Van der Waals ferromagnetic Josephson junctions

Superconductor-ferromagnet interfaces in two-dimensional heterostructures present a unique opportunity to study the interplay between superconductivity and ferromagnetism. The realization of such nanoscale heterostructures in van der Waals (vdW) crystals remains largely unexplored due to the challenge of making atomically-sharp interfaces from their layered structures. Here, we build a vdW ferromagnetic Josephson junction (JJ) by inserting a few-layer ferromagnetic insulator Cr2Ge2Te6 into two layers of superconductor NbSe2. The critical current and corresponding junction resistance exhibit a hysteretic and oscillatory behavior against in-plane magnetic fields, manifesting itself as a strong Josephson coupling state. Also, we observe a central minimum of critical current in some JJ devices as well as a nontrivial phase shift in SQUID structures, evidencing the coexistence of 0 and π phase in the junction region. Our study paves the way to exploring sensitive probes of weak magnetism and multifunctional building-blocks for phase-related superconducting circuits using vdW heterostructures.

Accurate Determination of the Josephson Critical Current by Lock-In Measurements

Operation of Josephson electronics usually requires determination of the Josephson critical current Ic, which is affected both by fluctuations and measurement noise. Lock-in measurements allow obviation of 1/f noise, and therefore, provide a major advantage in terms of noise and accuracy with respect to conventional dc measurements. In this work we show both theoretically and experimentally that the Ic can be accurately extracted using first and third harmonic lock-in measurements of junction resistance. We derived analytical expressions and verified them experimentally on nano-scale Nb–PtNi–Nb and Nb–CuNi–Nb Josephson junctions.

Moisture-Assisted Formation of High-Quality Silver Nanowire Transparent Conductive Films with Low Junction Resistance

Silver nanowire (AgNWs) transparent conductive film (TCF) is considered to be the most favorable material to replace indium tin oxide (ITO) as the next-generation transparent conductive film. However, the disadvantages of AgNWs, such as easy oxidation and high wire-wire junction resistance, dramatically limit its commercial application. In this paper, moisture treatment was adopted, and water was dripped on the surface of AgNWs film or breathed on the surface so that the surface was covered with a layer of water vapor. The morphology of silver nanowire mesh nodes is complex, and the curvature is large. According to the capillary condensation theory, water molecules preferentially condense near the geometric surface with significant curvature. The capillary force is generated, making the wire-wire junction of AgNWs mesh bond tightly, resulting in good ohmic contact. The experimental results show that AgNWs-TCF treated by moisture has better conductivity, with an average sheet resistance of 20 Ω/sq and more uniform electrical properties. The bending test and adhesion test showed that AgNWs-TCF treated by moisture still exhibited good mechanical bending resistance and environmental stability.

Regional Intestinal Drug Absorption: Biopharmaceutics and Drug Formulation

The gastrointestinal tract (GIT) can be broadly divided into several regions: the stomach, the small intestine (which is subdivided to duodenum, jejunum, and ileum), and the colon. The conditions and environment in each of these segments, and even within the segment, are dependent on many factors, e.g., the surrounding pH, fluid composition, transporters expression, metabolic enzymes activity, tight junction resistance, different morphology along the GIT, variable intestinal mucosal cell differentiation, changes in drug concentration (in cases of carrier-mediated transport), thickness and types of mucus, and resident microflora. Each of these variables, alone or in combination with others, can fundamentally alter the solubility/dissolution, the intestinal permeability, and the overall absorption of various drugs. This is the underlying mechanistic basis of regional-dependent intestinal drug absorption, which has led to many attempts to deliver drugs to specific regions throughout the GIT, aiming to optimize drug absorption, bioavailability, pharmacokinetics, and/or pharmacodynamics. In this Editorial we provide an overview of the Special Issue "Regional Intestinal Drug Absorption: Biopharmaceutics and Drug Formulation". The objective of this Special Issue is to highlight the current progress and to provide an overview of the latest developments in the field of regional-dependent intestinal drug absorption and delivery, as well as pointing out the unmet needs of the field.

Manganite Heterojunction Photodetector with Broad Spectral Response Range from 200 nm to 2 μm

In this paper, we investigate the broad spectral photocurrent properties of the La0.67Ca0.33MnO3/Si (LCMO/Si) heterojunction from 200 nm to 2.0 μm, as the temperature increases from 95 to 300 K. We observed the junction’s uniform responsivity in the visible range and five absorption peaks at 940 nm, 1180 nm, 1380 nm, 1580 nm, and 1900 nm wavelengths. The temperature showed effective affection to the photocurrents at absorption peaks and the transition point occurred at 216 K, which was also displayed in the temperature dependence of junction resistance. On the basis of the results, we propose a possible model involving the quantum size effect at the junction interface as the mechanism. This understanding of the infrared photodetection properties of oxide heterostructures should open a route for devising future microelectronic devices.

Effect of Junction Resistance on the Percolation Resistivity of Metal Nanowire Networks

There has been significant research interest recently in random networks of one-dimensional elements such as nanotubes and nanowires. In particular, metal nanowire networks exhibit high transmittance, low sheet resistance, mechanical flexibility, and fast deposition. These unique properties make metal nanowire networks promising candidates as transparent, conductive electrodes. In this work, we perform Monte Carlo simulations to study the effect of the wire-to-wire junction resistance on the resistivity and percolation critical exponents of metal nanowire networks. We compute the network resistivity as a function of the wire-to-wire junction resistance over six orders of magnitude, ranging all the way from a junction resistance-dominated to a nanowire resistance-dominated network. We study this effect when other nanowire/device parameters are also varied. We also investigate the effect of the wire-to-wire junction resistance on the percolation critical exponents over a wide range of nanowire and device parameters. The junction resistance plays a critical role in determining both the resistivity and the critical exponents of metal nanowire networks. These studies illustrate how the junction resistance affects the macroscopic resistivity of the network. They also show that Monte Carlo simulations are an essential tool for providing insights into the percolation resistivity of transparent, conductive metal nanowire networks.