔体气压、反应温度、蒸发源与衬底的位置以及生长角度等。本文利用VTD法以不同的生长角度(30°、45°、60°、90°)制备了Sb₂Se₃薄膜,对其进行XRD、Raman、SEM、近红外-紫外反射表征。结果表明不同生长角度对薄膜的结构以及光学特性具有明显的影响。晶粒尺寸随着生长角度的增加而先增大后减小,同时薄膜的形貌由棒状生长转变为片状生长,在基底倾角为90°时,薄膜变得最为致密。近红外-紫外反射光谱表明倾角60°的样品在波长小于1 100 nm的范围具有最低的反射率,在该角度下制备的FTO/CdS/Sb₂Se₃/C器件获得了2.38%的转换效率。     

Surface and interface morphology and structure of amorphous carbon thin and multilayer films

We review the implementation of X-ray reflection (reflectivity and scattering) techniques for the study of amorphous Carbon (a-C, a-C:H, ta-C) thin and multilayer films and in particular in the determination of the film density and surface and interface morphology, which are intrinsically significant for ultra-thin films. We present studies of various a-C and a-C:H films, which include in particular: i) the morphology of a-C/Si interface, ii) the surface morphology and density evolution during sputter growth of a-C, iii) the morphology of the sp²-rich a-C/sp³-rich a-C interfaces in multilayer a-C films, iv) the universal correlation between the film density and the refractive index of a-C and a-C:H films. We also compare and validate the experimental results with relative results from Monte-Carlo simulations within an empirical potential scheme. The computational results shed light on the atomistic mechanisms determining the structure and morphology of the a-C interfaces between individual sp²- and sp³-rich a-C layers and between a-C and Si substrates.     

Formation of Titania Submicrometer Patterns by the Combination of Synthesis from an Aqueous Solution and Transcription of a Resist Pattern

A CrN–coated silicon wafer printed with a resist pattern was used as a substrate, and a novel method for forming titania (TiO₂) patterns was investigated. A TiO₂ thin film formed over the whole surface of the substrate by soaking in a mixed solution of (NH₄)₂TiF₆ and B₂O₃ at room temperature. The resist material then was dissolved off, using acetone, together with the TiO₂ formed on it. A minute pattern of the TiO₂ thin film, transcribing the resist pattern, formed. The minimum line width of the TiO₂ thin film was 300 nm, which was also the minimum line width of the resist pattern.     

Interface structure of photonic multilayers prepared by plasma enhanced chemical vapor deposition

The structures of substrate/layer, layer/layer, and layer/air interfaces in optical multilayers made using plasma enhanced chemical vapor deposition (PECVD) have been probed for the first time using X-ray reflectivity and neutron reflectivity. From the point of view of optical applications the interfaces are extremely sharp, sharper than is often achievable with the self-assembly of block copolymers or deposition techniques in which the polymer layers contact while in a fluid state. The average interface width, a_I, between layers made from different precursors is about 40 Å (16 Å rms). The layer/layer interfaces are generally 2-3 times broader than the layer/air interfaces. Polymeric fluorocarbon films deposited on a Si substrate using PECVD with octafluorocyclobutane (OFCB) monomer show uniform scattering length density with depth except for a region of molecular thickness immediately adjacent to the substrate. Films made from deuterated benzene show uniform density throughout the film thickness.     

Monitoring of film formation,curing and ageing of coatings by an ultrasonic reflection method

During film formation, curing and ageing of coatings changes in physical properties and chemistry of the material occur. For these processes, complex interactions of different factors have to be taken into account. In order to get a more detailed insight in mechanisms of film formation, curing and ageing, it is desired to monitor the changes of the mechanical properties in real time. Therefore, in this work various modifications of an ultrasonic reflection technique enabling such analyses are described.The ultrasonic method measures the complex acoustic reflection coefficient at the interface between a substrate and a coating for longitudinal and/or transversal waves at ultrasonic frequencies. From the complex acoustic reflection coefficients and the density of the sample, the corresponding mechanical moduli and the Poisson ratio can be calculated. The method can be considered as a real time dynamic mechanical analysis at high frequencies. Physical changes as vitrification, swelling and drying, crack initiation and delamination can be monitored. Recently, the ultrasonic reflection technique has been combined with near-infrared analysis for monitoring UV-induced curing reactions within seconds.     

Quantitative analysis on the adsorbed amount and structural characteristics of spin self-assembled multilayer films

In this study, we demonstrate that the adsorbed amount of respective layers in spin self-assembled multilayer films can be controlled and predictable using an empirical power-law equation in terms of spin speed and initial solution concentration. The amount of a pair of polyelectrolytes deposited per bilayer rapidly increases with increasing polyelectrolyte concentration up to 12.5 mM while the solution concentration above 16 mM has no appreciable effect on the adsorbed amount. The adsorbed film thickness per bilayer is shown to be easily controlled from about 5 to 40 Å and proportional to constant power exponents of −0.34 and 0.78 with respect to the spinning speed (Ω) and the mole concentration of polyelectrolytes, respectively. We also demonstrate with synchrotron X-ray reflectivity measurement that the alternating organic/inorganic ultrathin films fabricated by the spin self-assembly process contain highly ordered internal structure and retain unique optical characteristics determined by the boundary condition at both the substrate/multilayer film interface as well as the multilayer/air interface.     

POM匀胶托盘的优化设计

以广泛应用于旋涂功能薄膜工艺中的聚甲醛(POM)匀胶托盘为研究对象,基于数值仿真及实验研究,对现有POM托盘工作中的缺陷进行了分析,结果表明,螺旋托盘基片因发生翘曲形变而易使胶体渗入匀胶机,腔式托盘基片形变量过大。基于分析结果,对现有匀胶托盘进行了优化,提出一种腔式花洒型托盘,其通过过盈配合,在腔式托盘上装配花洒型端盖,数值模拟结果表明,腔式花洒型托盘在保持腔式托盘阻胶结构的基础上,基片最大形变量为2.7μm,与螺旋托盘相比降低了3.9μm左右,且基片边缘处的翘曲形变较小,为0.17μm左右;借助3D打印技术,对优化的托盘进行快速成型制造,并进行了实验分析,实验结果表明,基片形变测量值与数值模拟值变化规律吻合,相同位置的形变值误差最大为9.8%左右,说明仿真结果可靠。     

准显微光度计问题的分析

介绍了显微光度计与准显微光度计的区别。光度计视域光栏系统是显微光度计的重要组成部分,它提供了垂直平行入射光束的必要条件,其锁定的测量限区使被测镜质组等反射光不受周围不同物质反射光的干扰影响,保证了镜质组反射率的真实性与正确性。准显微光度计缺失了光度计视域光栏系统,不能提供垂直平行的入射光束,不具有锁定被测镜质组和干酪根不受周围组分光线干扰的功能,所测反射率不具有客观真实性。     

Specular X-ray reflectivity analysis of adhesion interface-dependent density profiles in nanometer-scale siloxane-based liquid films

Nanometer-scale thick liquid films of poly(methylhydro-dimethyl)siloxane copolymer (PMDMS) deposited on hydrophilic and hydrophobic solid organic films have been studied using synchrotron X-ray specular reflectivity (XRR). The physico-chemical properties of liquid PMDMS at the interfacial level are controlled by the nature of the solid surface. Detailed analysis of the XRR-data revealed the formation of a low-density region in the liquid PMDMS film in the vicinity of the hydrophobic surface, whereas a densely packed molecular layer is formed at the liquid PMDMS-hydrophilic substrate interface. Non-covalent polymer chains are ‘frozen’ at the solid-liquid interfaces in the confined liquid films and interactions with the substrate surfaces (i.e. hydrogen bonding) are responsible for distinctly different density profiles.     

Grazing incidence X-ray diffraction studies on the structures of polyurethane films and their effects on adhesion to Al substrates

Grazing incidence X-ray diffraction was carried out to analyze the structure of polyurethane films as a function of X-ray penetration depth by varying the angle of incidence. Coherence lengths, interplanar spacings, and crystallinities were obtained for non-aged and aged films of OH numbers of 120, 375, and 600 bonded to an aluminum substrate. Aging led to the improvement of bulk crystallinity of all the samples, particularly in the case of the aged PU-375 film, for which a dramatic increase of the bond strength was observed. The crystallinity of non-aged samples varied from the air/polymer surface down to the polymer/aluminum interface. Invariance of coherence length from air surface to interface was observed for PU-120 and PU-375 samples, implying that substrate-induced ordering has little effect on the average crystallite size. As the X-ray penetration increases near the polymer/Al interface, interplanar spacing of (021) reflection in all the films approach the value found for a bulk polyurethane-urea by Ishihara et al. The bond strength of the polyurethane film to the aluminum was exponentially proportional to the crystallinity including the crystalline interphase formed near the substrate. It is also found that the polymer film containing more (100) planes provided higher bond strength.     

Study on Spectral Selective Manipulation Characteristics of Surface Multilevel Micro–Nano Structures by FDTD Simulation

The optical filter based on the micro–nano structure on the material surface is an important optical device, which is widely used in many fields. The filter is fabricated on the substrate with different shapes and sizes of micro–nano array structure, and the wavelength selectivity is realized by adjusting the processing parameters. In this paper, the finite-difference time-domain (FDTD) method is used to simulate the spectral properties of periodic array structures on the Au surface, and the spectral response characteristics of different surface structural parameters to the incident light are obtained. The simulation results show that the periodic pore array has a directional modulation function on the reflectivity and transmittance of the material surface. In the same circular aperture array structure, the wavelength selection ability is proportional to the interval distance of the array period, but the transmission peak linewidth decreases with the increase of the interval distance. The structural spectrum of the cylindrical array is closely related to the structural period. The period of the array structure increases in proportion, the center wavelengths of the reflection and transmission peak of the spectrum are red-shifted. When the height of the array structure increases proportionally, the positions of the center wavelengths of the reflection and transmission peak remain almost unchanged. When the period of the array structure increases, the center wavelength of the reflection and transmission peaks appear red-shifted, and the line width is also narrowed. For the periodic ring array structure, as the inner diameter increases, the reflection peak is significantly red-shifted, and the smaller the ring width, the faster the red-shift of the reflection peak with the wavelength. By controlling the ratio of inner diameter-to-outer diameter, the spectral characteristics of the structured surface can be effectively controlled. These simulation results provide a basis for the preparation of optical filters in the future and a new idea for the study of micro–nano characteristic structures on the surface of materials.     

Changes in the adhesion strength between copper thin films and polyimide substrates after heat treatment

The adhesion strength between a copper (Cu) thin film and a polyimide [pyromellitic dianhydride-oxydianiline (PMDA-ODA)] substrate is reduced by heat treatment at 150°C in air. In this work, we determined the changes in adhesion strength between Cu films and polyimide substrates using Auger electron spectroscopy (AES), attenuated total reflection Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The analysis showed that the weak boundary layer (WBL) shifted towards the Cu interface as the heat treatment time was increased. To confirm this shift, we looked at two other polyimide substrates: biphenyl dianhydride-p-phenylene diamine (BPDA-PDA) and biphenyl dianhydride-oxydianiline (BPDA-ODA). Comparing the adhesion strength for the Cu thin film, the adhesion strength was high for the Cu/PMDA-ODA and Cu/BPDA-ODA laminates, but very low for the Cu/BPDA-PDA laminate. One of the possible reasons for this behavior could be that the ether moiety between the two benzene rings in ODA is related to the adhesion between a Cu film and an 0₂-plasma-treated polyimide (PI) substrate. The relationship between the adhesion strength and chemical bonding states is also discussed. We conclude that a Cu thin film sputtered onto a PI substrate is apt to peel at the oxidized interface, due to the heat treatment.     

Effects of Thermal Annealing on the Structure of Ferroelectric Thin Films

The effects of thermal annealing on the structure of polycrystalline Pb(Zr_0.3Ti_0.7)O₃ (PZT) ferroelectric thin films prepared by chemical solution deposition on Pt/TiO _x electrode stacks were studied using scanning electron microscopy, transmission electron microscopy (TEM), and grazing incidence X-ray specular and diffuse reflectivity of synchrotron radiation. The stratified multilayered structure and element diffusions in the sample were characterized by TEM. Global statistical structural parameters including the density, surface or interface roughness and thickness of each layer in the samples were obtained from fitting the X-ray specular reflectivity using a homogeneous stratified multilayer model of PZT/Pt/TiO _x /SiO₂. The results showed that the PZT surface and PZT/Pt interface roughness changed slightly during thermal annealing in oxygen at 700°C. By contrast, the density increase of the PZT ceramic and density decrease of the Pt-bottom electrode during annealing were observed. A high density value of the PZT ceramic film after the annealing was found, up to 99.8% of the theoretical value of the corresponding bulk ceramics. The density changes of the PZT and Pt layers were further confirmed by X-ray diffuse reflectivity. The influences of the annealing treatment on the density changes of the PZT and Pt layers were attributed to the further densification of the PZT ceramic and incorporation of light elements such as Zr, Ti and O from the neighboring layers into the Pt layer, respectively, as discussed in correlation with the TEM analyses.     

Effect of wax on the adhesion strength between acrylic urethane film and chromated steel sheet,and the friction coefficient of the film

The effect of wax in an acrylic urethane (AU) film on the adhesion strength between AU film and steel sheet treated with Zn-Ni and chromium was investigated by varying the amount of wax using a pull-off test. The adhesion strength decreased as the amount of wax increased. Since the wax in the AU film can react with the reactive functional groups of imine ester (hardener), the cohesive strength of the AU film can be reduced. The distribution of wax in the AU film on a polar and a nonpolar substrate, whose contact angles with water were 30° and 75°, respectively, was examined using contact angle measurements and X-ray photoelectron spectroscopy (XPS). The distribution of wax in the AU film was greatly affected by the degree of polarity of the substrate. In the case of the nonpolar substrate, the wax in the AU film migrated towards the film/nonpolar substrate interface to form a weak boundary layer, where the failure occurred. In the case of the polar substrate, the amount of wax at the film/polar substrate interface was much smaller than that at the film/nonpolar substrate interface and increased linearly with increasing wax content in the AU film. The friction coefficient of the AU film against chromated steel sheet was also measured with varying amounts of imine-ester and additives such as wax and colloidal silica. The friction coefficient appears to be influenced only by the amount of wax.