Analysis of thermal diffusivity of Ti thin film by thermoreflectance and periodic heating technique

Thermal diffusivity of Ti thin film with several hundred nanometers thickness has been measured by means of thermoreflectance (TR) technique and periodic heating using front heating and front detection configuration. Ti thin films were prepared on Si substrates by dc sputtering method. Then thin Mo layers as reflection layers were coated on Ti thin films. Surface of the Mo layer is irradiated by sinusoidally intensity modulated heating laser. Temperature response at the heated area is measured by a probe laser beam with constant intensity, as a TR signal. Phase lag between the phase of TR signal and that of heating laser beam was obtained from 100 kHz to 2.6 MHz. To analyze thermal diffusivity of Ti thin films using the phase lag data, we developed a three-layer analytical model such as Mo coating (100 nm)∕thin film∕semi-infinite substrate. The calculated phase lag using analytical model is in good agreement with the experimental data for the whole frequency range. The thermal diffusivity of two Ti thin films is determined to be 5 × 10(-6) m(2)∕s, which is 53% of the bulk one.     

Phospholipid,Nature's own slide and cover slip for cryo-electron microscopy

Thin films of surface-active compounds, with or without particulate material, can be obtained by immersing and withdrawing a bare specimen grid from a solution/suspension of the compound. Immediately after withdrawing the grid, thinning of the film starts. Thinning is initially powered by gravity and capillary forces and will proceed in thin films (< 100 nm) driven by intermolecular forces until the London-van der Waals attractive forces come to an equilibrium with electrostatic repulsion of similarly charged surfaces of the film. With small unilamellar vesicles prepared from the phospholipid dimyristoyl phosphatidyl choline (DMPC) the draining behaviour of these films was studied by cryo-electron microscopy. Small unilamellar vesicles were observed within the film as well as the coalescence of these vesicles into sheets (‘leaky’ membrane fusion). Sheets dominate the images when films are allowed to drain for longer periods (>3min). Thin films were formed on grids from catalase crystals suspended in a DMPC suspension and vitrified by cooling. High-resolution information was obtained by electron diffraction at low temperature and under low-dose conditions from catalase crystals surrounded by small vesicles as well as from catalase crystals surrounded by sheets of DMPC. In the latter case the water content drops from 99% (DMPC in small vesicles) to less than 30% (DMPC in sheets) during draining. Ferritin was added to a DMPC suspension and thin films were prepared and vitrified. After prolonged draining ferritin molecules were deposited in layers with a stepwise increase in thickness. Draining of thin films has thus a dehydrating effect as well as a sorting and ordering effect. These effects must be considered when using surface-active compounds at air-water interfaces as a slide and cover slip for electron microscopy.     

Modelling and experimental investigations of thin filmsof Mg phosphorus‐doped tungsten bronzes obtainedby ultrasonic spray pyrolysis

In this study, the synthesis of thin films of Mg phosphorus doped tungsten bronzes (MgPTB; MgHPW₁₂O₄₀·29H₂O) by the self‐assembly of nano‐structured particles of MgPTB obtained using the ultrasonic spray pyrolysis method was investigated. As the precursor, MgPTB, prepared by the ionic exchange method, was used. Nano‐structured particles of MgPTB were obtained using the ultrasonic spray pyrolysis method. The nano‐structure of the particles used as the building blocks in the MgPTB thin film were investigated experimentally and theoretically, applying the model given in this article. The obtained data for the mean particle size and their size distribution show a high degree of agreement. These previously tailored particles used for the preparation of thin films during the next synthesis step, by their self‐assembly over slow deposition on a silica glass substrate, show how it is possible to create thin MgPTB films under advance projected conditions of the applied physical fields with a fully determined nanostructure of their building block particles, with a relatively small roughness and unique physical properties.     

Advances in thick and thin film analysis using interferometry

The use of interferometry to measure transparent and semi-transparent films is becoming more and more important as understanding of the measurement becomes more widespread. Techniques for measurement of thick films of 1 μm or greater using interferometry have been available for some time but measurement of thin films using interferometry is a much newer technique, also the effect of films coatings on interferometry measurements in general is now becoming more widely understood. The measurement of thick and thin films using interferometry is discussed in this paper.     

Thin film thickness measurements in two phase annular flows using ultrasonic pulse echo techniques

The electric power generation and oil/gas production industries have a strong interest in the physical characterization of conducting and non-conducting liquid films that are formed during the flow of liquids in pipes. Conducting and non-conducting liquid films do not lend themselves to the same characterization techniques due to the different requirements originating from their electrical properties. Techniques based on the use of ultrasound are extremely attractive for that purpose as they do not depend on the electrical properties of the liquid and are also non-invasive. This paper presents the application of ultrasonic techniques for measuring the thickness of wavy thin liquid films (<6 mm) in vertical pipes. Initial benchtop experiments were performed, and different signal processing methods were implemented in order to identify the most suitable depending on the film thickness. For a film thickness >0.5 mm a time of flight method was utilized whereas for a film thicknesses <0.5 mm a frequency method and time domain method were utilized. These methods were validated using a theoretical volume measurement on a static system. The studied methods were then tested on downward and upward vertical flow experimental rigs with pipe diameters of 127 mm and 34.5 mm respectively. The results of the experiments using ultrasonic methods showed good agreement with the measurements obtained using a multi pin film sensor and a concentric conductance probe, highlighting the potential that ultrasound offers in thin film measurements.     

Photoconductive imaging in a photon scanning tunnelling microscope capable of point-contact current sensing using a conductive fibre probe

A photoconductive photon scanning tunnelling microscope was developed to investigate the point-contact photoconductive properties of condensed matter. In order to detect the current and the optical signal at a local point on a surface, we coated the edge of a bent type fibre probe with indium tin oxide. Thus it was possible to measure both photocurrent and optical property with subwavelength resolution. The performance of the novel microscope was evaluated by analysing an organic thin film of copper phthalocyanine (CuPc), which is known to be an efficient photoconductive material. Photocurrent and current–voltage characteristics were observed at the local point on the CuPc thin films. Furthermore, photoconductive images were obtained with topography and near-field optical imaging using this system. The photoconductive PSTM shows potential in various areas of future optics and electronics.     

Design of a physical vapor transport cell for time controlled deposition of nucleation phase organic thin films

A portable high vacuum chamber has been designed to implement a solenoid operated shutter used as a substrate cache during short duration deposition of organic thin films via the physical vapor transport (PVT) method. This PVT cell was designed for the study of gravity effects on nucleation phase organic thin films obtained in laboratory unit g conditions and especially low g conditions found onboard parabolic flights. The design challenges met were, notably, the timely control of deposition on the substrate during parabolas and maintenance of the experimental cell pressure during operation of the shutter. Nucleation phase thin films of the organic hole transporting semiconductor N,N' -bis(3-methylphenyl)-N,N' -bis(phenyl)benzidine (TPD), obtained with the use of the PVT cells, show that the moving shutter has an effect on the convective PVT gas flow; however, as convection is reduced, this effect is observed to be equally reduced.     

High resolution electron microscopy of some carbonaceous materials

The image contrast of extremely thin films of amorphous carbonaceous materials has been studied experimentally using thin supporting films of single crystal graphite. The use of thin specimens reduces the ‘overlap’ effect in imaging amorphous materials. Image contrast of their images was therefore interpreted by the ‘projected potential approximation’. Single sheets of graphitic carbon crystal were imaged with c perpendicular to the beam and their image details were compared with those of the amorphous carbon films. This comparison demonstrated that amorphous carbon films prepared by evaporation contained microcrystalline regions having graphitic structure.     

基于多分辨SVD包和MED的柔性薄壁轴承故障特征提取与诊断

柔性薄壁轴承安装到谐波减速器上时内外圈会受迫变形成椭圆,工作过程中会产生周期性的冲击信号,使得柔性薄壁轴承的故障特征信号提取变得更加复杂。为实现对柔性薄壁轴承故障特征信号的有效提取,提出了一种基于多分辨奇异值分解（SVD）包和最小熵解卷积（MED）的柔性薄壁轴承故障特征提取与诊断的方法。利用多分辨SVD包对采集到的振动信号进行分解,分解后选用前4层中信噪比最高的近似信号进行MED冲击特征提取处理,将处理后的信号与前4层的细节信号进行信号重构和频谱分析,得到故障特征频率,最后将得到的故障特征频率与理论计算值进行对比,判断出故障类型。和单独使用多分辨SVD包处理的实验效果相比,该方法对柔性薄壁轴承的故障特征提取效果更好。     

SnSe2薄膜的载流子与声子动力学研究

基于自建的超快抽运探测实验系统,研究了化学气相沉积法生长的SnSe₂薄膜的超快载流子与声子动力学。对SnSe₂薄膜随抽运能量密度变化的载流子弛豫过程的测量结果表明该薄膜具有超快的载流子热化过程和皮秒至纳秒时间尺度的复合过程。伴随着光生载流子的超快激发和能量弛豫,SnSe₂薄膜发生晶格热化,产生了特定频率的相干声学声子。通过分析声学声子振荡信号随抽运能量密度变化的规律,揭示了SnSe₂薄膜产生的相干声学声子的特性。研究结果对SnSe₂薄膜在光电器件领域的应用研究具有一定的参考价值。     

基于Nano Indenter的纳米刻划性能试验研究

概述了纳米划痕试验在研究材料纳米刻划性能方面的研究进展，着重介绍了材料刻划破裂机理和刻划临界载荷，以及薄膜材料厚度效应和基底效应对纳米刻划性能的影响等方面的研究状况，讨论了今后尚需进一步研究的问题。     

Nanotopographic characterization of spotted micro arrays on polyvinyl alcohol films by high‐resolution long‐range nanoprofiling

The nanopositioning and nanomeasuring machine was applied for the nanotopographic characterization of polymer micro spot arrays of fluorimetric chemochips. Chemochips are arrays of fluorescence dyes in a hydrogel matrix with different response behaviors of chemical components determination of chemical and physico‐chemical properties of analytes by a pattern recognition approach. For the characterization and quality control of the spots, a nanometer resolution is needed over a scan range of several millimeters. This challenge could be met by use of a scanning probe sensor in connection with a laser interferometer controlled high‐precision positioning and measuring device. This way, topographic scans with the resolution of atomic force microscope could be achieved over these demandingly large ranges. The technique was used in order to determine the quality of thin film micro spots made from fluorescence dye solutions on preformed polymer films and also tested for characterization of monomolecular films in the form of micro spots. The nanotopographic measurements reflect the strong influence of solvent/matrix interaction, wetting, swelling and material transport during the application of picoliter droplets in the spotting process. The measurement clarifies the reason for the formation of roughness in the nanometer range by nano‐crystal formation in the upper part of polymer film and the rim formation of micro spots during solvent evaporation. The studies show the effect of application of different numbers of droplets in a dispensing series for spot formation and prove the high importance of polymer/solvent interaction for the quality of formed micro spots as well as for spot arrays of monomolecular films. SCANNING 31: 35–48, 2009. © 2009 Wiley Periodicals, Inc.     

Morphology selection for cupric oxide thin films by electrodeposition

Polycrystalline cupric oxide thin films were deposited using alkaline solution bath employing cathodic electrodeposition method. The thin films were electrodeposited at various solution pH. The surface morphology and elemental analyzes of the films were studied using scanning electron microscopy (SEM) and energy dispersive X-ray analysis, respectively. SEM studies revealed that the surface morphology could be tailored suitably by adjusting the pH value during deposition. Mesh average on multiple lattice mode atomic force microscopy image was obtained and reported.     

Near-field radiation of bow-tie antennas and apertures at optical frequencies

We investigate the ability of the bow‐tie slot antenna to generate intense optical spots below the diffraction limit. A commercially available finite‐difference time‐domain electromagnetic modelling software is used in the numerical simulations. The finite‐difference time‐domain software is first compared to analytical results at optical frequencies to verify its accuracy. We then present numerical simulations for various geometries involving apertures on thin films and the bow‐tie antenna. The transmission efficiency and optical spot size of the bow‐tie antenna are compared with those of rectangular and circular apertures on thin metal films. We also investigate the effects of material composition, frequency, and antenna geometry on the near‐field radiation pattern using numerical simulations.     

Characterization of nitride thin films by electron backscatter diffraction

Thin films incorporating GaN, InGaN and AlGaN are presently arousing considerable excitement because of their suitability for UV and visible light‐emitting diodes and laser diodes. However, because of the lattice mismatch between presently used substrates and epitaxial nitride thin films, the films are of variable quality. In this paper we describe our preliminary studies of nitride thin films using electron backscattered diffraction (EBSD). We show that the EBSD technique may be used to reveal the relative orientation of an epitaxial thin film with respect to its substrate (a 90° rotation between a GaN epitaxial thin film and its sapphire substrate is observed) and to determine its tilt (a GaN thin film was found to be tilted by 13 ± 1° towards [101 0]_GaN), where the tilt is due to the inclination of the sapphire substrate (cut off‐axis by 10° from (0001)_sapphire towards (101 0)_sapphire). We compare EBSD patterns obtained from As‐doped GaN films grown by plasma‐assisted molecular beam epitaxy (PA‐MBE) with low and high As₄ flux, respectively. Higher As₄ flux results in sharper, better defined patterns, this observation is consistent with the improved surface morphology observed in AFM studies. Finally, we show that more detail can be discerned in EBSD patterns from GaN thin films when samples are cooled.     

Thickness determination of ultra-thin films using backscattered electron spectra of a new toroidal electrostatic spectrometer

Backscattered electron spectroscopy offers detailed information for multilayer and subsurface-layer materials with distinct Z contrast: It can be used for the validation of Monte Carlo calculations, to obtain depth selective electron microtomographic images, and to determine the thickness of ultra thin films on bulk substrates. In this paper we describe a new energy-dispersive method for thickness determination of thin films on bulk aluminum using backscattered electron (BSE) spectra obtained by a polar, toroidal, electrostatic spectrometer. After a brief recapitulation of the spectrometer's geometry, the techniques for its energy calibration and the preparation of thin double-layer films are introduced. Backscattered electron measurements and thickness calibrations for Au and Cu films with thicknesses of 0–200 nm on bulk aluminum will be presented for various primary electron energies.     

超声波检测焊点质量的建模方法及应用分析

介绍了两层板焊接时焊点的有限元建模方法：通过金相实验得到焊点尺寸参数,利用超声检测的回波衰减理论及超声波传播衰减信号得到焊点阻尼系数。首先建立了材料为BLD的两层板多类型焊点有限元模型,然后通过与设备检测对比的方法验证了模型的准确性,最后研究了探头在曲面检测工况下角度定位的灵敏度问题,并通过实验进行了验证,实验结果表明：对曲面焊点质量进行检测时,探头角度偏离法线10°范围内,检测结果受到的影响很小。     

Current-sensing scanning near-field optical microscopy using a metal probe for nanometre-scale observation of electrochromic films

A novel technique for scanning near‐field optical microscopy capable of point‐contact current‐sensing was developed in order to investigate the nanometre‐scale optical and electrical properties of electrochromic materials. An apertureless bent‐metal probe was fabricated in order to detect optical and current signals at a local point on the electrochromic films. The near‐field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p‐polarized laser illumination. With regard to electrical properties, current signal could be detected with the metal probe connected to a high‐sensitive current amplifier. Using the current‐sensing scanning near‐field optical microscopy, the surface topography, optical and current images of coloured WO₃ thin films were observed simultaneously. Furthermore, nanometre‐scale electrochromic modification of local bleaching could be performed using the current‐sensing scanning near‐field optical microscopy. The current‐sensing scanning near‐field optical microscopy has potential use in various fields of nanometre‐scale optoelectronics.     

Evaluation of several common standards for the X-ray microanalysis of thin biological specimens

The question of the best type of standard to use for X-ray microanalysis of thin biological specimens remains unanswered. Standards embedded in an organic matrix have the advantage that they resemble biological specimens, but their composition is generally not known exactly. We compared several standards and, surprisingly, inorganic binary salts sprayed onto a supporting film were the most suitable: they corresponded closely with several other methods using organic matrices; they were easily produced; and their composition is known. Glutaraldehydeurea aminoplastic resin thin sections and thin films containing dissolved salts were problematic. The composition of the polymer appears to be variable, and the thin films did not correspond with any other standard tested. Chelex¹⁰⁰ bio-standard beads and flakes loaded with accurately determined concentrations of ions, embedded in epoxy resin and thin sectioned, tended to correspond to the results obtained with the binary salts. However, the results from some bio-standards were inexplicably aberrant. An epoxy resin standard was used for bromine, and was found to agree closely with the binary standards.     

类金刚石薄膜微观摩擦性能的FFM评价——针尖尺度效应

采用等离子体增强气相沉积制备了类金刚石薄膜，利用原子力显微镜的轻敲模式观察了它们的形貌，并在考虑外加载荷和扫描速度的基础上，用摩擦力显微镜（FFM）对比考察了尖端探针和平头探针对类金刚石薄膜摩擦性能评价的影响。结果表明：类金刚石薄膜的表面粗糙度随基底负偏压的增加而减小；存在于探针和类金刚石薄膜之间的水膜对尖端探针的剪切阻力贡献较大，且尖端探针测得的摩擦力变化趋势受扫描速度影响显著；水膜对平头探针起着不同形式的润滑作用，从而导致平头探针和类金刚石薄膜之间摩擦性能的速度效应存在差异；利用摩擦力显微镜考察类金刚石薄膜的摩擦性能时，存在着明显的针尖尺寸效应。