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III-Nitride Materials and Characterization
Published in Wengang (Wayne) Bi, Hao-chung (Henry) Kuo, Pei-Cheng Ku, Bo Shen, Handbook of GaN Semiconductor Materials and Devices, 2017
Bo Shen, Ning Tang, XinQiang Wang, ZhiZhong Chen, FuJun Xu, XueLin Yang, TongJun Yu, JieJun Wu, ZhiXin Qin, WeiYing Wang, YuXia Feng, WeiKun Ge
Selected area diffraction (SAD) is a strong tool to analyze the crystalline structure in a micro–area by adjusting the field slit at the first imaging plane. The back focal plane is placed on the imaging apparatus, and then a diffraction pattern can be generated. For thin crystalline samples, this produces an image that consists of a pattern of dots in the case of a single crystal or a series of rings in the case of a polycrystalline or amorphous solid material. Figure 1.31 is a typical SAD pattern from the interface region of a cross-sectional TEM specimen with the incident electron beam parallel to the [11-20]GaN direction [105]. This Figure is a superposition of the [1-120]GaN and [1-100]Al2O3 zone axes diffraction patterns of the GaN film and sapphire substrate, respectively. The composite diffraction pattern of Figure 1.31 indicates that the GaN film is single crystalline with an epitaxial orientation relationship (OR) with respect to the sapphire substrate given by (0001)GaN//(0001)Al2O3, or (11-20)GaN//(1-100)Al2O3.
Asbestos fiber length and width comparison between manual and semi-automated measurements
Published in Journal of Occupational and Environmental Hygiene, 2022
Taekhee Lee, Teresa Barone, Elaine Rubinstein, Steven Mischler
The characterization of asbestos requires information on fiber morphology and minerology (Skinner et al. 1988). This information can be obtained by transmission electron microscopy (TEM) through imaging and selected area diffraction (Baron 2016). However, TEM analysis is often cost-prohibitive due to instrument acquisition, maintenance, and training expenses. Lower cost methods, such as phase-contrast microscopy (PCM), lack mineral identification capabilities but suggest the presence of asbestos through the analysis of fiber length and width (Baron 2016). Fiber length is an important metric because long fibers can impair macrophage function and reduce lung clearance (Blake et al. 1997). Width is also influential because (together with length) it affects location of deposition in the respiratory system and the nature of associated respiratory diseases (i.e., mesothelioma, asbestosis, and lung cancer) (Lippmann 1988). When linking fiber characteristics to adverse health effects, information on both length and width is critical.
Solid–state diffusion–controlled growth of the phases in the Au–Sn system
Published in Philosophical Magazine, 2018
Varun A. Baheti, Sanjay Kashyap, Praveen Kumar, Kamanio Chattopadhyay, Aloke Paul
Pure Au (99.95 wt.%) and Sn (99.99 wt.%) were used as starting materials. The method for preparation of the bulk diffusion couples is extensively discussed in Chapter 3, Volume 1 of Handbook of Solid State Diffusion [20] and therefore not described here. For the preparation of the electroplated diffusion couples, electroplating of Sn at a current density of 20 mA/cm2 [21] on Au substrate was conducted in an air-conditioned (AC) room maintained at 20 ± 5 °C. The thickness of the electroplated layers was in the range of 0.5–1 mm to ensure that the ends of the diffusion couples (i.e. end members) are unaffected after the completion of diffusion annealing. Experiments were conducted in the temperature range of 25 (RT) to 200 °C. RT experiments were conducted by keeping the diffusion couples in a vacuum desiccator. For conducting other experiments at higher temperatures, a calibrated (±5 °C) high vacuum oven (~10−4 Pa) was employed. Time dependent experiments were conducted at 200 °C for 4–81 h to examine the growth kinetics of various phases. The interdiffusion zone was examined using a field emission gun equipped scanning electron microscope (FE–SEM) and composition measurements were performed in an electron probe micro-analyzer (FE–EPMA). The samples for TEM (transmission electron microscope) analysis were prepared using dual column FIB (focused ion beam) technique. JEMS software was used for indexing the selected area diffraction patterns acquired from TEM operating at 300 kV.
Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contacts
Published in Cogent Engineering, 2018
M. A. Awaah, U. Obahiagbon, H. Mohammed, O. Akpa, I. Awaah, T. Isaac-Smith, N. Korivi, J. B. Posthill, K. Das
The thickness of the deposited CGS and metal films was measured using a surface contact profiler (KLA Tencor p-6) and deposition rates were determined. Rutherford back scattering was used for determining the composition of the CGS films. A 2-MeV He+ beam was employed for the Rutherford backscattering spectroscopy (RBS) analysis. Samples of 1 cm2 of deposited absorber material were mounted to a target using silver paint. The He+ ion beam was accelerated toward the samples using a tandem electrostatic accelerator. Samples were bombarded with the He+ beam. The yield as well as energy distribution of the backscattered He+ ions at a given angle were measured and recorded. Transmission electron microscopy (TEM) of a cross-sectional sample was performed to study the interface between the CGS film and the Si substrate, and the nature of the deposited films. The cross-sectional sample strips were prepared from the 1-cm2 samples which were cross-sectioned and glued back to back, dimpled and then ion-milled. Diffraction patterns and high magnification images of the sample cross-sections were obtained. This analysis was used to obtain morphologic, compositional and crystallographic information on deposited absorber samples. Bright and dark field images as well as high resolution micrographs and selected area electron diffraction patterns (selected area diffraction patterns [SADPs]) were obtained.