Electrical Joining of Paper-Based Multilayer Magneto-Resistive Sensor Stacks

With the increase in the new development of paper electronics, there is a great demand for paper-compatible and reliable electrical joining techniques. In this work, we particularly addressed the interconnecting of multilayers of paper-based magneto-electronics. We deployed three room-temperature electrical joining techniques: (i) through-paper via, (ii) mechanical caulking, and (iii) collapsible daisy chain to fabricate an anisotropic magnetoresistive five-layer thin film sensor stack for planar rotary motion sensing. We studied the interplay between the electrical joining technique and the sensor characteristics such as magnetoresistive sensitivity and asymmetries in the sensor signal within the magnetic field strength domain. Despite process complexity and the precision limitations of manual machining and positioning, deployed in this work, the sensor stacks prepared by the through-paper via technique exhibited the closest uniformity in the magnetization planes across the stack, and hence the highest cumulative magnetoresistive sensitivity and lowest unfavorable asymmetries. Last, using peeling tests, we verified the mechanical reliability of the interconnects prepared by the through-paper via and collapsible daisy chain techniques.

Structural Studies and Magnetotransport Properties of Sputtered Ni/Co Multilayers

ABSTRACTFerromagnetic/ferromagnetic Ni/Co multilayers were prepared by DC-magnetron sputtering with component layer thicknesses ranging from 40 Å down to 5 Å. Structural characterizations by x-ray diffractometry show a well-defined compositional modulation along the film growth direction and a preferred (111) crystalline orientation. A longitudinal magnetoresistance ΔR/R over 2.7% with a sensitivity of ~0.11%/Oe was measured at room temperature in small fields less than 20 Oe. The highest room temperature sensitivity obtained in this system was 0.16%/Oe. Magnetoresistive sensitivity was found to vary inversely with the number of bilayers in the multilayers. The magnetic anisotropy of the films as determined by MOKE magnetometry is correlated to the magnetoresistance and indicative of an AMR effect.