Gravity gradient measurement makes use of the difference between the outputs of pairs of linear accelerometers, which results in cancelling out the common mode accelerations caused by mounting platform and external environment. One of the key technologies is to match the acceleration-to-voltage or acceleration-to-current transfer functions of the pairs of the accelerometers to an extremely high degree of accuracy. The differential signals then make the gravity gradients observable. By using two pairs of the quartz-flexure accelerometers with a capacitive sensing and electrostatic closed-loop control, the electrostatic control bias voltages were trimming remotely and automatically in real time. Each pair of accelerometers was matched individually and then all four accelerometers were finally re-balanced. The experimental results show that the consistency of five digits is achieved at a noise level of ~5×10(-8) g/√Hz (1 g ≈ 9.8 m/s(2)) and the scale factors ranging from 0.25 to 0.32 V/mg. Further improvement to the achieved level of matching is limited by the intrinsic noise of the accelerometers used.
This paper investigates low temperature ohmic contact formation of Au/Sb to n-type Si substrates through AuSb/NiCr/Au metal stacks. Liquid epitaxy growth is utilized to incorporate Sb dopants into Si substrate in AuSi melt. The best specific contact resistivity achieved is 0.003 Ω ⋅ cm2 at 425 oC. Scanning electron microscopy (SEM) reveals inverted pyramidal crater regions at the metal/semiconductor interface, indicating that AuSi alloying efficiently occurs at such sites. Secondary ion mass spectroscopy (SIMS) shows that Sb atoms are successfully incorporated into Si as doping impurities during the anneal process, and the Sb doping concentration at the contact interface is found to be higher than the solid solubility limit in a Si crystal. This ohmic contacts formation method is suitable for semiconductor fabrication processes with limited thermal budget, such as post CMOS integration of MEMS.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.