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The History of Nuclear Medicine
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
The SPECT systems were further developed and characterized as more robust rotation gantries and dual detectors. Dedicated scintillation cameras for smaller organs, particularly in high-resolution cardiac imaging, were constructed based on the new cadmium zinc telluride (CZT) solid-state detector technology. Methods for attenuation and scattering correction in SPECT have evolved, enhancing the image quality and quantification and hence the diagnostic quality. At the end of the 1990s, the SPECT systems were combined with low-dose and few-slice CT mounted on the same rotation gantry to perform patient-specific attenuation correction through transmission measurements. Subsequently, SPECT and fully complete CT were combined into hybrid SPECT/CT systems. Hence, the simultaneous acquisition of functional information from the SPECT and anatomical information from the CT could be accomplished and, after image processing resulting in superimposed images, so-called image fusion. The further development of SPECT in recent years in addition to the significant progress in computing power has resulted in the introduction of the CZT solid-state detectors, replacing the PMT and special multi-pinhole collimator, which is used in SPECT/MRI brain-imaging systems.
Quantum Dots:
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials II, 2021
Kulvinder Singh, Shikha Sharma
Etching also plays a vital role in the fabrication of quantum dots. In the case of dry etching, the reactive gas molecules are introduced in the etching compartment, followed by applying the radio frequency of desired voltage to generate plasma which disintegrates the molecules (gas) to more responsive fragments. These highly energetic species collide on the surface and fabricate a reactive product to etch the patterned sample. If these energetic fragments are ions, the etching methodology is called reactive ion etching. Gallium arsenide/aluminum gallium arsenide quantum dots are reported to be synthesized by using reactive ion etching with the aid of boron trichloride and argon (Scherer et al. 1987). Zinc telluride quantum dots have been synthesized by the same reaction protocol using methane and hydrogen gas (Tsutsui et al. 1993).
Ceramics: Processing, Properties, and Applications
Published in Noureddine Ramdani, Polymer and Ceramic Composite Materials, 2019
Ceramics can have either a crystalline or amorphous structure. Crystalline ceramics can be divided into several groups according to their mono-crystal structures [3]. For example, when the anions (negatively-charged nonmetallic ions) and cations (positively-charged metallic ions) form two interpenetrating FCC lattices, a coordination number of 6 (six nearest neighbors) is obtained, this structure is similar to that of the rock salt structures, including NaCl, MgO, and LiF (Figure 2.1a). However, in the cesium chloride (CsCl) structure (Figure 2.1b), the coordination number for both anions and cations is 8, with eight anions located at the corners of a cube and a single cation residing at the cube center. In the ZnS crystal structure (Figure 2.1c), all corner and face centers are taken by sulfur atoms, whereas the interior tetrahedral positions are occupied by zinc atoms. Other ceramics that have a zinc blende structure are zinc telluride (ZnTe) and silicon carbide (SiC). In the crystal structure of calcium fluoride (CaF2) (Figure 2.1d), Ca2+ ions are situated at the center of cubes while the fluorine ions occupy the corner positions.
Influence of 120 MeV Si9+ ion irradiation on ZnTe semiconductor thin films
Published in Radiation Effects and Defects in Solids, 2019
Jayadev Pattar, D. PrakashBabu, K. M. Balakrishna, H. M. Mahesh
Zinc Telluride (ZnTe) is a significant II–VI compound semiconducting material which has possible applications in many solid-state devices like light-emitting diodes, solar cells and photo detectors (1–4). It has been widely considered for application as back contact material to the CdTe layer in CdTe/CdS hetero-junction solar cells (5–7). Preparation of ZnTe thin films have been reported by various techniques such as electrochemical deposition, radio frequency sputtering, two source evaporation method, molecular beam epitaxy, successive ionic layer adsorption and reaction method, thermal evaporation method (8–13), etc. Among these methods, thermal evaporation is considered as a reproducible and standard method for ZnTe thin films preparation (14–16). ZnTe thin films exhibiting stable structure, low electrical resistivity and optimum band gap are highly desired to use them in high-efficiency solar cells (17). ZnTe is also considered as one of the most attractive semiconductors for photo-electrochemical and photovoltaics solar cells because of its low affinity 3.53 eV and optimum energy gap 2.25 eV (18,19). Exposure to Swift heavy ion (SHI) radiations may alter the properties of such semiconductor devices/materials. Use of SHIs to study the stability and to alter the properties of devices/solar-cells, made for satellite applications is further an important aspect.