On-chip measurement of the Brownian relaxation frequency of magnetic beads using magnetic tunneling junctions

We demonstrate the detection of the Brownian relaxation frequency of 250 nm diameter magnetic beads using a lab-on-chip platform based on current lines for exciting the beads with alternating magnetic fields and highly sensitive magnetic tunnel junction MTJ sensors with a superparamagnetic free layer. The first harmonic out-of-phase component of the MTJ response gives the imaginary part of the magnetic bead susceptibility, which peaks at the Brownian relaxation frequency. This work paves the way to on-chip implementation of Brownian magnetorelaxometry in innovative “lab-on-a-bead” assays for biomolecular recognition

Electrical properties of TaN–Cu nanocomposite thin films

TaN–Cu nanocomposite thin films used as materials for TFR (thin film resistor) were prepared by reactive co-sputtering of Ta and Cu in the plasma of N2 and Ar. After deposition, the films were annealed using rapid thermal processing (RTP) at 400 °C for 2, 4, 8 min, respectively to induce the nucleation and grain growth of Cu. The results reveal that temperature coefficient of resistivity (TCR) values will increase with the increase of Cu content for both the as-deposited and annealed films. The increase of nitrogen will result in higher resistivity and more negative TCR. At a constant nitrogen flow rate, the resistivity and TCR may increase or decrease with the increase of annealing time depending on the Cu content. In general, to reach near-zero TCR value, more copper is needed to compensate the negative effect caused by Ta–N. Thus, electrical properties of thin films can be characterized as functions of N2 flow rate, Cu concentration and annealing time

Durability of Solid Oxide Cells

In recent years extended focus has been placed on monitoring and understanding degradation mechanisms in both solid oxide fuel cells and solid oxide electrolysis cells. The time-consuming nature of degradation experiments and the disparate conclusions from experiment reproductions indicates that not all degradation mechanisms are fully understood. Traditionally, cell degradation has been attributed to the materials, processing and cell operating conditions. More recently, focus has been placed on the effect of raw material and gas impurities and their long term effect on cell degradation. Minor impurities have been found to play a significant role in degradation and in some cases can overshadow the cell operation condition related degradation phenomenon. In this review, several degradation diagnostic tools are discussed, a benchmark for a desirable degradation rate is proposed and degradation behaviour and mechanisms are discussed. For ease of navigation, the review is separated into the various cell components - fuel electrode, electrolyte and oxygen electrode. Finally, nanoparticle impregnate stability is discussed