Sol-Gel Preparation of Transparent and Conductive Aluminum-Doped Zinc Oxide Films with Highly Preferential Crystal Orientation

Transparent aluminum-doped zinc oxide (ZnO) films were prepared via the sol-gel method on silica-glass substrates from 2-methoxyethanol solutions of zinc acetate and aluminum chloride that contained monoethanolamine. Dip coating was conducted at room temperature, with substrate withdrawal rates of 1.2-7.0 cm/min. After each deposition, the films were heat-treated in air at 200°-450°C for 10 min (pre-heat-treatment). After six to fourteen layers had been deposited, the films were then subjected to annealing in air at 500°-800°C for 1 h (the first post-heat-treatment), followed by annealing in nitrogen at 500°-700°C for 15 min to 4 h (the second post-heat-treatment). All the films obtained were transparent and showed only an extremely sharp ZnO (002) peak in the X-ray diffractometry (XRD) patterns. The effects of the aluminum content, the substrate withdrawal speed, and the heat-treatment conditions on the electrical resistivity of the films were studied. All these factors strongly affected the resistivity. The lowest resistivity value (6.5 10^-3 Omegacm) was achieved in a film that contained 0.5 at.% aluminum, prepared with a low substrate withdrawal speed (1.2 cm/min), and a pre-heat-treatment of individual layer at 400°C in air and a post-heat-treatment of the entire film at 600°C in air, followed by a post-heat-treatment at 600°C in nitrogen. These preparation parameters also affected the degree of crystal orientation, which was revealed by the intensity of the ZnO (002) XRD peak. Higher crystal orientation was effective in reducing the film resistivity, whereas the higher grain-packing density and possible aluminum segregation were thought to have positive and negative effects, respectively, in reducing the resistivity.     

Preparation and properties of novel poly(urethane-imide)s

A series of poly(urethane-imide)s were prepared by a novel approach. Polyurethane (PU) prepolymer was prepared by the reaction of polyester polyol and 2,4-tolylenediisocyanate (2,4-TDI), and then end-capped with phenol. The PU prepolymer was blended with poly(amide acid) or oligo(amide acid) prepared from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and oxydianiline (ODA) at room temperature in various weight ratios. The blend films obtained by casting and then drying were not transparent, suggesting that phase separation occurred between the polyimide (PI) and PU components. The films became transparent, however, after thermal treatment at 100°C and then 200°C for 1 h each, irrespective of the ratio of the two components. The poly(urethane-imide) films showed good solvent-resistance. Dynamic mechanical analysis of the films showed that glass transition temperatures (T_g) shifted depending on the ratio of PI and PU components. This shift of T_g, along with the transparency of the films, suggests that the PU and PI components employed here are miscible to some extent and that domains of each phase by microphase separation are small. Tensile measurement of the blend films from poly(amide acid) showed that the films are plastic or elastic, depending on the ratio of the components. Thermal stability of the PU was found to increase by the incorporation of polyimide component.     

Characteristics of Optimized Al:ZnO sputtering targets prepared by nanostructured powder

Optimized Al:ZnO sputtering target was prepared by cold isostatic pressing (CIP) using nanostructured zinc oxide powder and aluminum oxide powder as raw material. Compared with the target prepared by conventional raw materials, the performance of the optimized Al:ZnO sputtering target is greatly improved. The microstructure of the optimized Al:ZnO sputtering target is refined and its average grain size is less than 5 μm with 99.7% theoretical density. Al:ZnO thin films of both optimized and conventional targets were prepared by RF magnetron sputter and their properties were characterized, respectively. The Al:ZnO thin films obtained by optimized target feature better uniformity and compactness, and the internal stress is −378.8 MPa, which is nearly 2/3 lower than that of the conventional target. The film obtained by optimized targets also features a 97% IR transmittance, 1.71 nm Rq surface roughness and non-offset (002) XRD peak. It can be speculated that the optimized Al:ZnO target has great potential to prepare micrometer scale Al:ZnO films and employed in thin-film ZnO device industry.     

Conductivity and anticorrosion performance of polyaniline/zinc composites: Investigation of zinc particle size and distribution effect

Polyaniline/zinc composites and nanocomposites were prepared using solution mixing method. Zinc (Zn) particles with an average particle size of 60 μm and zinc nanoparticles with an average particle size of 35 nm were used as fillers in polyaniline (PANI) matrix. Films and coatings of PANI/Zn composites and nanocomposites were prepared by the solution casting method. Electrical conductivity and anticorrosion properties of PANI/Zn composite and nanocomposite films and coatings with different zinc loadings were evaluated. According to the results, electrical conductivity and anticorrosion performances of both PANI/Zn composites and nanocomposites were increased by increasing the zinc loading. Also results showed that the PANI/Zn nanocomposite films and coatings have better electrical conductivity and corrosion protection effect on iron coupons compared to that of PANI/Zn composite.     

Work-function engineering of carbon nanotube transparent conductive films

We developed a method that allows control of the work function of carbon nanotube (CNT) transparent conductive films on a flexible sheet of plastic. The approach involves the deposition of small amount of metals, such as aluminum, on CNT transparent conductive films followed by a measure of the work function of the films using in situ ultraviolet photoelectron spectroscopy. Core-level spectra of the films were collected in order to investigate the chemical reaction when a small amount of aluminum was deposited on their surface in a stepwise manner. The measurements revealed that deposition of less than 0.5 nm of aluminum was enough to control the work function of CNT transparent conductive films.     

Preparation of AlN and LiNbO3 thin films on diamond substrates by sputtering method

Diamond is attracting interest as a high velocity material because its elastic constant is the highest of all substances and the surface acoustic wave (SAW) velocity is more than 10 000 m/s. Although diamond is not piezoelectric, its high acoustic propagation makes it a desirable substrate for SAW devices when coupled with piezoelectric thin films such as aluminum nitride (AlN) and lithium niobate (LiNbO₃). Highly oriented AlN thin films and LiNbO₃ thin films were prepared by a reactive sputtering method on polycrystalline diamond substrates. The average surface roughness (Ra) of the AlN thin films was below 2 nm by locating the diamond substrates at the position of 100 mm from the aluminum target. The full width at half maximum of the rocking curve for the AlN(002) peak of X-ray diffraction was approximately 0.2°. SAW characteristics with an interdigital transducer (IDT)/AlN/diamond structure were investigated. The average surface roughness of LiNbO₃ thin films was 5 nm. If the highly oriented LiNbO₃ films are deposited on a diamond substrate, the IDT/LiNbO₃/diamond layered structure will be capable of wide-bandwidth application in SAW devices at high frequencies.     

Sol–Gel Preparation of Thick PZN–PZT Film Using a Diol-Based Solution Containing Polyvinylpyrrolidone for Piezoelectric Applications

Dense and crack-free lead zinc niobate–lead zirconate titanate (PZN–PZT) films were deposited on silicon and glass substrates by spin coating using a sol containing propanediol and polyvinylpyrrolidone. Single-layer PZN–PZT films as thick as 0.80 μm were deposited by a single spin coating with successive heat treatments at 250° and 700°C. After heat treatment, the films were dense, crack free, and optically transparent. In addition, the crystallographic orientation of the thick film was controllable by adjusting the heat-treatment conditions. The ferroelectric properties of the (111)-oriented film were superior to those of the (100)-oriented film. On the other hand, the piezoelectric and dielectric properties of the (100)-oriented film were better than those of the (111)-oriented film. The piezoelectric coefficients ( d ₃₃) of the PZN–PZT films of 4.0-μm-thickness were 192 and 110 pC/N for the (100)-and (111)-oriented films, respectively.     

Development of optically transparent ZnS/poly(vinylpyrrolidone) nanocomposite films with high refractive indices and high Abbe numbers

A series of optically transparent ZnS‐poly(vinylpyrrolidone) (PVP) nanocomposite films with high refractive indices and high Abbe numbers have been prepared. Mercaptoethanol (ME) capped ZnS nanoparticles (NPs) were introduced into the PVP polymer matrix via simple blending with high nanophase contents. ME‐ZnS NPs of around 3 nm were prepared from zinc acetate and thiourea precursors in N,N‐dimethylformamide using ME as a capping agent. Transparent nanocomposite films with high refractive indices and high Abbe numbers can be easily prepared by a conventional film casting method. TGA results indicated that the ZnS/PVP nanocomposite films exhibit good thermal stability and the measured contents of ZnS NPs in the films agree well with the theoretical values. The refractive indices and the Abbe numbers of the ZnS/PVP nanocomposite films range from 1.5061 to 1.7523 and 55.6 to 20.4 with the content of ME‐ZnS NPs varied between 0 and 80 wt %, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal Softening Behavior and Application to Transparent Thick Films of Poly(benzylsilsesquioxane) Particles Prepared by the Sol–Gel Process

Thick films of poly(benzylsilsesquioxane) (BnSiO_3/2) particles, prepared by the sol–gel process, were deposited onto indium-tin-oxide-coated glass substrates by electrophoresis for the application to the micropatterning of the films. BnSiO_3/2 particles were thermally softened and sintered at ∼50°C, which was above the glass transition temperature of the particles. The films prepared by the electrophoretic sol–gel deposition consisted of aggregates of particles with diameters of 0.2–1 μm and were opaque. The film shrank from 2.5 μm to 1.4 μm in thickness and became transparent upon sintering of the particles during heat treatment at temperatures >100°C.     

Synthesis and evaluation of ZSM-5 films on cordierite monoliths

Well-defined ZSM-5 films were prepared on cordierite monoliths using the seed film method. The monoliths were seeded with silicalite-1 seeds and hydrothermally treated either at 75 or at 150 °C in a single or several steps. By adding sodium hydroxide to the solution, the aluminum concentration in the zeolite increased. Consequently, films with different Si/Al ratios were prepared. The film thickness could be controlled from 110 nm to 9 μm. Multi-step synthesis was used to prevent bulk crystallization and ultrasound treatment was found to be beneficial (in order) to remove sedimented crystals on the top of the coatings. The zeolite-coated monoliths were active for p-xylene isomerization, and the test results indicated that the films became less deactivated than the films prepared on alumina beads.     

Conductive and transparent multilayer films for low-temperature TiO2/Ag/SiO2 electrodes by E-beam evaporation with IAD

Conductive and transparent multilayer thin films consisting of three alternating layers (TiO₂/Ag/SiO₂, TAS) have been fabricated for applications as transparent conducting oxides. Metal oxide and metal layers were prepared by electron-beam evaporation with ion-assisted deposition, and the optical and electrical properties of the resulting films as well as their energy bounding characteristics and microstructures were carefully investigated. The optical properties of the obtained TAS material were compared with those of well-known transparent metal oxide glasses such as ZnO/Ag/ZnO, TiO₂/Ag/TiO₂, ZnO/Cu/ZnO, and ZnO/Al/ZnO. The weathering resistance of the TAS film was improved by using a protective SiO₂ film as the uppermost layer. The transmittance spectra and sheet resistance of the material were carefully measured and analyzed as a function of the layer thickness. By properly adjusting the thickness of the metal and dielectric films, a low sheet resistance of 6.5 ohm/sq and a high average transmittance of over 89% in the 400 to 700 nm wavelength regions were achieved. We found that the Ag layer played a significant role in determining the optical and electrical properties of this film.     

Fabrication of highly conducting and transparent graphene films

Graphene-based transparent conducting films were prepared using the following method. A chemically-reduced graphene dispersion was synthesized and graphene films were prepared from it by transfer printing, followed by thermal treatment. The resulting graphene films possessed an excellent electrical conductivity with a high transparency. A sheet resistance lower than ∼2 KΩ/sq and a transparency well over 80% were achieved at a typical wavelength of 550 nm. These properties are considered quite sufficient for many applications, such as transparent conductor films for touch panels.     

Facile synthesis of metal organic decomposition Al-doped ZnO ink for inkjet printing and fabrication of highly transparent conductive film

In this paper, a MOD (Metal organic decomposition) Al doped ZnO (AZO) ink was directly used for inkjet printing transparent and conductive AZO films. The ink was synthesized by using zinc acetate dihydrate and aluminum nitrate nonahydrate as precursor, 1,2-diaminopropane as a complexing agent, ethyl alcohol as solution, ethyl cellulose as addition agent. The thermal decomposition behavior of the MOD ink was investigated. The various MOD AZO inks were inkjet printed and heated at different temperatures for different times. The films were studied by X-ray diffraction, scanning electron microscopy, resistivity measurements and ultraviolet–visible spectroscopy. The results demonstrated that 0.2 M AZO (2 at%) film heated at 250 °C for 120 min showed highly preferential growth along the c-axis, uniform microstructure with a resistivity of 0.03 Ω cm and high transmittance more than 90% in the visible range of the spectrum with an optical band gap at 3.326 eV.     

Low-temperature growth of highly conductive and transparent aluminum-doped ZnO film by ultrasonic-mist deposition

Aluminum-doped ZnO (AZO) thin films are grown by ultrasonic-mist deposition method for the transparent conducting oxides (TCO) applications at low temperatures. The AZO films can be grown at a temperature as low as 200 °C with zinc acetylacetonate and aluminum acetylacetonate sources. The lowest resistivity of grown AZO films is 1.0×10⁻³ Ω·cm and the lowest sheet resistance of 1 μm thick films is 10 Ω/□, which is close to that of commercial indium tin oxide (ITO) or Asahi U-type SnO₂: F glass. The highest carrier concentration and mobility are 5.6×10²⁰ cm⁻³ and 15 cm²/V·sec, respectively. Optical transmittance of the AZO films is found over 75% for all growth conditions. We believe that the properties of grown AZO films in this study are the best among all reported previously elsewhere by solution processes.     

氧化锌铝包覆硼酸钐粉体的制备及性能表征

为了获得具有较低红外发射率和激光反射率的复合材料,通过将氧化锌铝复合于硼酸钐表面的方法,获得了复合效果较好、红外发射率和激光反射率都相对较低的氧化锌铝/硼酸钐纳米复合粒子。用共沉淀法制备了氧化锌铝包覆硼酸钐纳米复合粉体,从包覆前后的电镜照片可以看到包覆层的厚度约为250nm。并且研究了包覆过程中m(硼酸钐):m(氧化锌)、处理硼酸钐所用盐酸的浓度和包覆前驱体的煅烧温度等因素对红外发射率和激光反射率的影响。结果表明,m(硼酸钐):m(氧化锌)为1.5:1、盐酸浓度为0.4mol/L、煅烧温度为650℃时红外发射率和激光反射率最低,最低的红外发射率为0.70、最低的激光反射率为0.73%。     

Dependence of zinc aluminate microscopic structure on its synthesis

Alumina doped with zinc oxide was synthesized by sol–gel method in alcohol solution. Hybrid oxides of aluminum and zinc were prepared from various aluminum precursors (aluminum sec-butoxide, aluminum nitrate, and aluminum isopropoxide) and zinc acetate solution with ethylacetoacetate and nitric acid as a chelating agent and catalyst, respectively. Types and molar ratio of the precursor to the chelating agent and acidic catalyst were found to remarkably affect the formation of transparent sol of aluminium–zinc sol composite. With relatively low temperature of 50 °C, the suitable molar ratio of aluminum sec-butoxide to ethylacetoacetate to nitric acid for preparing the homogeneous sol was 1:0.40:0.86. Furthermore, the calcination at elevated temperature higher than 400 °C would be essential for preparing ZnAl₂O₄ with the face centered cubic microstructure. The primary crystalline size of the synthesized zinc aluminate nanostructure was approximately 20 nm with lattice spacing of 0.55 nm.     

Study of the correlation between flexible food packaging peeling resistance and surface composition for aluminum-metallized BOPP films aged at 60°C

ABSTRACT

This study investigated the correlation between surface composition and peeling resistance in food packaging films by studying the heat aging of fabricated films over varying periods of time. The films consisted of a layer of aluminum (Al) metallized, biaxially oriented polypropylene (BOPP) bonded with a polyurethane (PU) adhesive onto another polymeric layer of low-density polyethylene (LDPE). The Al metallized films were prepared by physical vapor deposition (PVD) and aged at 60°C for either 5 or 15 days. The resulting aluminum surfaces were analyzed using X-ray photoelectron spectroscopy (XPS) and found to contain aluminum oxide (Al₂O₃) and trihydroxide (Al(OH)₃). The XPS characterization also revealed a 29% increase in the Al(OH)₃ layer thickness of the aged sample relative to a non-aged sample. Atomic force microscopy (AFM) was applied on investigations of possible morphology changes. The aluminum and PU adhesive surface energies were also determined using contact angles measurements and the aluminum surface energy was found to increase by as much as 11.7% compared to the non-aged sample, while the PU adhesive surface energy was at least 65% higher than that of the metallic substrate. The peeling resistance of the laminated aluminum was determined by average peel strength measurements and it was found that the variation in peel strength was related to changes in the Al₂O₃ layer thickness. The delaminated samples were analyzed using scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) and showed the cohesive failure of the aluminum film.     

非晶硅太阳能电池背反ZnO:Al薄膜制备

以ZnO:Al(2%Al2O3,质量分数)为靶材,用射频磁控溅射在玻璃衬底上制备ZnO:Al薄膜,分析了各沉积参数对薄膜光电性能的影响。结果表明:溅射功率对ZnO:Al的透过率影响最大,其次是反应腔室压力,而衬底温度对透过率几乎没有影响。ZnO:Al的电阻率主要取决于衬底温度和溅射功率。综合考虑透过率和电阻率,确定了背反ZnO:Al的最佳沉积参数(衬底温度为200℃,溅射功率为200W,反应腔室压力为0.6Pa),得到了透过率大于85%,电阻率最小为7.6×10-4Ωcm的ZnO:Al薄膜。制备了ZnO:Al/Ag/ss(stainless steel)背反电极,并将其用于非晶硅太阳能电池。与无背反的不锈钢衬底上的电池相比,非晶硅太阳能电池短路电流密度增加了16%。     

Zn对Al_2O_3-Al-C滑板中温性能和显微结构的影响

以板状刚玉、氧化铝微粉、金属铝粉、金属锌粉为主要原料,以酚醛树脂为结合剂,制备Al_2O_3Al-C滑板样品。研究了金属锌粉的引入对Al_2O_3-Al-C滑板显微结构和性能的影响。结果表明:在450～1050℃热处理温度条件下,锌粉的引入改变了滑板中金属铝粉的反应进程,金属锌粉氧化后形成的氧化锌沉积在金属铝粉表面,改变了金属铝粉熔化、扩散和反应的进程,有利于材料在较低温度下形成金属结合,提高中温(600～1100℃)性能。锌粉的引入对材料显微结构有较大影响,900℃热处理3 h后材料内部形成大量颗粒状、柱状和针状氮氧化物,1 050℃热处理3 h后材料内部形成大量碳化铝纤维,有利于材料性能的提高。     

Chemical Solution Deposition of Transparent and Metallic La0.5Sr0.5TiO3+x/2 Films Using Topotactic Reduction

Metallic and transparent La_0.5Sr_0.5TiO_{3+ x /2} films were prepared by the chemical solution deposition (CSD) method using topotactic reduction processing. The use of Si powder as the reducing agent was facile and allowed easy manipulation. It was observed that metallic (resistivity at 300 K ∼2.43 mΩ cm) and transparent (∼80% transmittance at visible light) La_0.5Sr_0.5TiO_{3+ x /2} films could be obtained with an annealing temperature of 900°C, which was significantly lower than the hydrogen reduction temperature (∼1400°C). The successful preparation of metallic and transparent La_0.5Sr_0.5TiO_{3+ x /2} films using CSD has provided a feasible route for depositing other perovskite-structured functional layers on La_0.5Sr_0.5TiO_{3+ x /2} films using this low-cost all CSD method.