The effect of surface scattering on the extraordinary Hall coefficient has been studied in thin films of nickel and granular Ni-SiO 2 mixtures. The surface scattering contributions to the Hall coefficient and longitudinal resistivity have been extracted from the respective total values. The temperature-independent linear relation between the two parameters has been found. Different scattering mechanisms need to be separated, and the applicability of the existing models for heterogeneous systems with spatially extended scattering centers should be reexamined.

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The electron-par'amagnetic-resonance signal that appears when Si is crushed, cleaved, or abraded is shown to be proportional to the areas of microcracks induced in the specimen. These are shown to be more prevalent than previously realized. Detailed consideration shows that a wide variety of previously inexplicable data can now be understood. These include some effects of oxygen and hydrogen, variability of signal width, effects of abrasive particle size, and kind of cleavage. The origin of the unpaired electrons is considered and it is concluded that they may be in localized states on the surfaces of the microcracks, such states being apparently a case of Anderson localization. The atoms on the crack surfaces are subject to spatially varying overlap forces and stress fields whose energy range exceeds the normal bandwidth, thus inducing localization. The temperature dependence of the paramagnetism of such states is discussed, including correlation corrections, and shown to yield approximately T ', as observed experimentally. A similar explanation applies to Ge. Cleancleaved Si surfaces display negligible surface paramagnetism due to pairing of surface electrons on alternate atom sites. The results suggest that for amorphous Si and Ge, localized states on the surfaces of small atom aggregates should be considered as a possible source of the observed paramagnetism.

This paper reports on the mechanical and piezoresistance characterization of hydrogenated amorphous and nanocrystalline silicon thin films deposited by hot-wire chemical vapor deposition (HWCVD) and radio-frequency plasma-enhanced chemical vapor deposition (PECVD) using substrate temperatures between 100 and 250 °C. The microtensile technique is used to determine film properties such as Young’s modulus, fracture strength and Weibull parameters, and linear and quadratic piezoresistance coefficients obtained at large applied stresses. The 95%-confidence interval for the elastic constant of the films characterized, 85.9 ± 0.3 GPa, does not depend significantly on the deposition method or on film structure. In contrast, mean fracture strength values range between 256 ± 8 MPa and 600 ± 32 MPa: nanocrystalline layers are slightly stronger than their amorphous counterparts and a pronounced increase in strength is observed for films deposited using HWCVD when compared to those grown by PECVD. Extracted Weibull moduli are below 10. In terms of piezoresistance, n-doped radio-frequency nanocrystalline silicon films deposited at 250 °C present longitudinal piezoresistive coefficients as large as −(2.57 ± 0.03) × 10−10 Pa−1 with marginally nonlinear response. Such values approach those of crystalline silicon and of polysilicon layers deposited at much higher temperatures.

This paper reports on a novel CMOS-based silicon microprobe for high-density intracortical stress mapping. In contrast to existing systems, square p-type field effect transistors (FET) with four source/drain contacts (piezo-FETs) are integrated on the slender, needle-like probe shaft. In total, 345 stress sensors are arranged in five columns (x/y-pitch of 51.4/26.6 µm) along the 180-µm-wide shaft. Measuring in-plane normal stress in silicon neural probes is envisioned to avoid probe fracture during insertion and to evaluate the probe deflection caused by brain motion after insertion. The combination with switchable electrodes will enable the simultaneous neural recording of brain activity. The paper presents the probe concept, the post-CMOS fabrication process, the piezo-FET characterization, and measurements demonstrating stress mapping in a brain model.