Analytical electron microscopy of thin films and interfaces

In this paper a brief overview is presented of some of the techniques available with transmission electron microscopy (TEM) to characterize thin films and interfaces. The critical role that sample preparation plays is discussed. Examples of the application of many of the analytical techniques used in TEM are given. These include nano area electron diffraction, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy. High resolution imaging is available at atomic resolution and new methods are being developed to analyze the images including computer simulation. Imaging of magnetic domains is important to the study of materials used in digital data storage.     

A new method of producing thin films

A new method is proposed for the deposition of thin films using a pulsed supersonic molecular beam seeded with molecules of the material being deposited, and a comparison is made between this method and the conventional one. Taking as an example the unique properties of thin fullerene films obtained experimentally by this method, it is concluded that this method is potentially useful for depositing films of various materials. Pis’ma Zh. Tekh. Fiz. 24, 20–23 (May 26, 1998)     

银基透明导电多层膜界面研究进展

由于具有较低的电阻率和成本、较好的机械加工性能、设计上的灵活性,可室温沉积等优点,银基透明导电多层膜已广泛应用于低辐射膜、强电磁屏蔽、低功耗光电子器件特别是柔性电子器件等领域.但由于材料自身的性质与制备条件的差异性,实际制备的金属/电介质(或半导体)透明导电多层膜界面处往往存在表面等离子体共振、界面导电电子散射、膜层脱...     

Spectroellipsometric method for process monitoring semiconductor thin films and interfaces

Real-time monitoring by multiwavelength phase-modulated ellipsometry of the growth of plasma-deposited microcrystalline silicon (muc-Si) is presented. We discuss the construction of a growth model for process monitoring, and, in particular, we treat the inhomogeneity in the muc-Si layer by using an approximation of the reflection coefficient known as the WKBJ method. By also using the Bruggeman effective medium theory to describe the optical properties of muc-Si, we demonstrate monitoring the crystallinity in the upper and the lower part of the layer together with the thickness. The inversion algorithms thus remain very fast, with calculation times within 5 s on a standard Pentium computer. This makes possible precise control of the thickness and the crystallization of both the top and the bottom interface of the layer during the elaboration of devices such as solar cells and thin-film transistors.     

A method to evaluate mechanical performance of thin transparent films for flexible displays

Mechanical flexing of plastic substrates coated with thin film permeation barriers causes stress-induced cracks that may lead to device degradation. This phenomenon is of particular importance for organic light emitting diodes, an emerging display technology that can be implemented on flexible substrates but imposes stringent requirements on the barrier performance. We demonstrate a dry-etch-based method to highlight cracks in thin films of transparent materials and make them visible under a conventional optical microscope on samples in a neutral, relaxed position. This approach allows for rapid evaluation of the mechanical performance of thin film barriers on flexible substrates.     

Pulsed electron beam deposition of transparent conducting Al-doped ZnO films

Good quality transparent conducting Al-doped ZnO films were deposited on quartz substrates from a high purity target using pulsed electron deposition (PED). Two series of films were made, one deposited at room temperature but at four pressures, viz., 0.7, 1.3, 2.0 and 2.7 Pa of oxygen and one deposited at 1.3 Pa oxygen pressure but at the substrate temperature ranged from room temperature to 600 °C. In order to evaluate the effect of substrate temperature and oxygen pressure on the properties of obtained films, various characterization techniques were employed including X-ray diffraction, stylus profiler, scanning electron microscope, optical spectrophotometer and electrical resistivity. For the first series films, the optimal oxygen pressure of 1.3 Pa was found to bring about the appropriate energetic deposition atoms which results in the best crystallinity. For the second series films, the lowest resistivity was obtained in the film grown at 400 °C. An attempt was made to reduce the resistivity by lowering the oxygen pressure to 0.5 Pa which was the lower limit of working pressure of the PED system. The obtained results indicate that PED is a suitable technique for growing transparent conducting ZnO films.     

A facile UV-curing method for the preparation of transparent and conductive carbon nanotube hybrid films

A new method for preparing flexible, transparent, and conductive multiwalled carbon nanotube (MWCNT) hybrid films with scratch resistance through a facile UV-curing method is described herein. UV-curable urethane oligomers were used as the binder between the MWCNTs and the plastic substrates. The transparency and sheet resistance of MWCNT thin films can be easily tailored by controlling the number of bar coaters. Composite films with different binder ratios were prepared to evaluate and optimize the surface abrasion resistance and adhesion parameter. Two types of MWCNT films, those with a 56% (with a 586 komega/sq sheet resistance) and a 78% transmittance (with a 22 Momega/sq sheet resistance) were obtained using the UV-curable resin, and the conductive films showed distinguished abrasion resistance and good adhesion.     

A novel method for producing of steel tubes with Al foam core

In this study, the aluminum foam filling steel tube was produced by powder metallurgy and cold welding process. By this method, Al powder mixed with 0.6 wt.% TiH₂ powder and then pressed into the steel tube. This filled tube was treated in temperature above aluminum melting point for releasing the hydrogen gas by decomposition of TiH₂ particles for providing of foam production conditions. For the first time, the steel tube with Al foam core produced by this method, without using of binder or fitting. Main advantage of these filled tubes is high energy absorption. Energy absorption is very useful in automobile and railway industry. Lightweight is another advantage of these tubes for these applications. It is found that the Al foam filling steel tubes absorb higher energy with respect to the sum of the energy absorptions of the steel tube and aluminum foam alone.     

High-resolution three-dimensional probes of biomaterials and their interfaces

Interfacial relationships between biomaterials and tissues strongly influence the success of implant materials and their long-term functionality. Owing to the inhomogeneity of biological tissues at an interface, in particular bone tissue, two-dimensional images often lack detail on the interfacial morphological complexity. Furthermore, the increasing use of nanotechnology in the design and production of biomaterials demands characterization techniques on a similar length scale. Electron tomography (ET) can meet these challenges by enabling high-resolution three-dimensional imaging of biomaterial interfaces. In this article, we review the fundamentals of ET and highlight its recent applications in probing the three-dimensional structure of bioceramics and their interfaces, with particular focus on the hydroxyapatite-bone interface, titanium dioxide-bone interface and a mesoporous titania coating for controlled drug release.     

On the structure of indium oxide-tin oxide transparent conducting films by electron diffraction and electron spectroscopy

Thin films of indium oxide-tin oxide mixtures produced by r.f. sputtering have been investigated by transmission electron diffraction and by electron spectroscopy techniques. Both methods support the view that, whereas the indium environment is substantially the same as in the starting material, namely In₂O₃, the environment of the tin is changed towards lower binding energies than the SnO₂ starting material. This is not the case when tin oxide alone is deposited in the same sputtering plant. Annealing at temperatures up to 450°C in both air and forming gas, although altering the resistivity appreciably, did not alter this structure dramatically. There was only an obvious sharpening of the electron diffraction rings.     

A novel high-throughput fatigue testing method for metallic thin films

Abstract

Thin films are used in a wide variety of computing and communication applications although their fatigue behavior and its dependence on alloying elements are not very well known. In this paper, we present an experimental implementation of a novel high-throughput fatigue testing method for metallic thin films. The methodology uses the fact that the surface strain amplitude of a vibrating cantilever decreases linearly from the fixed end to the free end. Therefore, a thin film attached to a vibrating cantilever will experience a gradient of strain and corresponding stress amplitudes along the cantilever. Each cantilever can be used to extract a lifetime diagram by measuring the fatigue-induced damage front that progresses along the cantilever during up to 10⁸ load cycles.     

Spin coating of transparent zinc oxide films using novel precursor

The coating of transparent ZnO films using zinc 2-ethylhexanoate [Zn(OOCH(C₂H₅)C₄H₉)₂] as a novel metal organic monomer is reported. Zinc 2-ethylhexanoate is liquid at room temperature and can be spin-coated on a flat substrate without precipitation of ZnO under ambient condition. The spin-coated films were heated at different temperatures to remove unwanted organic materials from the surface. It was found that transparent ZnO films could be produced on glass substrates at low heating temperature (~400 °C). The ZnO films produced using the new monomer were free of cracks and defects. Also the ZnO films produced using the new monomer have excellent optical transmittance, mechanical properties and small surface roughness. The surface morphology and degree of crystallinity of the films coated by the new monomer were compared with these properties of ZnO films produced using zinc acetate-based sol–gels. The results clearly indicate that the novel monomer is a potential precursor for coating transparent ZnO films at low temperatures.     

A novel high-throughput fatigue testing method for metallic thin films

Thin films are used in a wide variety of computing and communication applications although their fatigue behavior and its dependence on alloying elements are not very well known. In this paper, we present an experimental implementation of a novel high-throughput fatigue testing method for metallic thin films. The methodology uses the fact that the surface strain amplitude of a vibrating cantilever decreases linearly from the fixed end to the free end. Therefore, a thin film attached to a vibrating cantilever will experience a gradient of strain and corresponding stress amplitudes along the cantilever. Each cantilever can be used to extract a lifetime diagram by measuring the fatigue-induced damage front that progresses along the cantilever during up to 10⁸ load cycles.     

A novel method of producing dicadmium stannate in thin film form

The possibility of dicadmium stannate thin film production using a vacuum evaporation technique has been investigated. Thin films produced by this method have been characterized using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), electron diffractometry and analytical scanning electron microscopy (SEM).     

A simple method for studying surface films on solids using transmission electron microscopy

A simple and rapid method for extracting and identifying a small amount of a foreign substance on the surface of a solid using a transmission electron microscope is developed. In this method surface species, such as contaminants, oxides or segregated surface films, are obtained by scraping a solid surface with a small piece of knife edge. The knife edge on which surface films adhere is then directly mounted on a microscope specimen holder for transmission electron microscopy observation. Pieces of surface films accumulated on the knife edge are found to be sufficient in quantity for phase identification using an electron diffraction method. Examples of this simple technique are taken from our recent structural study of gold electrodeposits.     

高雾度透明纤维素薄膜制备、性能及其太阳能电池应用

将可持续的纤维素材料与电子器件结合是当今学术界的研究热点。高雾度透明纤维素薄膜是一种具有特殊光学性能的纸张。它除了具有普通纸张的优点(可降解、成本低、柔性、质轻等)外,还呈现出高的透光率和优异的光散射性能,可作为绿色光学透明材料应用于太阳能电池,提升电池的光电转化效率。本文首先简要介绍了高雾度透明纤维素薄膜的发展历程;接着,详细总结了高雾度透明纤维素薄膜的制备方法及其性能(如光学、力学、热稳定性、耐水等);然后论述了现阶段这类薄膜在太阳能电池中的应用进展;最后,总结了高雾度透明纤维素薄膜存在的科学技术问题,并对其今后的研究方向以及应用前景进行了展望。