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Growth of Superconducting Single Crystals
Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2023
Debra L. Kaiser, Lynn F. Schneemeyer
The largest and highest quality La2–xSrxCuO4 (0 ≤ x ≤ 0.3) and La2–xBaxCuO4 (0.06 ≤ x ≤ 0.09) crystals have been grown by the crucibleless TSFZ approach [31, 57–63]. The feed and seed rods are stoichiometric or slightly CuO-rich sintered, polycrystalline La2–xAxCuO4 (A = Sr or Ba) and the solvent rods are composed of 55–85 mole % CuO with a balance of La2–xAxCuO4. Growth runs were typically performed under an oxygen pressure of 0.2–1 MPa (2–10 atm). A modified TSFZ method which uses no solvent rod has also been reported [62]. Typical single crystal boule dimensions are 5–7 mm in diameter and 10–15 mm in length. Sharp superconducting transitions at Tc = 33–38 K for La0.85Sr0.15CuO4 and Tc = 27–29 K for La2–xBaxCuO4 (0.065 ≤ x ≤ 0.09) were obtained, mostly for the as-grown state. These transitions are higher than those obtained in crystals prepared by flux growth or TSSG methods where it was likely that contamination by the crucible caused reduced Tc values. The TSFZ method has also been used to grow crystals of La2–xCaxCuO4 (0.075 ≤ x ≤ 0.09) with broad transitions at Tc = 15 K [63] and (La,Sm,Sr)2CuO4 with broad transitions at Tc = 17 K after oxygen annealing [64].
Focal Plane Arrays
Published in Antoni Rogalski, Zbigniew Bielecki, Detection of Optical Signals, 2022
Antoni Rogalski, Zbigniew Bielecki
Innovations and progress in FPA fabrication are dependent on adjustments to the material growth parameters. Usually, in-house growth has enabled manufacturers to maintain the highest material quality and to customise the layer structures for multiple applications. For example, since HgCdTe material is critical to many principal product lines, and comparable material is not available externally, most global manufacturers continue to supply their own wafers. Figure 12.10 shows process flow for integrated infrared FPA manufacturing. As is shown, boule growth starts with the raw materials, polycrystalline components. In the case of HgCdTe FPA process, polycrystalline ultrapure CdTe and ZnTe binary compounds are loaded into a carbon-coated quartz crucible. The crucible is mounted into an evacuated quartz ampoule, which is placed in a cylindrical furnace. Large-crystal CdZnTe boules are produced by mixing and melting the ingredients, followed by recrystallising with the vertical gradient freeze method. Their standard diameters reach 125 millimetres. The boule substrate material is then sawn into slices, diced into squares, and polished to prepare the surface for epitaxial growth. Typical substrate sizes up to 8 cm×8 cm have been produced. The HgCdTe layers are usually grown on top of the substrate by MBE or MOCVD. In the case of MOCVD epitaxial technology also large-size GaAs substrates are used. The selection of substrate depends on the specific application. The entire growth procedure is automated, with each step being programmed in advance.
Electro-Optical Scanners
Published in Gerald F. Marshall, Glenn E. Stutz, Handbook of Optical and Laser Scanning, 2018
Timothy K. Deis, Daniel D. Stancil, Carl E. Conti
A large class of ferroelectric materials have the form A1+B5+O3 or A2+B4+O3, and are related to the mineral perovskite (CaTiO3). Several of these materials are in mass production for devices based on their piezoelectric properties, such as LiNbO3 for surface acoustic wave filters, which are found in cell phones and a host of other signal processing applications. Czochralski growth is the typical practice, with boule diameters approaching 15 cm for LiNbO3, although 7.5 and 10 cm is more common. During the processing of crystal boules, they are typically poled to form a single domain throughout by heating to a point near the Curie temperature and then applying a DC electric field, which is maintained during the cooldown. This ensures that all crystal domains have uniform orientation—a critical consideration for good optical quality of the ensuing device.
Thermal diffusivity and thermal conductivity in layered ferrielectric materials M1+M3+P2(S,Se)6 (M1+ = Cu, Ag; M3+ = In, Bi)
Published in Phase Transitions, 2019
V. Liubachko, A. Oleaga, A. Salazar, A. Kohutych, K. Glukhov, A. Pogodin, Yu. Vysochanskii
A directed melt crystallization method was used due to the congruent melting character of the compounds and a comparatively low dissociation vapor pressure for the synthesis of the single crystals. The synthesis of the complex ternary hexachalcohipodiphosphates CuInP2(S, Se)6, AgInP2(S, Se)6 and CuBiP2Se6 was carried out from elementary components Cu (99.999%), Ag (99.999%), In (99,999%), Bi (99.9999%), P (99.9999%), S (99.999%), Se (99.9996%). The samples were cut from the single crystal boules, and prepared as thin plane parallel slabs whose surfaces are either parallel to the layers or perpendicular to them. As a consequence, there are, for each composition, two oriented samples to measure.