We investigated spintronic strain-gauge sensors (Spin-SGSs) based on magnetic tunnel junctions (MTJs). To enhance the strain sensitivity of Spin-SGSs, which is defined as the gauge factor = (ΔR/R)/Δε, we investigated MgO-MTJs with an amorphous CoFeB sensing layer that exhibits high magnetostriction and soft magnetic properties. To maintain the amorphous structure of the CoFeB sensing layer even after post annealing, we applied a MgO capping layer (MgO-cap) to the CoFeB sensing layer and compared it with a Ta capping layer (Ta-cap). After post annealing at 320 °C, the CoFeB sensing layer with a MgO-cap maintained a low coercivity of 3 Oe, whereas that with a Ta-cap exhibited a high coercivity of 25 Oe. Microstructure analysis revealed that the CoFeB sensing layer with the MgO-cap has an amorphous structure because boron remains in the CoFeB sensing layer even after post annealing. The gauge factor for the Spin-SGS with the MgO-cap was 4016, which was four times larger than 942 for the Spin-SGS with the Ta-cap.
We report a novel palladium (Pd)-based micro electro-mechanical system (MEMS) capacitive hydrogen gas sensor that has an inverted T-shaped electrode and a ring-shaped Pd alloy layer, which enable high sensitivity and low power consumption. Thanks to these structures, deformation of the membrane as a result of hydrogen absorption can be efficiently transduced to capacitance change. The capacitance change of the proposed sensor is found to be three times larger than that of the conventional structure. Prototype sensors were fabricated by a CMOS-compatible surface micromachining process. The proposed sensor offers a broad design window for attaining high sensitivity. Finally, we show that our sensor provides fast response, is hysteresis-free, and has excellent hydrogen selectivity characteristics despite not employing a heater by using PdCuSi metallic glass.
In this article, the quasistatic and dynamic tensile properties of aluminum-silicon-copper (Al-Si-Cu) alloy films are described. The films were deposited by sputtering onto thermally oxidized Si wafers, and then half of the wafers were heat treated at 623 K in nitrogen gas for 1 h. Specially developed environment-controlled uniaxial tensile test equipment was used to carry out the quasistatic tensile test, stress relaxation test, and cyclic loading test at temperatures ranging from room temperature (RT) to 573 K in high vacuum, and the influence of annealing on the mechanical characteristics was investigated. The Young's modulus did not show annealing dependency. The mean value was 65 GPa at RT, and gradually decreased with increasing test temperature. The yield stresses of nonannealed and annealed films were 168.5 and 129.6 MPa, respectively, which also decreased with temperature rise. In stress relaxation test results, creep exponents in respective films were obtained from curve fitting using the Norton law, which indicated that creep deformation was restricted by annealing. The cyclic loading test was performed under stress-and displacement-amplitude-constant modes. The stress-amplitudeconstant mode test provided creep deformation acceleration to failure, whereas the displacementamplitude-constant mode test showed a gradual drop of stress amplitude. The stress-amplitude change was compared with stress relaxation curves; consequently, the creep deformation was dominant to the degradation of Al-Si-Cu films subjected to cycling loading with constant displacement amplitude.
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.