Abstract: In a method for preparing silicon-on-insulator, the first etching stop layer, the second etching stop layer, and the device layer are formed bottom-up on the p-type monocrystalline silicon epitaxial substrate, where the first etching stop layer is made of intrinsic silicon, the second etching stop layer is made of germanium-silicon alloy, and the device layer is made of silicon. After oxidation, bonding, reinforcement, and grinding treatment, selective etching is performed. Through a first selective etching to p+/intrinsic silicon, the thickness deviation of the first etching stop layer on the second etching layer is controlled within 100 nm, and then through the second etching and the third etching, the thickness deviation and the surface roughness of the finally prepared silicon-on-insulator film can be optimized to less than 5 nm and less than 4 ?, respectively, so as to realize the flatness of the silicon-on-insulator film.

Abstract: A SOI wafer is disclosed. The SOI wafer may be characterized by surface roughness of a top silicon layer of the SOI wafer is less than 4 ?, thickness uniformity of the top silicon layer is within ±1%, and a total number of particles on a surface of the top silicon layer of the SOI wafer, measured with setting of 37 nm of SPx detection threshold, is less than 100.

Abstract: A sealed core-coil assembly in a submersible transformer includes a coil assembly having an inner coil with inner, outer, upper, and lower surfaces, and an outer coil with inner, outer, upper, and lower surfaces, a core assembly including a core window and core column of a magnetically-permeable material, the core column and core window having inner side surfaces, and an expandable sealing member including an inner cavity that is fillable or evacuatable so that a compliant insulation material is positioned in the inner cavity to block passage of water and prevent the formation of a loop of water, which otherwise would act like an electrical short in a submerged transformer.

Abstract: A sealed core-coil assembly includes a coil assembly having an inner coil with inner, outer, upper, and lower surfaces, and an outer coil with inner, outer, upper, and lower surfaces, a core assembly including a core window and core column of a magnetically-permeable material, the core column and core window having inner side surfaces, and an expandable sealing member including an inner cavity that is fillable or evacuatable. An expandable sealing member is provided between: one or more inner side surfaces of the core column and one or more inner surfaces of the inner coil, the outer surface of the inner coil and the inner surface of the outer coil, and between the upper and lower surfaces of the inner and outer coils and the inner side surfaces of the core window. Core-coil assemblies, sealing assemblies, and sealing methods are provided, as are numerous other aspects.