Transmission electron microscope specimen preparation of Zn powders using the focused ion beam lift-out technique

Particles of Zn powder have been studied to show that high-quality scanning electron microscope (SEM) and transmission electron microscope (TEM) specimens can be rapidly produced from a site-specific region on a chosen particle by the focused ion beam (FIB) lift-out technique. A TEM specimen approximately 20-μm long by 5-μm wide was milled to electron transparency, extracted from the bulk particle, and micromanipulated onto a carbon coated copper mesh TEM grid. Using the FIB lift-out method, we were able to prepare a site-specific TEM specimen from a difficult material in under 3 hours. The TEM analysis of the lift-out specimen revealed a large amount of thin area free from characteristic signs of damage that may be observed as a result of conventional argon ion milling. The overall microstructure of the specimen prepared by the FIB lift-out method was consistent with samples prepared by conventional metallographic methods. A grain size of ∼10 to 20 μm was observed in all specimens by both TEM and SEM analysis. Light optical microscopy revealed the presence of internal voids in ∼10 to 20 pct of all particles. The SEM analysis showed the voids to extend over ∼70 pct of the particle volume in some cases.     

Prediction of outcome and early vs. late improvement in OCD patients treated with cognitive behaviour therapy and pharmacotherapy

Several factors must be taken into account when deciding which specimen preparation technique(s) to use. These factors include the amount of material available, ease of preparing this material due to its properties and familiarity, location and size of the region of interest, amount of information sought, facilities accessible, and time available by the researcher to devote to the preparation of the specimen. The more popular specimen preparations for thin films, namely, electropolishing, cleaving, crushing, mechanical thinning followed by ion milling, and ultramicrotomy are discussed and the more unusual techniques such as extraction/replication, photochemical etching, lithography and reactive ion etching (RIE), chemically assisted ion beam etching (CAIBE), and precision polishing-based techniques are described. Their advantages and disadvantages in the context of the above factors are discussed. Suggestions for increasing one's success rate in preparing specimens are given. The role of transmission electron microscopy (TEM) analysis is considered since it rarely stands in isolation from other physical analytical techniques, nor is it often used as a quick diagnostic tool. Conservation of material by the minimization of the amount of material used (or destroyed) by TEM specimen preparation, and conservation of one's time by performing TEM analysis only on "worthy" samples should be given maximum consideration.     

Evaluation of Characterization Techniques for Iron Pipe Corrosion Products and Iron Oxide Thin Films

A common problem faced by drinking water studies is that of properly characterizing the corrosion products (CP) in iron pipes or synthetic Fe (hydr)oxides used to simulate the iron pipe used in municipal drinking-water systems. The present work compares the relative applicability of a suite of imaging and analytical techniques for the characterization of CPs and synthetic Fe oxide thin films and provide an overview of the type of data that each instrument can provide as well as their limitations to help researchers and consultants choose the best technique for a given task. Crushed CP from a water distribution system and synthetic Fe oxide thin films formed on glass surfaces were chosen as test samples for this evaluation. The CP and synthetic Fe oxide thin films were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray powder diffractometry (XRD), grazing incident diffractometry (GID), transmission electron microscopy (TEM), selected area electron diffraction, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared, M?ssbauer spectroscopy, Brunauer–Emmett–Teller N2 adsorption and Fe concentration was determined by the ferrozine method. XRD and GID were found to be the most suitable techniques for identification of the mineralogical composition of CP and synthetic Fe oxide thin films, respectively. AFM and a combined ToF-SIMS–AFM approach proved excellent for roughness and depth profiling analysis of synthetic Fe oxide thin films, respectively. Corrosion products were difficult to study by AFM due to their surface roughness, while synthetic Fe oxide thin films resisted most spectroscopic methods due to their limited thickness (118?nm). XPS analysis is not recommended for mixtures of Fe (hydr)oxides due to their spectral similarities. SEM and TEM provided great detail on mineralogical morphology.     

Lattice Defects Diffuse Scattering from Thin Films of a Ge-Si System with Low-Energy Ar+ and Xe+ Bombardment During Molecular Beam Epitaxy (MBE) Growth

Homo?CGe, homo?CSi, and hetero?CSi_0.2Ge_0.8 alloy epitaxial layers, using molecular beam epitaxy (MBE), were grown on Ge and Si (001) substrates in order to study development of crystalline strains caused by ion bombardment during the growth of materials. Ion energies and ion/atom fluxes were used in the epitaxial growth, and significant lattice distortions along the growth direction developed. Using high-resolution X-ray diffraction (HRXRD) and high-resolution transmission electron microscopy (HRTEM), the form of distortion, caused by low-energy argon (Ar⁺) and xenon (Xe⁺) bombardment of the thin epitaxial films grown on the (001) substrates, were investigated. The isotropic point defects case (of spherical distortions) occurs in epitaxial thin films ??as-grown?? processes. The intensity distribution has two maxima, one from the distorted layer and the other from the original unaffected matrix. The significant changes in the 2?? location, peak broadening and integrated intensity from the secondary (004)* reflections were obtained as a function of aging temperatures in the grown layers. Defects-induced diffuse scattering close to and between Bragg reflections supplies information on the strain and symmetry of the distortions fields and yields the atomic structure of point defects (self-interstitial, vacancies, and small clusters). First, aging heat treatment affects the distribution of distortions obtained in local regions at the ??as-grown?? layer, which develops to a special topography of continued distortions at higher aging temperatures. At aging temperatures above 923 K (650 °C), this extra diffraction peak disappears. The TEM observations reveal the appearance of dislocation lines with dark and bright contrasts around them, interdislocation strain contrasts, and disordered point defects atoms in the silicon region with semicoherent interfaces. The ion bombardment-induced formations and injection of the different types of pointlike defects and defects clusters.     

Epitaxy of silicon doped gallium arsenide by molecular beam method

The molecular beam method is a versatile experimental technique which may be used to grow high quality single crystal thin films in the range from 100Å to several microns with precise control of uniformity and thickness. Films may be doped by an additional molecular beam containing the doping material simultaneously impinging on the substrate surface with the film molecular beams. Epitaxial GaAs thin films doped with silicon were grown by the molecular beam method in an ultrahigh vacuum system in which high energy electron diffraction and mass spectrometric measurements could be made during growth or by stopping growth momentarily. The crystallinity and beam intensity parameters of these films were thus studied during growth. The doping profiles and the amount of compensation were evaluated by the Schottky barrier diode method and the photo luminescence spectra.     

Metal/semiconductor interfacial reactions

Vapor phase deposition of thin metal films on semiconductors followed by annealing frequently leads to the nucleation and growth of one or more reaction products in the vicinity of the metal/ semiconductor interface. Often, these products are intermetallic compounds that may be distributed as precipitates in the interfacial region. The composition, size, shape, and areal density of these precipitates may be the major factors in determining the electrical properties of the interface. The semiconductors studied were GaAs, SiC, and semiconducting diamond, while the metals were principally the refractory metals, although several other metals were also investigated. The interfaces of representative samples were examined using Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), including selected area electron diffraction (SAD), and optical metallography. The electrical properties were evaluated by current-potential (I-V) and Hall effect measurements. This paper is based on a presentation made in the “G. Marshall Pound Memorial Symposium on the Kinetics of Phase Transformations” presented as part of the 1990 fall meeting of TMS, October 8–12, 1990, in Detroit, MI, under the auspices of the ASM/MSD Phase Transformations Committee.     

离子束混合过程中Au/Fe磁性膜的巨磁电阻效应在线研究

在离子柬混合和强磁场条件下，在线研究了Au/Fe磁性膜的巨磁电阻效应，发现了不同磁场强度下的离子柬混合对巨磁电阻效应影响的规律，以及不同注入条件对样品饱和磁场的影响。讨论了样品由磁性多层膜逐渐向磁性纳米颗粒膜的转变，以及与此相关的纳米磁性颗粒在磁场作用下的非各向同性生长，并通过高分辨透射电镜(TEM)观察证实了磁性膜样品中磁性纳米Fe颗粒存在各向异性生长现象。通过对室温放置了一年以上的磁性纳米颗粒膜样品的电磁物性测量，证明利用离子柬混合技术制备的纳米颗粒膜在室温具有良好的热稳定性和时间稳定性。     

Interface characterization of epitaxial Ag Films on Si(100) and Si(111) grown by molecular beam epitaxy

Silver films grown on Si(100), Si(111), and thin oxide layers by molecular beam epitaxy (MBE) have been studied using multiple analysis techniques, including X-ray diffraction (pole-figure method and double-crystal diffractometry), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and MeV He⁺ Rutherford backscattering spectrometry (RBS)/ channeling. Despite the large lattice mismatch (～25 pct) between Ag and Si, high-quality Ag single-crystal films (surface minimum yield χ_min = 6 to 10 pct) were grown on clean Si substrates. Ag(111) texture films were also grown on the oxide layers of Si(100) and Si(111) surfaces. The epitaxial Ag/Si interface was thermally stable up to at least 500 °C. The adhesion between Ag and the oxide layer was poor. The primary defects contained in the Ag/Si(111) were twins. The quantity of twinning depends on the film thickness and the substrate orientation. For both Ag/Si(100) and Ag/Si(111) epitaxial systems, a high-density defect region was contained in the Ag film within ～1000 Å of the interface. Silver films grown on misoriented Si(111) substrates (～4 deg off normal) were misoriented by 0. 5 deg toward the surface normal.     

Grain Size and Wettability of TiO2/SiO2 Photocatalytic Composite Thin Films

The uniform transparent TiO2/SiO2 photocatalytic composite thin films are prepared by sol-gel method on the soda lime glass substrates, and characterized by UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), BET surface area, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that the addition of SiO2 to TiO2 thin films can suppress the grain growth of TiO2 crystal, increase the hydroxyl content on the surface of TiO2 films, lower the contact angle for water on TiO2 films and enhance the hydrophilic property of TiO2 films. The super-hydrophilic TiO2/SiO2 photocatalytic composite thin films with the contact angle of 0-° are obtained by the addition of 10%-20% SiO2 in mole fraction.     

Densification of Ni and TiAl by SPS: Kinetics and Microscopic Mechanisms

Densification by spark plasma sintering (SPS) of ductile (Ni) and brittle (TiAl) metallic materials has been studied to elucidate the mechanism of densification in the two cases. Isothermal densification experiments were carried out to determine the activation parameters in Ni. Transmission electron microscopy (TEM) observations of thin foils extracted by focused ion beam (FIB) in the contact regions between particles of TiAl and Ni powders are presented. Macroscopically, the most striking feature observed here is that the densification of Ni takes place in the wide temperature range of 0.2 to 1.0 T_m, whereas that of TiAl varies in the temperature range of 0.7 to 0.9 T_m, which is significantly narrower (T_m being the melting temperature of Ni and the peritectic temperature of TiAl). In Ni, the low activation energy (164 ± 30 kJ/mol), the high dislocation density in the interparticle contact region, and the formation of recovery cells involving dislocation climb indicate that the rate-controlling mechanism is probably self-diffusion in dislocations. In TiAl, high dislocation densities leading to reorganization into subboundaries point to dislocation climb mechanisms, which are kinetically controlled by volume diffusion. The difference in densification kinetics between Ni and TiAl is then accounted for in terms of the difference in their respective rate-controlling mechanisms operative during densification.

     

Characterization of hydroxyapatite film with mixed interface by Ar+ ion beam enhanced deposition

Ar+ ion beam enhanced deposition (IBED) was used to produce a hydroxyapatite (HA) film on polished titanium substrates. In this study, the HA ceramic target was sputtered by an argon-ion beam with an energy of 1.5 KeV, and the sputtered film was intermittently bombarded by energetic argon-ions at 60 KeV. An effective Ca-Ti mixed layer produced by the energetic argon-ion bombardment was confirmed by using Auger electron spectroscopy. The characteristics of the deposited films were evaluated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. XRD analysis revealed that the as-deposited film was amorphous, and a hydroxyapatite-type structure was obtained from the post-heat treatment of the deposited films. SEM observations showed that no distinct difference in surface morphology was found between the as-deposited and heat-treated samples for Ar+ IBED films, suggesting a strongly bonded HA film on the titanium substrate. In comparison with the HA target, some chemistry alterations were brought about in the deposited films, such as the incorporation of CO3, the loss of the OH groups and some distortion of the phosphate lattice.     

单层LB膜诱导化学沉积银膜的研究

以硬脂酸单层LB膜为基底 ,利用膜亲水端基的诱导作用 ,通过化学沉积法制备了金属银膜。扫描电镜(SEM)观察到银膜表面由直径 2 0 0nm左右的银粒子构成 ,透射电镜 (TEM)分析表明银膜为面心立方结构 ,并对单层LB膜上化学沉积银的机理进行了探讨     

半绝缘砷化镓(SI-GaAs)单晶中的微缺陷的研究

砷化镓(GaAs)为第二代半导体材料，GaAs衬底质量直接影响器件性能。利用JEM-2002透射电子显微镜(TEM)及其主要附件X射线能量散射谱仪(EDXA)，对半绝缘砷化镓(SI-GaAa)单晶中微缺陷进行了研究。发现SI-GaAa单晶中的微缺陷包含有富镓沉淀、富砷沉淀、砷沉淀、GaAa多晶颗粒和小位错回线等。还分析了微缺陷的形成机制。     

In situ study of amorphous to crystalline transition in indium oxide thin films using transmission electron microscopy

We have studied reactively evaporated thin films of amorphous indium oxide by HREM and have attempted to observe the structural changes appearing during the course of crystallization as the films are irradiated with electron beam. Two kinds of process are observed for crystallization: (i) gradual ordering over the whole of the projected area leading to crystallization with no obvious nucleation event, and (ii) nucleation and growth process.     

Lattice Distortion Formations by Low-Energy Ar<Superscript>+</Superscript> Bombardment of Thin Silicon Films Grown on Silicon (100)

The transmission electron microscopy (TEM) and X-ray characterization of lattice distortion forms caused by low-energy Ar⁺ bombardment of grown thin silicon films on a silicon (001) substrate were studied. The isotropic case (of spherical distortions) takes place in epitaxial silicon “as grown” processes. The intensity distribution consists of two maxima—one from the distorted layer and the other from the original unaffected silicon lattice. Significant changes in the 2θ location, peak broadening, and integrated intensity from the (004)* reflections were obtained as functions of aging temperatures. First, aging heat treatment, affects the distribution of distortions obtained from local regions at the “as grown” layer, which changes to a special topography of continued distortions at higher aging temperatures. At aging temperatures above 923 K (650 °C), this extra diffraction peak disappears. The TEM observations reveal the appearance of dislocation lines with dark and bright contrasts around the lines and interdislocation strain contrasts and disorder of Ar atoms in Si matrix regions with coherent interfaces.     

The Morphology of Tensile Failure in Tantalum

The deformation, crack nucleation, coalescence, and rupture process of pure tantalum (99.9 pct) were studied under room temperature quasistatic loading using several in situ and ex-situ techniques including optical metallography, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission-electron microscopy (TEM). The fracture surface of tantalum forms a ridge-and-valley morphology that is distinct from conventional notions of ductile dimple microvoid coalescence, and also distinct from spall damage formed during dynamic shock conditions. Failure proceeds by void nucleation at a dislocation cell wall or in subgrain interiors. Coalescence appears to involve a two-stage damage progression: first individual voids coalesce along the tensile axis forming diamond-shaped multivoid cavities; then cavities link-up by intercavity necking. Final rupture occurs when the intercavity necks thin to ~100-nm films and fail by crystallographic cleavage. This final tearing process was observed using in situ TEM tensile deformation of a thin tantalum film. The detailed microstructural and morphological observations of the current study can be used to guide the development of improved models for tearing of ductile metals.     

Humidity sensing properties of La^3＋ and K^＋ co-doped Ti0.9Sn0.1O2 thin films

The humidity sensing properties of La3+ and K+ co-doped Ti0.9Sn0.1O2 thin films were investigated. The humidity sensitive thin films were prepared by sol-gel method on alumina substrates. The sensing behaviors of thin films were inspected at different sintering temperatures by constructing a humidity-impedance measuring system. It was found that the addition of rare earth ion La3+ and alkali ion K+ was beneficial for improving the humidity sensitive properties of the samples and La0.003K0.5Ti0.9Sn0.1O2 sintered at 500 ℃ for 4 h showed the best humidity sensing properties. The impedance of this thin film decreased from 109 to 104 Ω with excellent linearity in the humidity range of 11%-95%. Narrow hysteresis loop, prominent stability and high sensitivity were obtained. The effects of dopant con-tent and doping mechanism on humidity sensitivity were also discussed in terms of segregation of rare earth ions at grain boundaries and granularity of crystalline and influence of K+ on the decrease in the intrinsic resistance of the materials, and increase in the number of wa-ter adsorption sites.     

高速火焰喷涂WC-Co飞行粒子与涂层的物相分析

本文用高速火焰喷涂方法(HVOF)对WC-Co粉末进行喷涂,采用水冷法对喷涂中的飞行粒子进行收集,并以45#钢为基体制备了相应涂层。采用聚焦离子束(FIB)切割的方法,分别制备了粉末、飞行粒子和涂层的薄片状透射电镜样品。采用能谱检测了样品中各元素的分布情况,选区电子衍射法鉴定了样品中的物相。结果表明,W和C元素在喷涂过程中向Co基体中扩散,在冷却过程中与Co形成非晶相。η相在WC颗粒的边缘形成。     

Preparation of La MnO_3/graphene thin films and their photocatalytic activity

A novel photocatalyst of La MnO3/graphene thin films with the perovskite-type was synthesized by sol-gel process assisted with spin-coating methods on glass substrates.The prepared samples were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Brumauer-Emmett-Teller(BET) surface area analyzer, X-ray photoelectron spectroscopy(XPS) and UV-vis diffuse reflectance spectroscopy.Results showed that after the introduction of graphene, the perovskite structure was unchanged and the size of La MnO3 particles was about 22 nm, which uniformed growth in graphene sheet.Determination of contact angle indicated that the contact angle of glass substrate decreased and the hydrophilicity improved after treating with H2SO4 and APTES.The UV-Vis photocatalytic activity of the photocatalysts was evaluated by the degradation of diamine green B.La MnO3/graphene thin films had better photocatalytic ability than La MnO3 and Ti O2 films.The obtained k was 0.5627 and 0.3441 h–1 corresponding to La MnO3/graphene films and Ti O2 films, respectively.     

Flame spray synthesis of nano lanthanum strontium manganite for solid oxide fuel cell applications

Lanthanum strontium manganite is a classic cathode material for solid oxide fuel cells (SOFC). Nanosized LSM particles, due to their higher specfic surface area, have been found to enhance the electrode performance by providing a larger three phase boundary (TPB) area. However conventional processes like solid state, sol-gel or co-precipitation, produce particles having low specic surface area (< 8 m²/g) and hence require high sintering temperatures. Moreover these processes are multi-step and are hence time consuming. In the present work, single phase LSM with a crystallite size of 26 nm and a specfic surface area as high as 40 m²/g was produced by a flame spray pyrolysis method. The as-synthesized powder was characterized by X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Porous thin films were prepared by spin coating a water based dispersion of LSM. Electrochemical performance of the nanoparticulate cathode films were studied using impedance spectroscopy. Interfacial polarization resistance value of as low as 0.085 Ωcm ² at 850°C was obtained by this method. This method thus offers a very cost effective approach for the preparation of highly active cathode thin films for SOFC applications.