Nucleation of diamond by pure carbon ion bombardment - a transmission electron microscopy study

A cross-sectional high-resolution transmission electron microscopy (HRTEM) study of a film deposited by a 1 keV mass-selected carbon ion beam onto silicon held at 800 degrees C is presented. Initially, a graphitic film with its basal planes perpendicular to the substrate is evolving. The precipitation of nanodiamond crystallites in upper layers is confirmed by HRTEM, selected area electron diffraction, and electron energy loss spectroscopy. The nucleation of diamond on graphitic edges as predicted by Lambrecht [W. R. L. Lambrecht, C. H. Lee, B. Segall, J. C. Angus, Z. Li, and M. Sunkara, Nature, 364 607 (1993)] is experimentally confirmed. The results are discussed in terms of our recent subplantation-based diamond nucleation model. (c) 2005 American Institute of Physics.

Resolution deterioration in emission electron microscopy due to object roughness

In the present paper a general analytic expression has been obtained and confirmed by a computer simulation which links the surface roughness of an object under study in an emission electron microscope and it's resolution. A quantitative derivation was made for the model case when there is a step on the object surface. It was shown that the resolution is deteriorated asymmetrically relative to the step. The effect sets a practical limit to the ultimate lateral resolution obtainable in an emission electron microscope.

Investigation on the static recording characteristic of super-resolution near-field structure with antimony mask layer

Static recording characteristic of super-resolution near-field structure with antimony (Sb) is investigated in this paper. The recording marks are observed by a scanning electron microscopy (SEM), a high-resolution optical microscopy with a CCD camera and an atomic force microscopy (AFM). The super-resolution mechanism is also analyzed based on these static recording marks. Results show that the light reaching on recording layer is composed of two parts, one is the linear transmissive light (propagating field) and the other is the nonlinear evanescent light in the optical near field. The evanescent light may be greatly enhanced in the center of the spot because Sb will transit from a semiconductor to a metal when it is melted under the high laser power irradiation. This local melted area in the spot center may be like a metal tip in the optical near field that can collect and enhance the information that is far beyond the diffraction limit, which leads to the super-resolution recording and readout. (c) 2005 Elsevier Ltd. All rights reserved.

A transmission electron microscopy study of microstructural defects in proton implanted silicon

The microstructure of silicon on defect layer, a new type of silicon-on-insulator material using proton implantation and two-step annealing to obtain a high resistivity buried layer beneath the silicon surface, has been investigated by transmission electron microscopy. Implantation induced a heavily damaged region containing two types of extended defects involving hydrogen: {001} platelets and {111} platelets. During the first step annealing, gas bubbles and {111} precipitates formed. After the second step annealing, {111} precipitates disappeared, while the bubble microstructure still remained and a buried layer consisting of bubbles and dislocations between the bubbles was left. This study shows that the dislocations pinning the bubbles plays an important role in stabilizing the bubbles and in the formation of the defect insulating layer. (C) 1996 American Institute of Physics.

A HIGH-RESOLUTION SOLID-STATE NMR-STUDY OF THE MISCIBILITY, MORPHOLOGY, AND TOUGHENING MECHANISM OF POLYSTYRENE WITH POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE) BLENDS

An extended Goldman-Shen pulse sequence was used to observe indirectly the proton spin diffusion in the blends of polystyrene (PS) with poly(2,6-dimethyl-1,4-phenylene oxides) (PPO). The results indicate that the average distance between PS and PPO is less than 5 angstrom in the intimately mixed phase, but there are heterogeneous domains on a 100-angstrom scale. The data of spin relaxation of carbons, T1(C), for homopolymers and their blends suggest that there is a strong pi-pi electron conjugation interaction between the aromatic rings of PS and those of PPO, while the aromatic rings of PPO drive the aromatic rings of PS to move cooperatively. It is the cooperative motion that markedly improves the impact strength of PS.

High-Resolution Finite Compact Difference Schemes for Hyperbolic Conservation Laws

A finite compact (FC) difference scheme requiring only bi-diagonal matrix inversion is proposed by using the known high-resolution flux. Introducing TVD or ENO limiters in the numerical flux, several high-resolution FC-schemes of hyperbolic conservation law are developed, including the FC-TVD, third-order FC-ENO and fifth-order FC-ENO schemes. Boundary conditions formulated need only one unknown variable for third-order FC-ENO scheme and two unknown variables for fifth-order FC-ENO scheme. Numerical test results of the proposed FC-scheme were compared with traditional TVD, ENO and WENO schemes to demonstrate its high-order accuracy and high-resolution.

Transmission Electron Microscopy Characterization of Laser Welding Cast Ni-Based Superalloy K418 Turbo Disk And Alloy Steel 42Crmo Shaft

Microstructure characterization is important for controlling the quality of laser welding. In the present work, a detailed microstructure characterization by transmission electron microscopy was carried out on the laser welding cast Ni-based superalloy K418 turbo disk and alloy steel 42CrMo shaft and an unambiguous identification of phases in the weldment was accomplished. It was found that there are gamma-FeCrNiC austenite solid solution dendrites as the matrix, (Nb, Ti) C type MC carbides, fine and dispersed Ni-3 Al gamma' phase as well as Laves particles in the interdendritic region of the seam zone. A brief discussion was given for their existence based on both kinetic and thermodynamic principles. (c) 2007 Elsevier B.V. All rights reserved.

Fiber Bragg grating temperature sensor for multiplexed measurement with high resolution

A novel fiber Bragg grating temperature sensor is proposed and experimentally demonstrated with a long-period grating as a linear response edge filter to convert wavelength into intensity-encoded information for interrogation. The sensor is embedded into an aluminum substrate with a larger coefficient of thermal expansion to enhance its temperature sensitivity. A large dynamic range of 110 degreesC and a high resolution of 0.02 degreesC are obtained in the experiments. The technique can be used for multiplexed measurements with one broadband source and one long-period grating, and therefore is low Cost. (C) 2004 Society of PhotoOptical Instrumentation Engineers.

Femtosecond laser pulse irradiation of Sb-rich AgInSbTe films: Scanning electron microscopy and atomic force microscopy investigations

The single-layer and multilayer Sb-rich AgInSbTe films were irradiated by a single femtosecond laser pulse with the duration of 120 fs. The morphological feature resulting from the laser irradiation have been investigated by scanning electron microscopy and atom force microscopy. For the single-layer film, the center of the irradiated spot is a dark depression and the border is a bright protrusion; however, for the multilayer film, the center morphology changes from a depression to a protrusion as the energy increases. The crystallization threshold fluence of the single-layer and the multilayer films is 46.36 mJ/cm(2), 63.74 mJ/cm(2), respectively.

Structural role of fluoride in aluminophosphate sol-gel glasses: High-resolution double-resonance NMR studies

The local structure of Na-Al-P-O-F glasses, prepared by a novel sol-gel route, was extensively investigated by advanced solid-state NMR techniques. Al-21{F-19} rotational echo double resonance (REDOR) results indicate that the F incorporated into aluminophosphate glass is preferentially bonded to octahedral Al units and results in a significant increase in the concentration of six-coordinated aluminum. The extent of Al-F and Al-O-P connectivities are quantified consistently by analyzing Al-27{P-31} and Al-21{F-19} REDOR NMR data. Two distinct types of fluorine species were identified and characterized by various F-19{Al-27}, F-19{Na-23}, and F-19{P-31} double resonance experiments, which were able to support peak assignments to bridging (Al-F-Al, -140 ppm) and terminal (Al-F, -170 ppm) units. On the basis of the detailed quantitative dipole-dipole coupling information obtained, a comprehensive structural model for these glasses is presented, detailing the structural speciation as a function of composition.

离子束溅射法薄膜生长中结瘤微缺陷的生长机理

用离子束溅射法制备了锆单层薄膜．用设计新型夹具和预置种子方法，对薄膜中结瘤微缺陷的生长过程进行了研究．在高分辨率光学显微镜和扫描电子显微镜下观察发现，结瘤在其生长初期呈现出分形的特征．用分子动力学和薄膜生长的扩散限制聚集模型，薄膜中结瘤微缺陷成核时的分形现象得到了很好的解释．

Metabolic changes in rat prefrontal cortex and hippocampus induced by chronic morphine treatment studied ex vivo by high resolution H-1 NMR spectroscopy

Ex vivo H-1 NMR spectroscopy was used to measure changes in the concentrations of cerebral metabolites in the prefrontal cortex (PFC) and hippocampus of rats subjected to repeated morphine treatment known to cause tolerance/dependence. The results show th