Sep 17, 2014

Plastically deformed Ge-crystal wafers as elements for neutron focusing monochromator

Plastically deformed Ge-crystal wafers that have the cylindrical shape with a large curvature were characterized by neutron diffraction. The box-type rocking curve of Bragg reflection with the angular width ofΓbox≃2° in FWHM, which is observable in the monochromatic neutron diffraction, results in an enhancement in the angle-integrated intensity (Iθ). Besides, Iθ efficiently increases by stacking such Ge wafers. In the course of white neutron diffraction, the reflected-beam width near the focus point becomes sharper than the initial beam width. Further, the dependence of the horizontal beam width on the distance between the sample and detector is quantitatively explained by taking account of the large Γbox, the small mosaic spread of η≃0.1°, and the thickness of the wafers. On the basis of these characterizations, use of plastically deformed Ge wafers as elements for high-luminance neutron monochromator is proposed.


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  • Neutron monochromator crystal
  • Neutron beam focus,crystal wafer,crystal wafer facebook,wafer crystal defects
  • Source:Sciencedirect

Sep 4, 2014

A high-performance bulk mode single crystal silicon microresonator based on a cavity-SOI wafer


A cavity-silicon-on-insulator (SOI)-based single crystal silicon (SCS) micromechanical resonator has been demonstrated in this paper. The most distinguishing feature of this method is that it solves the restrictions of being released from the sacrificial layer. The resonator structures can be fabricated and released in one step using dry anisotropic etching. The differential drive, single-ended sense configuration is implemented to measure the electrical characterization of the fabricated resonator. The fabricated square plate resonator has been excited in the Lame´ mode at a resonant frequency of 4.126 MHz and exhibits a quality factor (Q) as high as 5.49× 106 at a pressure of 0.05 mbar. This result corresponds to a frequency–Q product of 2.27× 1013, which is the highest value demonstrated to date for silicon-based resonators as far as we know. The dependence of Q and resonant frequency on the operating pressure is measured and characterized. The temperature stability of the device is also demonstrated, with the temperature coefficient of resonant frequency less than −20.8 ppm °C−1 in the temperature range from −10 to 60 °C. The high performance of the resonator not only benefits from the superior performance of SCS as a mechanical material, but also the merit of the cavity-SOI structure.

Key words:
crystal sapphire wafer
single crystal wafer

wafer crystal defects
piezo crystal wafers
single crystal silicon wafer

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