Home About us Contact
|
Home About us Contact | ||
|
|
||
Cross-sectional Transmission Electron Microscopy (cross-sectional + transmission_electron_microscopy)
Selected AbstractsDetermination of mean free path for energy loss and surface oxide film thickness using convergent beam electron diffraction and thickness mapping: a case study using Si and P91 steelJOURNAL OF MICROSCOPY, Issue 2 2006D. R. G. MITCHELL Summary Determining transmission electron microscope specimen thickness is an essential prerequisite for carrying out quantitative microscopy. The convergent beam electron diffraction method is highly accurate but provides information only on the small region being probed and is only applicable to crystalline phases. Thickness mapping with an energy filter is rapid, maps an entire field of view and can be applied to both crystalline and amorphous phases. However, the thickness map is defined in terms of the mean free path for energy loss (,), which must be known in order to determine the thickness. Convergent beam electron diffraction and thickness mapping methods were used to determine , for two materials, Si and P91 steel. These represent best- and worst-case scenario materials, respectively, for this type of investigation, owing to their radically different microstructures. The effects of collection angle and the importance of dynamical diffraction contrast are also examined. By minimizing diffraction contrast effects in thickness maps, reasonably accurate (±15%) values of , were obtained for P91 and accuracies of ±5% were obtained for Si. The correlation between the convergent beam electron diffraction-derived thickness and the log intensity ratios from thickness maps also permits estimation of the thickness of amorphous layers on the upper and lower surfaces of transmission electron microscope specimens. These estimates were evaluated for both Si and P91 using cross-sectional transmission electron microscopy and were found to be quite accurate. [source] Formation of nanovoids/microcracks in high dose hydrogen implanted AlNPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2008R. Singh Abstract Aluminium nitride (AlN) epitaxial layers grown on sapphire were implanted with 100 keV hydrogen, H2+ ions with doses in the range of 5 × 1016 cm,2 to 2.5 × 1017 cm,2 and subsequently annealed at temperatures up to 800 °C in order to observe the formation of surface blisters. The implantation-induced damage in AlN was analyzed by cross-sectional transmission electron microscopy, which revealed a band of defects extending from 330,550 nm from the surface of AlN. Higher magnification TEM images showed the formation of nanovoids that are distributed in the damage band. Upon annealing these nanovoids agglomerate leading to the formation of microcracks. Due to the overpressure of hydrogen trapped in the microcracks, surface blisters are eventually formed in the hydrogen implanted AlN. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Annealing effect on an exchange-biasing Co/IrMn systemPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2007Yuan-Tsung Chen Abstract The top-configuration Co(y)/IrMn(90 Å) exchange-biasing phenomenon has been studied by sputtering method with two conditions: (a) the substrate temperature (Ts) was kept at room temperature (RT) only, and (b) Ts = RT with an in-plane field (h) = 500 Oe deposition and postdeposition annealing in the field at TA = 250 °C for 1 h, with the samples field cooled to RT. High resolution electron cross-sectional transmission electron microscopy (HR X-TEM) reveals that the IrMn (111) texturing plays a main role to exchange-biasing field (Hex) and interfacial energy (Jk). The Hex versus y result shows that Hex increases when y decreases in case (b). Since Jk = HexMsy, where Ms is Co magnetization, it is easy to derive Hex = Jk/(Msy). Therefore, if Hex is inversely proportional to y, with Jk/Ms constant, we find Hexy = constant. In case (a), Hex is very small in general, while in case (b), Hex is of the order of 60-180 Oe. Moreover, the y dependence of Jk is similar to that of Ms for each curve. Finally, the Hc is inversely proportional to y because of the surface pinning effects from the Ta/Co and Co/IrMn interfaces. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Atomic Layer Deposition, Characterization, and Dielectric Properties of HfO2/SiO2 Nanolaminates and Comparisons with Their Homogeneous Mixtures,CHEMICAL VAPOR DEPOSITION, Issue 2-3 2006L. Zhong Abstract Nanolaminates of HfO2 and SiO2 were prepared using atomic layer deposition (ALD) methods. Successive exposure of substrates maintained at 120 or 160,°C to nitrogen flows containing Hf(NO3)4 and (tBuO)3SiOH led to typical bilayer spacings of 2.1,nm, with the majority of each bilayer being SiO2. The density of the SiO2 layers (measured using X-ray reflectometry (XRR)) was slightly higher than expected for amorphous silica, suggesting that as much as 10,% HfO2 was incorporated into the silica layers. Based on cross-sectional transmission electron microscopy (TEM) and XRR, oxidation of the silicon substrate was observed during its first exposure to Hf(NO3)4, leading to a SiO2 interfacial layer and the first HfO2 layer. Combining the ALD of Hf(NO3)4/(tBuO)3SiOH with ALD cycles involving Hf(NO3)4 and H2O allowed the systematic variation of the HfO2 thickness within the nanolaminate structure. This provided an approach towards controlling the dielectric constant of the films. The dielectric constant was modeled by treating the nanolaminate as a stack of capacitors wired in series. The nanolaminate structure inhibited the crystallization of the HfO2 in post-deposition annealing treatments. As the HfO2 thickness decreased, the preference for the tetragonal HfO2 phase increased. [source] | ||||||||||