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A series of ferromagnetic-insulator granular films were prepared at room temperature with a spc350 multi-target magnetron controlled sputtering system and all of the tunneling giant magnetoresistences were measured with the conventional four probes method. Experimental results revealed that TMR depends strongly on the magnetic granule, matrix and the size distribution of magnetic granules. Accordingly, a modified phenomenological theory is presented to investigate comprehensively the effect of the magnetic granule, matrix and the size distribution of magnetic granules on the TMR. In this theory, the size distribution of granules was described by the log-normal function and all granules can be divided into three categories which have different contributions on TMR by two critical sizes: D₁(T) as the critical size distinguishing superparamagnetic granules from single domain ferromagnetic granules and D₂(T) as the critical size distinguishing the single domain from the multi-domain. The calculated results, including TMR versus applied magnetic field, measured temperature, granule size or volume fraction, are in agreement with the experiments when the single domain ferromagnetic granules play a key role in TMR for granular films, which indicates that our modified model is reasonable.

This paper focuses on the problems encountered in the production process of electronic-grade polycrystalline silicon. It points out that the characterization of electronic-grade polycrystalline silicon is mainly concentrated at the macroscopic scale, with relatively less research at the mesoscopic and microscopic scales. Therefore, we utilize the method of physical polishing to obtain polysilicon characterization samples and then the paper utilizes metallographic microscopy, scanning electron microscopy-electron backscatter diffraction technology, and aberration-corrected transmission electron microscopy technology to observe and characterize the interface region between silicon core and matrix in the deposition process of electronic-grade polycrystalline silicon, providing a full-scale characterization of the interface morphology, grain structure, and orientation distribution from macro to micro. Finally, the paper illustrates the current uncertainties regarding polycrystalline silicon.

Large-size electronic-grade polycrystalline silicon is an important material in the semiconductor industry with broad application prospects. However, electronic-grade polycrystalline silicon has extremely high requirements for production technology and currently faces challenges such as carbon impurity breakdown, microstructure and composition nonuniformity and a lack of methods for preparing large-size mirror-like polycrystalline silicon samples. This paper innovatively uses physical methods such as wire cutting, mechanical grinding and ion thinning polishing to prepare large-size polycrystalline silicon samples that are clean, smooth, free from wear and have clear crystal defects. The material was characterized at both macroscopic and microscopic levels using metallographic microscopy, scanning electron microscopy (SEM) with backscattered electron diffraction (EBSD) techniques and scanning transmission electron microscopy (STEM). The crystal structure changes from single crystal silicon core to the surface of the bulk in the large-size polycrystalline silicon samples were revealed, providing a technical basis for optimizing and improving production processes.