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Iron-filled multi-walled carbon nanotubes (Fe@MWCNTs) were surface functionalized with various functionalities via a rapid, single-step process involving ultrasonication assisted and microwave-induced radical polymerization reactions. Both hydrophobic (e.g., polystyrenes and polymethyl methacrylate) and hydrophilic (e.g., polyacrylamide, polyacrylic acids, and polyallyl alcohols) polymer chains can be chemically grafted onto the surface of MWCNTs by the same process within ∼10 min. The surface grafted polymers were identified by FTIR, TGA, TEM, EELS and Raman spectra. The solubilities of the surface derivatized MWCNTs are in the range of 1200–2800 mg/l in solutions. The polyacrylic acids modified iron filled MWCNTs have a saturated magnetic dipole moment of ∼40 emu/g at room temperature with a coerceive field of nearly zero gauss.

Diluted magnetic semiconductor Zn1−xCoxO (x≤0.11) nanowires with average diameter of ~40 nm were prepared by thermal evaporation, followed by high-energy Co ion implantation. Bombardment by Co ions produced a good number of structural defects (stacking faults and orientational variations) in the nanowires. The as-implanted nanowires were paramagnetic. We performed two types of thermal annealing, one in 1 atm argon flow and the other in a high vacuum, at 600 °C, and studied the effects of annealing on the magnetic properties of these nanowires. Argon annealing removed structural defects in the nanowires and the nanowires then revealed ferromagnetic ordering. This result suggests that structure defects are harmful to the occurrence of ferromagnetism in the Co-implanted ZnO. The structure of the as-implanted and the annealed nanowires was inspected in detail by using scanning electron microscopy, energy dispersive x-ray spectroscopy, maps of electron energy loss spectra, x-ray diffraction, and high-resolution transmission electron microscopy. Taken together, these studies suggested that no second phase existed on the scale down to the spatial resolution of ~0.5 nm. Noticeably, the nanowires even displayed largely enhanced ferromagnetism after annealing in a high vacuum. A subsequent annealing in oxygen has also been performed on those vacuum-annealed nanowires to study the roles played by the O vacancies in determining the ferromagnetic properties of the nanowires. Our results indicate that both the improved structural quality and the increased number of O vacancies are key factors for the occurrence of ferromagnetic ordering in the Zn1−xCoxO nanowires.

Vanadium oxide nanowires were prepared successfully by thermal evaporation onto ITO-coated glass at a pressure of 8 × 1 0 - 4 Torr and 650 °C from vanadium oxide powders (V 2 O 5 99.95%). The vanadium oxide nanowires-based electrochromic device (ECD) provides larger reaction surface area than thin film-based ECD to store more ions as working or counter electrode. Structure, morphological, and electrochromic properties were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammograms (CV), and UV-VIS spectroscopy. The diameter of vanadium oxide nanowires range from 10 to 100 nm and length up to several hundreds nanometers. The morphology and performance of vanadium oxide nanowires did not alter after 1000 reox-cycles observed by SEM and CV.

A simple method was developed to fabricate tungsten oxide (WO3−x) nanowires based electrochromic devices. The WO3−x nanowires are grown directly from tungsten oxide powders in a tube furnace. The WO3−x nanowires have diameters ranging from 30 to 70 nm and lengths up to several micrometers. The WO3−x nanowires based device has short bleach-coloration transition time and can be grown on a large scale directly onto an ITO-coated glass that makes it potential in many electrochromic applications. The structure, morphology, and composition of the WO3−x nanowires were characterized using the scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy-dispersive spectrometer. The optical and electrochromic performance of the nanowires layer under lithium intercalation was studied in detail by UV–VIS–NIR spectroscope and cyclic voltameter.

We report here the observations and analysis of defects and domain structures in SBA-16 mesoporous films on molecular level using high resolution transmission electron microscopy. The films were made by dip-coating and have layered structure. Domain boundaries both perpendicular and parallel to the substrate were observed. It was found that while some observed low angle and high angle domain boundaries are similar to that found in normal crystals, distortions analogue to that existing in liquid crystal were also observed. The results are shown to provide useful information for understanding the growth mechanism and the properties of the film.

The MBE growth technique is employed to the intensively studied high κ gate dielectrics HfO2 (κ=20) and its alloy (Hf–Al)O2 in replacing conventional SiO2 for nano-CMOS applications. Typical 4.9 nm thick HfO2 films showed low leakage current density of ∼0.4 A/cm2 at 1 V, a dielectric constant κ of 20.7 and an EOT of 0.9 nm. Minor frequency dispersion is observed at C–V curves and is removed by an improved two-frequency method. An epitaxial order of (1 0 0) cubic HfO2 oxide is observed for the depositions on GaAs(1 0 0) at temperatures over 230 °C.

Co-doped ZnO samples with above-room-temperature Curie point were fabricated by the standard solid-state reaction method. Ferromagnetic behavior varied with different quenching temperatures ranging from 1173 K to 573 K after calcination. Extensive analyses on structural and composition revealed that cobalt is homogeneously incorporated into the ZnO lattice forming solid solution instead of precipitation when x ≤ 0.02 in Zn1–xCoxO. In the case of Zn0.98Co0.02O, ferromagnetism was enhanced by decreasing the quenching temperature until 573 K. The coercive field measured by a vibrating sample magnetometer (VSM) at room temperature is around 60–80 Oe. The implication of the effect of quenching temperature in bulk Zn0.98Co0.02O is also discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The formation of helium bubbles in the advanced SiC composites, Tyranno-SA SiC/PyC/β-SiC (TSA) and Hi-Nicalon Type-S SiC/PyC/β-SiC (HNS), implanted with helium and irradiated by dual-beam was investigated. Post-implantation annealing was carried out at 1000/1200/1400 °C, and dual-beam irradiation at 800/1000 °C. For He implantation, helium bubbles were observed only in the SiC matrix for annealing temperatures ⩾1200 °C. For dual-beam irradiation, no He bubbles were observed for a dose of 10 dpa, but for doses up to 100 dpa, He bubbles were observed in the matrix. Under these irradiation conditions, the TSA and HNS fibers exhibited good microstructural stability against helium influence. In addition, possible diffusion modes were suggested here to describe the diffusion behavior of helium in SiC in different temperature regions.

In order to clarify the fracture mechanism of frictional stress and bonding strength in SiC/SiC composites, the mechanical test and HRTEM equipped with electron energy loss spectrometer were used. Due to the high sensitivity of carbon k-edge in the EELS spectrum, EELS is more convenient than other analytical tools. The advanced electronic spectroscopic image (ESI) technique is applied to observe the wide area around the interface of SiC fiber/pyrolytic carbon/SiC matrix. The sp2 fraction mapping reveals the non-uniform and high sp2 concentration existence at the interface of fiber/pyrolytic carbon. This result proves the cracking start at this region and extends to whole specimen.

III–V semiconductor GaP nanobelts were synthesized with a Fe2O3 catalyst on Si substrates by thermal evaporation at high temperatures. These nanobelts, typically, have a width from 50 to 600 nm and a length of up to several hundred micrometers. Their thickness varies from 10 to 40 nm. A vacancy ordering structure was observed near the edge of the GaP nanobelts. The vacancy ordering structure was analyzed using high-resolution transmission electron microscopy, electron diffraction patterns, and computer simulation. The unit cell of the vacancy ordering structure in the GaP belt is orthorhombic with lattice parameters a=3.767 A, b=6.525 A, c=18.456 A, and α=β=γ=90°. In the [111] projection, the structure is a R3x3 120° superstructure, while in the [211] projection, it exhibits a superstructure in both the (113) and (131) planes. This defective structure can also be visualized as a long period structure with a superstructure in the (111) stacking plane.

Direct methods in real and reciprocal space are developed for structural reversion. The direct method in real space involves the use of a novel method to retrieve the phase in the image plane using transport of intensity equation/maximum entropy method (TIE/MEM) and exit wave reconstruction by self-consistent propagation. Since the exit wave is restored from the complex signal in the image planes, no image model between the exit wave and image is assumed. The structural information in the reconstructed exit wave is then further extended by a "complex" maximum entropy method as a direct method in reciprocal space to extrapolate the phase to higher frequencies.

Different optimal operating conditions for a C 3 -corrected transmission electron microscope were compared for both conventional field emission sources and for the next generation of monochromated instruments. In particular, the contrast transfer functions and corresponding wave aberration functions for two previously proposed optimal conditions in which C 3 is adjusted to compensate, respectively, C 5 or C c are critically compared. The results indicate that in the presence of a small positive C 5 the former provides flat transfer to the information limit whereas the latter shows oscillatory transfer at high spatial frequencies, which is more pronounced for the monochromated instrument. The effects of this behaviour were further investigated through multislice simulations of Si [110] and diamond [110] under the C 5 -limited condition. These confirm that for the former structure with an interatomic separation of 0.14 nm this aberration has little influence, but that for the latter with a sub-0.1 nm interatomic separation its presence leads to a restricted defocus range over which the structure is faithfully resolved.

x4282 NiMn/NiFe/Co/Cu/Co/NiFe/seed layer and NiFe/CoFe/Cu/CoFe/Ru/CoFe/NiFe/NiMn/seed layer structures have been investigated using high resolution transmission electron microscopy (HRTEM) coupled with nanobeam energy dispersive X-ray (EDX) and electron energy loss spectroscopy (EELS). An accumulated sum technique was applied to analyse the lattice spacing variation across the ultra-thin film from HRTEM micrographs. A Wiener filter was used to remove the electron beam broadening effect from nanobeam EDX data to improve the spatial resolution of composition profiles. A combination of these two techniques (lattice variation measurement and the deconvolution of nanobeam EDX) allows any interdiffusion effects between the ultra-thin films in the spin-valve devices to be revealed. The compositional analysis shows that diffusion of Mn and Ni into the Cu/Co bilayer is only observed in the Co/Cu/Co sample. This result indicates that the Ru layer in the CoFe/Cu/CoFe sample might not only act as a spacer of the synthetic antiferromagnet but also behaves as a good diffusion barrier for Ni and Mn elements in the spin valve structure. The diffusion coefficients of constituent elements are simply determined by using the Matano–Boltzmann method from the deconvoluted compositional profiles. Diffusion of Cu in Co and Ni in Co is primarily by the grain boundary mechanism. In the CoFe/Cu/CoFe/Ru/CoFe sample, diffusivity of Cu and Ni is smaller than that in the Co/Cu/Co sample.

A convenient thermal CVD route to core−shell GaP@GaN and GaN@GaP nanowires is developed. The structural analyses indicate that the nanowires exhibit a two-layer and wirelike structure. High-resolution transmission electron microscopy (HRTEM) images reveal misfit dislocation loops at the interface of the nanowires. Unusual temperature dependences of the photoluminescence (PL) intensity of GaP@GaN nanowires are observed, and they are interpreted by the piezoelectric effect induced from lattice mismatch between two semiconductor layers. In the Raman spectra of GaN@GaP nanowires, an unexpected peak at 386 cm-1 is found and assigned to a surface phonon mode.

Background: Vasculogenic mimicry (VM) describes the functional plasticity of aggressive tumor cells to form newly recognized microcirculation, lined by tumor cells rather than endothelial cells, in solid tumors. The presence of VM in glioma is significantly associated with high tumor grade and poor prognosis. However, whether VM is a regular feature or only a temporary phenomenon during glioma growth is unknown. This study was designed to observe VM during the growth of subcutaneous and orthotopic xenograft glioma in Balb/c nude mice. Methods: The human glioblastoma cell line (U87) was used as xenografts in Balb/c nude mice models. The xenografts were obtained at different stages of tumor growth, and evaluated for VM and endothelium-dependent vessels by dual staining for endothelial marker CD34 and periodic acid-Schiff (PAS). Results: It was found that the PAS-positive patterns which were identified as VM were persistent during tumor growth of both subcutaneous and orthotropic xenografts. Further analysis showed that the microvessel density (MVD) of endothelium-dependent vessels was positively correlated with the tumor size of subcutaneous xenograft (r = 0.406, P = 0.009), while no significant correlation was found between VM density (VMD) and the tumor size (r = 0.107, P = 0.512). Furthermore, VMD was negatively correlated with MVD (r = −0.404, P = 0.010). Conclusion: The study results revealed that both VM and endothelium-dependent vessels coexist persistently during glioblastoma xenograft growth, indicating that VM may complement microcirculation in gliomas.

Artemisinin, a powerful antimalarial medicine, is extracted from the Chinese herb, Artemisia annua L., and has the ability to inhibit the proliferation of cancer cells. Dihydroartemisinin (DHA), the major active metabolite of artemisinin, is able to inhibit the growth of a variety of types of human cancer. However, the effect of DHA on human glioma cells remains unclear. The aim of the present study was to investigate the effect of DHA on the proliferation of glioma cells, and whether DHA was able to enhance temozolomide (TMZ) sensitivity in vitro and in vivo. In total, 10 human glioma cell lines were used to analyze the growth inhibition ability of DHA by MTT assay. The typical autophagic vacuoles were monitored by the application of the autofluorescent agent, monodansylcadaverine. Western blotting was used to detect markers of apoptosis and autophagy, namely Caspase-3, Beclin-1 and LC3-B. The combination efficiency of DHA and TMZ was assessed in vitro and in vivo. The half maximal inhibitory concentration (IC50) of DHA differed among the ten human glioma cell lines. The number of autophagic vacuoles was higher in DHA-treated SKMG-4 cells; this was highest of all cell lines analyzed. The expression of autophagy molecular markers, Beclin-1 and LC3-B, was increased following DHA treatment, while no significant alteration was detected in the expression of apoptotic marker Caspase-3. When combined with DHA, the IC50 of TMZ decreased significantly in the four glioma cell lines analyzed. Furthermore, DHA enhanced the tumor inhibition ability of TMZ in tumor-burdened mice. The results of the present study demonstrated that DHA inhibited the proliferation of glioma cells and enhanced the tumor inhibition efficacy of TMZ in vitro and in vivo through the induction of autophagy.

Recent advancements in aberration-corrected electron microscopy allow for an evaluation of unexpectedly large atom displacements beyond a resolution limit of similar to 0.5 angstrom, which are found to be dose-rate dependent in high resolution images. In this paper we outline a consistent description of the electron scattering process, which explains these unexpected phenomena. Our approach links thermal diffuse scattering to electron beam-induced object excitation and relaxation processes, which strongly contribute to the image formation process. The effect can provide an explanation for the well-known contrast mismatch ("Stobbs factor") between image calculations and experiments. (C) 2014 Elsevier Ltd. All rights reserved.

Transmission electron microscopy has been used to characterize Al segregation in Al 0.1 Ga 0.9 N and Al 0.3 Ga 0.7 N alloys grown by metal organic chemical vapor deposition on 6H-SiC. It has been found that an interlayer of AlGaN alloy with much higher Al content was formed at first, followed by normal growth of nominal composition of AlGaN alloy. In Al 0.1 Ga 0.9 N and Al 0.3 Ga 0.7 N films, dislocation lines were also found to have more Al segregated than those regions free of dislocations in the matrix. Furthermore, it shows that more Al atoms segregate to an edge dislocation than to a screw one.

A generalized maximum entropy method coupled with Gerchberg-Saxton algorithm has been developed to extend the resolution from high-resolution TEM image(s) for weak objects. The Gerchberg-Saxton algorithm restores spatial resolution by operating real space and reciprocal space projections cyclically. In our methodology, a generalized maximum entropy method (Kullback-Leibler cross entropy) dealing with weak objects is used as a real space (P1) projection. After P1 projection, not only are the phases within the input spatial frequencies improved, but also the phases in the next higher frequencies are extrapolated. An example of semi-blind deconvolution (P1 project only) to improve the resolution in SiC twin boundary is shown. The nature of the bonding in this twin boundary is Si-C but it was rotated 180 degrees along the boundary normal. The optimum solution from P1 projection can be further improved by a P2 projection. The square roots of diffraction intensities from a diffraction pattern are then substituted to complete a cycle operation of the Gerchberg-Saxton algorithm. Application examples of Gerchberg-Saxton algorithm to solve the atomic structure of defects (2 x 1 interfacial reconstruction and dislocation) in NiSi2/Si interfaces will be shown also.

Interfacial reactions of Cu/TaN x /Si and silicon nitride/Cu/TaN x /Si multilayers after thermal treatment at 500 and 700°C under an ambient with residual oxygen were investigated using an energy-filtered TEM (EFTEM). The Cu and TaN x films were deposited onto the Si (0 0 1) wafer by ionized metal plasma (IMP) technique. An interlayer of TaO x N y was observed between Cu and TaN x diffusion barrier in the Cu/TaN x /Si sample after 500°C annealing. It is evident that oxygen diffused through the Cu grain boundaries and promotes the oxidation of the Ta nitride barrier layer to form the TaO x N y . It is also found that the as-deposited TaN x ( x ∼0.5) film with nano-crystalline microstructure would transform into Ta 2 N structure with large grain character after 500°C heat treatment. After 700°C annealing, not only the TaN x barrier layer transformed into Ta 2 N but the silicidation of Cu to Cu 3 Si and TaN x to Ta 5 Si 3 occurred. However, no TaO x N y interlayer was observed. This may result from the preferable oxidation of Cu 3 Si that may suppress the oxidation of TaN x . Nevertheless, in the silicon nitride capped (silicon nitride/Cu/TaN x /Si) case, there was no TaO x N y interlayer observed in the 500°C annealed specimen. And the interfacial reaction in the silicon nitride/Cu/TaN x /Si annealed specimen at 700°C also showed much less severe extent than the sample without capping. Experiments show that the oxygen in the ambient enhances the oxidation at 500°C and silicidation at 700°C.

A mirror-glide symmetric structure is observed at the Σ=9 [0 1 1 ]/(1 2 2) symmetric tilt grain boundary in Cu. No mirror symmetric unit is found which is consistent with the fact that the mirror symmetric unit is relatively higher energy in low stacking fault energy, or higher bulk modulus, fcc metals. The boundary width is estimated to be about 0.1241 nm which is about twice of {2 2 4} lattice spacing.

Interfacial microstructures of TiNi thin films rf sputtered on to Si(100) and post-annealed at 400–700°C for 30mins have been investigated using analytical and high-resolution transmission electron microscopy. For annealing temperatures below 600°C, a very thin amorphous (Si, O)-rich layer is observed at the interface. Ni atoms are the primary diffusing species and NiSi2 forms triangularly and epitaxially towards the Si substrate. TiNi films initially crystallize after 30 min at 500°C. Si and Ti atoms begin to migrate in specimens annealed at 600°C for 30min. At this temperature, a near-Ti4Ni4Si7 phase in triangular NiSi2 and a near-TiNiSi phase in the TiNi film are simultaneously nucleated and grown at the interface. For the specimens annealed at 700°C for 30 min, two layers of Ti4Ni4Si7 and TiNiSi form at the interface with the sequence TiNi/TiNiSi/Ti4Ni4Si7/Si. Triangular NiSi2 islands are now embedded in the Ti4Ni4Si7 layer. A mechanism of interfacial microstructure evolution is proposed to e...

A thin Ti53Cu47 amorphous ribbon was prepared by rapid quenching from the melt. The crystallization behavior was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The DSC results indicated that the activation energy for crystallization was 170 or 150 kJ/mole (1.76 or 1.55 eV/atom) based on the Kissinger or Arrhenius plot, respectively, which is close to that of chemical diffusion in the TiCu alloy: 166 kJ/mol (1.72 eV/atom). The Johnson-Mehl-Avrami (JMA) plot exhibited a linearity, with an exponent of n=2.0 ±0.2. The XRD patterns revealed the transformation to the equilibrium γ-TiCu phase. However, broad peaks due to nanocrystalline grains were not observed. From the TEM analysis, there was a metastable phase with an fcc structure based on the Cu structure pre-existing in the as-quenched ribbon. Only a few TiCu particles in the nanoscale dimension were observed to precipitate from the amorphous matrix upon both continuous and isothermal heatings. A theoretical calculation demonstrates that amorphous Ti53Cu47 has a very low nucleation frequency and thus, a low tendency to form nanocrystals.

This work examines the thermal stability of Ta barrier layer for Cu metallization with the effect of oxygen. The Cu/Ta/SiO 2 /Si films were annealed at temperatures ranging from 400 to 600°C under various vacuum conditions. Transmission electron microscopy has been performed to characterize the microstructure of the films after annealing. The results show that an amorphous interlayer of oxide between Cu and Ta can be formed at 400°C in a vacuum of 10 −2 mbar. X-Ray energy dispersive spectroscopy and electron energy loss spectroscopy confirm that this interlayer is tantalum oxide. This interlayer transformed into a crystalline phase of Ta–Cu oxide at 600°C. In addition, formation of tantalum oxide interlayer is more thermodynamically favorable than that of copper oxide layer at the Cu/Ta interface. Growth of the amorphous interlayer is atmosphere-dependent, as evidenced by the thickness of tantalum oxide being decreased with better vacuum or argon gas. This observation suggests that the oxidation source may arise from the annealing atmosphere rather than from interior SiO 2 . Furthermore, it has been observed that oxygen diffuses along grain boundaries in copper films to cause tantalum oxidation.

Interfacial reactions of Cu/Ta/Si multilayers after thermal treatment were investigated using transmission electron microscopy. The Cu and Ta films were deposited onto Si wafer by ionized metal plasma technique. The samples were then annealed at 400, 500, 550 and 600°C in purified Ar atmosphere for 30 min. The effect of oxygen in the atmosphere on the thermal stability is studied. An interlayer of Ta oxide was observed between Cu and Ta after annealing at 400, 500 and 550°C. It is evident that oxygen as residual gas from furnace ambient can diffuse through Cu grain boundaries to form the Ta oxide layer. After annealing at 600°C, Si reacted with Ta to form TaSi 2 at the interface of Ta and Si, in the meantime Cu 3 Si with surrounding SiO 2 formed in the Si substrate. The thermal stability of the Cu/Ta/Si samples was also examined in a two-step annealing treatment of 400°C for 30 min, followed by 600°C for 30 min. Even though interlayers of crystalline Ta–Cu oxide and Ta silicide were formed, Cu silicides were not observed. Formation of TaO x interlayer at the first stage of 400°C annealing may inhibit Cu diffusion into the Si substrate in the second stage of the 600°C annealing process.

The purpose of this study is to develop a model to describe the effects of the grain boundary misorientation on the radiation-induced solute segregation (RIS) in 304 stainless steels. A simple rate equation model with modified boundary conditions, which included the fluxes of defects diffusing along the grain boundaries to the grain boundary dislocations, was developed for RIS at boundaries with different Σ values. The results of the model calculations were compared to the experimental results previously reported by us. It was found that the model could clearly predict the same trends that the Cr depletion levels at special boundaries in irradiated 304 stainless steels were increasing with Σ. The model calculations also showed that the widths of the segregation cusps was decreasing with increasing Σ.

Heteroepitaxial diamond films were successfully nucleated and deposited on 1-inch diameter Si(001) substrates by microwave plasma-enhanced chemical vapor deposition (MPECVD). The precursor gases for the synthesis were methane and hydrogen. Before the application of a negative d.c. bias to the substrate, an in-situ carburization pre-treatment on the silicon was found to be an indispensable step towards the heteroepitaxial diamond on the silicon. Morphologies of the films were characterized by scanning electron microscopy (SEM). Interface observations based on the cross-sectional HRTEM directly reveal the heteroepitaxial diamond nucleation phenomena in detail. No interlayers of silicon carbide and/or amorphous carbon phases were observed. Tilt and azimuthal misorientation angles between the heteroepitaxial diamond crystals and the substrate were determined by combining the Ewald sphere construction in the reciprocal lattice space and the selected area diffraction (SAD) patterns taken across the interface.

Deposition of heteroepitaxial diamond on substrates of 6H-SiC single crystal by a d.c. voltage biased-enhanced microwave plasma chemical vapor deposition method has been attempted. Various concentrations of methane (CH 4 ) up to 10% in hydrogen (H 2 ) was used to evaluate its effect on epitaxy. Characterization of cross-sectional transmission electron microscopy with electron energy loss spectroscopy shows that an interlayer can form between diamond 6H-SiC, depending on the CH 4 concentration. With low CH 4 concentration, diamond was directly nucleated on 6H-SiC with an orientation relationship of diamond {111}//6H-SiC {0001} and diamond 〈110〉//6H-SiC 〈1120〉.

Three types of linear defects are observed by high-resolution electron microscopy along the InAs/GaAs(001) interface formed by molecular beam epitaxy deposition of InAs (300 nm) on a GaAs substrate: classical 90° and 60° misfit dislocations and an unusual type of linear defect that is a (110) nanofacet extended over ∼1 nm and bordered by a 60° dislocation (1/2)[101]. Extensive numerical simulations show that the total Burgers vector content of the defect, which includes the contributions of the 60° dislocation and that of a dislocation distribution along the nanofacet, is very close to (1/12)[605] or (1/12)[065], according to the sense of the screw component. A comparison between the experimental and calculated elastic displacement fields has been undertaken from image contrast simulations and the theory of dislocation distribution.

The effect of heat treatment temperature on the microstructure and specific contact resistance of oxidized Ni(5 nm)/Au(5 nm) contacts to p-type GaN was investigated. The minimum specific contact resistance (ρc) obtained was 4 × 10—6 Ω cm2 after heat treating at 500 °C in air for 10 min. The cross-sectional microstructure of heat treated Ni/Au films on p-type GaN was examined with transmission electron microscope (TEM) in conjunction with compositional analyses. The high value of ρc for samples heat treated at lower temperatures (

A contact has been developed to achieve a low specific contact resistance to p-type GaN. The contact consisted of a bi-layer Ni/Au film deposited on p-type GaN followed by heat treatment in air to transform the metallic Ni into NiO along with an amorphous Ni–Ga–O phase and large Au grains. A specific contact resistance as low as 4.0×10−6 Ω cm2 was obtained at 500 °C. This low value was obtained by the optimization of Ni/Au film thickness and heat treatment temperatures. Below about 400 °C, Ni was not completely oxidized. On the other hand, at temperatures higher than about 600 °C, the specific contact resistance increased because the NiO detached from p-GaN and the amount of amorphous Ni–Ga–O phase formed was more than that of the sample annealed at 500 °C. The mechanism of obtaining low-resistance ohmic contacts for the oxidized Ni/Au films was explained with a model using energy band diagrams of the Au/p-NiO/p-GaN structure.

The structure of the InAs/GaAs(001) epitaxial heterointerface is observed by high resolution electron microscopy (HREM) along [110] when there is a slight long range angular misorientation between the two crystals around the common observation direction. The lattice misfit and the local misorientation (η = 6.9%, Δθ = 1.5°) are simultaneously accommodated via a non planar and non pseudoperiodic distribution of defects involving usual 90° and 60° dislocation cores and yet unreported nanoledges with exotic Burgers vector contents. One of these nanoledges is five (001) planes high and has a total Burgers vector content equal to (1/6)[33-1]. Its local elastic field has been analysed in terms of ribbon-like Somigliana dislocations. It depends on η, Δθ and its nanoledge height. Comparisons between the experimental and calculated tunnel positions between atom columns are given to appreciate the validity of the model.

The mechanical properties of the high-strength 7XXX series aluminum alloys can be improved through microstructural modifications in addition to alloy compositional changes. Among microstructural features, the effect of texture on mechanical properties was least well understood. By plastic deformation of a metal specimen, the crystalline lattice rotates toward one or more stable (preferred) orientations, thus establishing a deformation texture. Since the rolling process tends to increase the tendency of a sharp texture and the localization of plastic deformation, it is interesting to study in detail the influence of texture on the deformation behavior of a rolled metal. The studies in the past investigated mainly the influences of microstructural features on the material properties under tensile stress. Since compression is more closely related to most metal working processes, the objective of this study is to investigate the formation of shear band in compression and the effect on texture on the shear band formation of a 7050-T7451 aluminum alloy.

A (111)NiSi 2 //(115)Si heterotwin interface has been observed by high resolution electron microscopy (HREM) along the common direction [110]NiSi 2 //[110]Si to identify the long period atomic structural units (ASU's). Coexistence of two different structural domains has been found with ASU's corresponding to two different cycles of five-, six-, and seven-atom rings. A dislocation/ledge (DL) has been particularly studied because its separates these two unusual cycles of ASU's. The elastic displacement field u of the atom columns around the DL has been calculated using both crystallographic and anisotropic elasticity properties of the crystals, assuming a two-dimensional u field. From a comparison between the positions of the atom columns as derived from elasticity calculations and as deduced from the HREM image, it is concluded that the DL is a mixed dislocation with the Burgers vector (-1/4)[111]NiSi 2 + (1/2)[110]Si = (1/12)[515]Si, a result also in agreement with the imperceptible ledge height associated with the DL core. Such a Burgers vector underlines the role of the Si matrix dislocations for producing such structural domains.

Diamond-like carbon (DLC) coatings were successfully produced on the silicon wafer by a microwave plasma enhanced chemical vapor deposition (MPECVD) with the precursor gases of methane, hydrogen and argon. High resolution transmission electron microscopy (HRTEM) was applied to analyze the nano-particles in the coating. Both diamond and silicon carbide (SiC) nano-clusters of sizes ranging from 2 to 5 nm were observed in the DLC films. The dispersion of nano-clusters of diamond and SiC improves the film quality in terms of crystallinity and hardness of the DLC coating significantly.

A thin Ti73Fe27 ribbon was prepared by rapid quenching from the melt. The as-quenched ribbon was in a metastable condition with a small amount of nanoparticles of TiFe, of a size of 138±31 nm, embedded in the β-Ti matrix. The β-Ti matrix was supersaturated with Fe, and the fraction of the matrix was higher than that in the equilibrium state. High-resolution imaging of the interface of the TiFe/β-Ti showed that a periodic array of dislocations were present in the interface to accommodate the lattice mismatch. The spacing between the dislocations in the as-quenched specimen was 5.0±0.5 nm. When the ribbon was heated to 700 °C, growth of the TiFe nanoparticles to a size of 228±37 nm took place in the β-Ti matrix. The amount of β-Ti was reduced, as well as the Fe content in β-Ti. The interface between the TiFe and β-Ti remained semicoherent, except that the spacing between the interfacial dislocations was reduced to 3.5±0.6 nm. The persistence of the semicoherent interface was ascribed to the same crystal structure and close lattice parameters shared by TiFe and β-Ti. The growth kinetics of the TiFe nanoparticles during heating was examined based on the modified theory of isothermal heating. It can be considered to be controlled by the diffusion of Fe atoms in the β-Ti matrix to the TiFe phase. Prolonged heating of the ribbon below the eutectoid temperature led to partial transformation of β-Ti to α-Ti.

Compositional evolution of 18R martensite and α-Mn particles in aging a duplex Fe-Mn-Al-C alloy was studied by a Field Emission Gun Transmission Electron Microscope (FEG TEM) JOEL JEM-2010F equipped with EDS and Gatan imaging filter. A model was proposed to explain the compositional and structural evolution of the 18R martensite during aging treatment.

A single 210-nm Teflon nanoparticle (sTNP) was attached to the vertex of a silicon nitride (Si3N4) atomic force microscope tip and charged via contact electrification. The charged sTNP can then be considered a point charge and used to measure the electrostatic field adjacent to a parallel plate condenser using 30-nm gold/20-nm titanium as electrodes. This technique can provide a measurement resolution of 250/100 nm along the X- and Z-axes, and the minimum electrostatic force can be measured within 50 pN. PACS 07.79.Lh, 81.16.-c, 84.37. + q

OBJECTIVES: Primary sarcomas of the mediastinum are relatively rare. This article reviews the surgical outcomes of 21 cases diagnosed with localized mediastinal sarcomas receiving multidisciplinary treatment modalities in Sichuan province, China, from January 1996 to January 2011. METHODS: Twenty-one cases of histologically diagnosed primary mediastinal sarcoma undergoing surgical treatment were reviewed retrospectively. Disease-free survival (DFS) and overall survival (OS) were statistically analysed. All the patients presented with localized tumours consisting of 5 females and 16 males with a median age of 41.0 years (range: 9.0–68.0 years). Among all cases, 17 (81.0%) had an Eastern Cooperative Oncology Group performance status score of ≤1 at diagnosis. Eight (38.1%) underwent macroscopically complete resection (R0–R1) and 13 (61.9%) had incomplete resection (R2). Ten (47.6%) received postoperative radiotherapy and 7 (33.3%) postoperative chemotherapy. RESULTS: The median DFS was 17 months (range: 0.4–79.8 months) and the median OS was 27.2 months (range: 0.4–79.8 months). Patients receiving complete resection showed significantly improved DFS (P= 0.031) and OS (P= 0.035) compared with those with incomplete resection. Neither postoperative radiotherapy nor chemotherapy significantly improved DFS (P= 0.770, P= 0.756) or OS (P= 0.905, P= 0.738). However, 7 patients (R2) and 2 (R0–R1 and grade 3) had improved local control with a local recurrence-free survival of 28.9 months (range: 7.6–73.2 months). CONCLUSIONS: Complete resection should be preferentially attempted compared with incomplete resection and postoperative radiotherapy might yield good local control.

Diamond was deposited on Si(100) substrates by microwave plasma assisted chemical vapor deposition in three steps: carburization, biasing and growth. High-resolution transmission electron microscopy (TEM) in cross-sectional view has been used to observe the evolution of microstructures around the interfacial region between diamond and Si in each processing step. The chemistry near the interface was characterized with elemental mapping using an energy-filtered TEM imaging technique. In the carburization stage, an amorphous SiC interlayer 1.5 nm thick was formed between an amorphous carbon layer and Si. In the following biasing stage, β-SiC can form in epitaxial orientation with Si. In the growth stage, diamond grains aligned in a strongly textured condition developed, while the initially grown diamond had polycrystalline characteristics. Processing conditions for epitaxial diamond deposition on Si substrates are briefly discussed.

Martensitic transformation in a BCC matrix in duplex Fe-Mn-Al-C alloys had been studied by several researchers. However, morphology and structure of martensite variants in Fe-Mn-Al-C alloy have not been studied intensively yet. Especially, application of high resolution transmission electron microscopy (HRTEM) in this area of study is rare so far. In this paper, the authors present a HREM study of group variants of martensite in an Fe-Mn-Al-C alloy. The HRTEM could reveal local structures between variants in nanometer scale which may not be detectable by conventional TEM technique.

Heteroepitaxial diamond has been successfully deposited on a Si(110) substrate by the microwave plasma chemical vapor deposition method. The pretreatment consisted of carburization and bias-enhanced nucleation steps. Cross-sectional transmission electron microscopy reveals that diamond can be in the cube-on-cube epitaxial relationship with the Si substrate. Various orientation relationships between diamond and Si substrates have also been observed, depending on the location where the plasma applied. Near the center of the plasma, twins were rarely observed in cube-on-cube epitaxial regions. Away from the center of the plasma ball, Σ3 twins are seen first, and then additional Σ9 and Σ27 twins occur near the edge of the plasma. In general, defect density in the epitaxial films is less than that observed in polycrystalline ones. No interlayer could be observed between diamond and silicon. In addition, 2H-type hexagonal diamond has also been found, and is in epitaxy with the Si substrate.