Metal Junctions Research Articles

Electronic properties of tetrathiafulvalene-modified cyclic-β-peptide nanotube.

Cyclic tri-β-peptide having tetrathiafulvalene (TTF) at the side chain was synthesized to prepare a peptide nanotube aligning TTF side chains along the nanotube. The polarized light microscopic observations revealed crystallization of the cyclic peptide by the vapor diffusion method. Fourier-transform infrared and electron diffraction measurements of the crystals clarified formation of homogeneous hydrogen bonds making a columnar structure with a layer spacing of 4.9 Å. Electronic measurements of the peptide crystals on a gold mica substrate were carried out by the current sensing AFM. The current-voltage curves showed a rectification behavior, whose profile was consistent with a metal and p-type semiconductor junction. The p-type property is supported by the first principle calculations, which showed the HOMO orbital delocalizing fully over the plane of the TTF ring with the energy level of -5.1 eV. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 275-282, 2016.

Zeeman effects on the tunneling spectra of a ferromagnetic d-wave superconductor in contact with a quantum wire

We study tunneling conductance in a quantum wire–insulator–ferromagnetic d-wave superconductor junction. The results show that exchange field of superconductor has a strong impact on tunneling spectra depending on the junction parameters. We have found a gap like structure in the tunneling limit when we have an interface normal to the (100) axis of superconductor. In the case of (110) axis of superconductor, there is not any zero- bias conductance peaks in tunneling spectra. For a metallic junction the dips disappear.

Spin-polarized current in Zeeman-split d-wave superconductor/quantum wire junctions

Abstract We study a thin-film quantum wire/unconventional superconductor junction in the presence of an intrinsic exchange field for a d-wave symmetry of the superconducting order parameter. A strongly spin-polarized current is generated due to an interplay between Zeeman splitting of bands and the nodal structure of the superconducting order parameter. We show that strongly spin-polarized current is achievable for both metallic and tunnel junctions. This is because of the presence of a quantum wire (one-dimensional metal) in our junction. While in two-dimensional junctions with both conventional [F. Giazotto, F. Taddei, Phys. Rev. B 77 (2008) 132501] and unconventional [J. Linder, T. Yokoyama, Y. Tanaka, A. Sudbo, Phys. Rev. B 78 (2008) 014516] pairing states, highly spin polarized current takes place just for a tunnel junction. Also, the obtained spin-polarized current is tunable in sign and magnitude in terms of exchange field and applied bias voltage.

Time-dependent Landauer—Büttiker formalism for superconducting junctions at arbitrary temperatures

We discuss an extension of our earlier work on the time-dependent Landauer- Buttiker formalism for noninteracting electronic transport. The formalism can without complication be extended to superconducting central regions since the Green's functions in the Nambu representation satisfy the same equations of motion which, in turn, leads to the same closed expression for the equal-time lesser Green's function, i.e., for the time-dependent reduced one-particle density matrix. We further write the finite-temperature frequency integrals in terms of known special functions thereby considerably speeding up the computation. Simulations in simple normal metal - superconductor - normal metal junctions are also presented.

Detection of a magnetic bead by hybrid nanodevices using scanning gate microscopy

Hybrid ferromagnetic(Py)/non-magnetic metal(Au) junctions with a width of 400 nm are studied by magnetotransport measurements, magnetic scanning gate microscopy (SGM) with a magnetic bead (MB) attached to the probe, and micromagnetic simulations. In the transverse geometry, the devices demonstrate a characteristic magnetoresistive behavior that depends on the direction of the in plane magnetic field, with minimum/maximum variation when the field is applied parallel/perpendicular to the Py wire. The SGM is performed with a NdFeB bead of 1.6 μm diameter attached to the scanning probe. Our results demonstrate that the hybrid junction can be used to detect this type of MB. A rough approximation of the sensing volume of the junction has the shape of elliptical cylinder with the volume of ∼1.51 μm3. Micromagnetic simulations coupled to a magnetotransport model including anisotropic magnetoresistance and planar Hall effects are in good agreement with the experimental findings, enabling the interpretation of the SGM images.

Electrical characterization of benzenedithiolate molecular electronic devices with graphene electrodes on rigid and flexible substrates

We investigated the electrical characteristics of molecular electronic devices consisting of benzenedithiolate self-assembled monolayers and a graphene electrode. We used the multilayer graphene electrode as a protective interlayer to prevent filamentary path formation during the evaporation of the top electrode in the vertical metal–molecule–metal junction structure. The devices were fabricated both on a rigid SiO2/Si substrate and on a flexible poly(ethylene terephthalate) substrate. Using these devices, we investigated the basic charge transport characteristics of benzenedithiolate molecular junctions in length- and temperature-dependent analyses. Additionally, the reliability of the electrical characteristics of the flexible benzenedithiolate molecular devices was investigated under various mechanical bending conditions, such as different bending radii, repeated bending cycles, and a retention test under bending. We also observed the inelastic electron tunneling spectra of our fabricated graphene–electrode molecular devices. Based on the results, we verified that benzenedithiolate molecules participate in charge transport, serving as an active tunneling barrier in solid-state graphene–electrode molecular junctions.

Coherent Epitaxy of a Ferroelectric Heterostructure on a Trilayered Buffer for Integration into Silicon

Coherent-epitaxial ferroelectric BaTiO3 films are grown on Si by using a SrTiO3/SrO1+δ/YSZ trilayered buffer. The SrTiO3/SrO1+δ interface produces significant improvements in the BaTiO3/(La,Sr)MnO3 heterostructure, including perfect (001) orientation, high crystallinity, and sharp and uniform interfaces. The BaTiO3-based metal/insulator (ferroelectric)/metal junctions exhibit a remanent polarization as high as 17 μC cm–2. Nonvolatile electroresistance is also demonstrated in patterned junctions with ultrathin BaTiO3 layers. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Microstructure characterization and electrical transport of nanocrystalline Zn0.90Mn0.10O semiconductors synthesized by mechanical alloying

We report a comprehensive study of dc and ac conductivity, dielectric relaxation and capacitance–voltage characteristics of Mn doped ZnO nanocrystalline semiconductors prepared by mechanical alloying. Samples are characterized by HRTEM and XRD. Direct current conductivity increases with the increase in temperature and the thermal behavior of electrical dc conductivity for the investigated samples can be described by adiabatic polaronic hopping model. The frequency dependent conductivity obeys a power law σ′(f)∝fsTn. The temperature exponent n strongly depends on frequency. Analysis of the temperature dependence of frequency exponent s suggests a transformation from large polaron to small polaron conduction model with increase in temperature. Considering electric modulus the dielectric properties of the samples have been explained. Capacitance–voltage characteristic suggests the formation of Schottky diode between metallic electrode and semiconductor junction and diode parameter shows anomalous behavior with increasing milling time.

Evidence for a hopping mechanism in metal|single molecule|metal junctions involving conjugated metal-terpyridyl complexes; potential-dependent conductances of complexes [M(pyterpy)2]2+ (M = Co and Fe; pyterpy = 4'-(pyridin-4-yl)-2,2':6',2''-terpyridine) in ionic liquid.

Extensive studies of various families of conjugated molecules in metal|molecule|metal junctions suggest that the mechanism of conductance is usually tunnelling for molecular lengths < ca. 4 nm, and that for longer molecules, coherence is lost as a hopping element becomes more significant. In this work we present evidence that, for a family of conjugated, redox-active metal complexes, hopping may be a significant factor for even the shortest molecule studied (ca. 1 nm between contact atoms). The length dependence of conductance for two series of such complexes which differ essentially in the number of conjugated 1,4-C6H4- rings in the structures has been studied, and it is found that the junction conductances vary linearly with molecular length, consistent with a hopping mechanism, whereas there is significant deviation from linearity in plots of log(conductance) vs. length that would be characteristic of tunnelling, and the slopes of the log(conductance)-length plots are much smaller than expected for an oligophenyl system. Moreover, the conductances of molecular junctions involving the redox-active molecules, [M(pyterpy)2]2+/3+ (M = Co, Fe) have been studied as a function of electrochemical potential in ionic liquid electrolyte, and the conductance-overpotential relationship is found to fit well with the Kuznetsov-Ulstrup relationship, which is essentially a hopping description.

The effect of diamond like carbon coating on fretting corrosion and wear at the modular head-stem junction of metal on metal total hip replacements

The effect of diamond like carbon coating on fretting corrosion and wear at the modular head-stem junction of metal on metal total hip replacements

Organometallic molecular wires as versatile modules for energy-level alignment of the metal-molecule-metal junction.

The organometallic Ru molecular wires 1-3 Ru(PR3)4(C[triple bond, length as m-dash]CC5H5N)2 [(PR3)4 = (dppe)2 (1), [P(OMe3)]4 (2), and (dmpe)2 (3)] show significantly higher conductance compared to their organic counterpart, 1,4-dipyridyl butadiyne (4). CV and UV-Vis measurements and DFT calculations suggest that the high-lying HOMOs of the Ru wires are the key factor for the high conductance.

Quantum spin transport and dynamics through a ferromagnetic/normal metal junction

We study the spin transport in the low temperature regime (often referred to as the precession-dominated regime) between a ferromagnetic Fermi liquid (FFL) and a normal metal metallic Fermi liquid (NFL), also known as the F/N junction, which is considered as one of the most basic spintronic devices. In particular, we explore the propagation of spin waves and transport of magnetization through the interface of the F/N junction where nonequilibrium spin polarization is created on the normal metal side of the junction by electrical spin injection. We calculate the probable spin wave modes in the precession-dominated regime on both sides of the junction especially on the NFL side where the system is out of equilibrium. Proper boundary conditions at the interface are introduced to establish the transport of the spin properties through the F/N junction. A possible transmission conduction electron spin resonance (CESR) experiment is suggested on the F/N junction to see if the predicted spin wave modes could indeed propagate through the junction. Potential applications based on this novel spin transport feature of the F/N junction are proposed in the end.

Modular Head Mismatch in THA

Modular femoral heads have been used successfully since the mid-1980s in total hip arthroplasty. The use of metallic modular junctions presents a unique set of advantages and problems for use in total hip arthroplasty (THA). The separation of the head from the stem by a Morse taper has provided many benefits on the precision and balancing the reconstructed joint. Historically few complications have been reported for the modular Morse taper connection between the femoral head and trunnion of the stem in metal-on-polyethylene bearings. However, the risks or concerns are a little harder to identify and deal with. Certainly corrosion, and fatigue failure are the two most prevalent concerns but now the specifics of fretting wear and corrosive wear increasing particulate debris and the potential biological response is having an impact on the design and potential longevity of the reconstructed hip. This paper is dealing with a simpler consequence of head/stem modularity. Modular head mismatch to the socket bearing articulation.Two patients by two different surgeons at two different hospitals underwent cementless THA. Both patients were female and both presented with degenerative changes to the hip articulation. Both patients underwent hip replacement via a direct anterior approach using a standard hemispherical porous coated shell. One patient had a ceramic on ceramic bearing and the other had a ceramic head on a polyethylene liner. Both patients had a 32 mm inside diameter liner implanted and both had a 36 mm ceramic femoral head. The ceramic on ceramic mismatch was not recognized until the second office visit at eight weeks. The ceramic poly mismatch was not recognized until first office visit at six weeks. Both underwent correction surgery.These two cases demonstrate human mistakes can be made and steps need to be established to prevent future mistakes of this nature.

Closing the proximity gap in a metallic Josephson junction between three superconductors

We describe the proximity effect in a short disordered metallic junction between three superconducting leads. Andreev bound states in the multi-terminal junction may cross the Fermi level. We reveal that for a quasi-continuous metallic density of states, crossings at the Fermi level manifest as closing of the proximity-induced gap. We calculate the local density of states for a wide range of transport parameters using quantum circuit theory. The gap closes inside an area of the space spanned by the superconducting phase differences. We derive an approximate analytic expression for the boundary of the area and compare it to the full numerical solution. The size of the area increases with the transparency of the junction and is sensitive to asymmetry. The finite density of states at zero energy is unaffected by electron-hole decoherence present in the junction, although decoherence is important at higher energies. Our predictions can be tested using tunneling transport spectroscopy. To encourage experiments, we calculate the current-voltage characteristic in a typical measurement setup. We show how the structure of the local density of states can be mapped out from the measurement.

Analysis of electromagnetic multi-scale structure and non-linear effects

The microstructures and the electrical contact property may affect the performance of the macro scale objects,and the passive intermodulation( PIM) problems cannot be directly calculated by frequencydomain methods. Firstly,the Floquet's theorem combined with the full-wave method was proposed to analyze the electrical performance of the multi-scale structure with periodic microstructures. Secondly,an equivalent circuit model of non-linear metallic junctions coupled with full-wave frequency domain method was adopted to analyze the PIM problems of multi-scale structure. The numerical results show that the method proposed can evaluate the influence of microstructure on the performance of macrostructure,and eliminate the accumulation of computational error appeared in the time domain method which is unacceptable in electrically large objects.

Conductance of a Single Magnesium Porphine Molecule on an Insulating Surface

Using first-principles calculations based on density functional theory and nonequilibrium Green’s function formalism, we study the electron transport through a magnesium porphine molecule adsorbed on an ultrathin NaCl bilayer. The conductance of the tip–vacuum–molecule–NaCl–metal junction depends on the orientation of the molecule on the insulating surface and the tip position above the molecule, which is mediated largely by the molecular pz orbital. The movement of molecule results in a perturbation to the spatial extension of these orbitals, leading to different conductions.

Diagnóstico de la Planta de Lixiviación de la oficina Salitrera Santa Laura en Chile. Patrimonio de la Humanidad

The Santa Laura Saltpeter Work, which is nowadays the place where the most complete industrial infrastructure of the nitrate processing period is maintained, has a Leaching Tower that is considered by its uniqueness, the icon of the former nitrate industry in Chile. This impressive structure, built mostly in Oregon Pine wood ( Pseudotsuga menziesii ) with metal junctions, unfortunately bears, after the plant stopped producing nitrate and iodine, the impact of its productive past and subsequent human actions because of neglect and lack of maintenance. This report, based on a visual, instrumental and structural inspection, is a diagnosis of the current condition of the building. The results indicate that the elements of the structure, with some exceptions, are in good condition and without changes in their mechanical properties. Structural analysis determined that the plant behavior is favorable, being able to withstand a seismic event of importance.

Simulation of Electromagnetic Performance on Mesh Reflector Antennas: Three-Dimensional Mesh Structures With Lumped Boundary Conditions

Reflector antennas with mesh surfaces have been extensively used in satellite antenna systems. The electrical contact at the metal–insulator–metal (MIM) junction points may cause the degradation of reflectivity performance, and the concept of MIM junctions is mainly used for the analysis of passive intermodulation (PIM) arising from metallic contact in the practical antennas. In this work, a three-dimensional (3-D) modeling of mesh surfaces is presented, which introduced impedance connections at the wire junctions of metallic contact area. The electrical contact model of impedance connections is equivalent to a circuit model, which is considered as lumped boundary condition extended to the modeling of mesh. The planar mesh reflection coefficients are constructed using a full-wave frequency domain method with Floquet mode expansion. To calculate the electrical performance of curved mesh antenna, a solid surface with an equivalent loss is adopted to replace the mesh surfaces. The reflection coefficients of the equivalent loss material are the same as for the mesh surfaces. The analysis of the planar mesh reflectors with three different connections (solid surface, perfect contact, and lumped connection) at junction points is performed as an example for the proposed model. The results demonstrate the usefulness of the model in accurate performance prediction of mesh reflector antennas. Finally, a mesh reflector antenna with 3-D mesh structures is analyzed to predict the electrical performance of the antenna.

Metallic Modular Taper Junctions in Total Hip Arthroplasty

The emergence of modularity in total hip arthroplasty (THA) in the 1980s and 1990s was based on the fact that the benefit of these design features outweighed the risk. The use of metallic modular junctions presents a unique set of advantages and problems for use in THA. The advantages include improvement in fit and fill of the implant to bone, restoration of joint mechanics, reduced complications in revision surgery and reduction of costly inventory. However, the risks or concerns are a little harder to identify and deal with. Certainly corrosion, and fatigue failure are the two most prevalent concerns but now the specifics of fretting wear and corrosive wear increasing particulate debris and the potential biological response is having an impact on the design and potential longevity of the reconstructed hip. Material and designs are facing a shorter life expectancy than what was previously thought, mostly due to an increasing level of physical activity by the patient. Because there are no accurate laboratory test whereby the service life and performance of these implants can be predicted, early controlled clinical evaluations are necessary. Early publication of testing and clinical impressions should be encouraged in an attempt to reduce exposure to potential at risk patients, implants and material. The reduction and possible elimination of risks will require a balancing of all the variables requiring a multidisciplinary endeavor.This paper is designed to review the risk factors, and benefits of modular junctions in total hip arthroplasty (THA). Also some basic engineering principals that can reduce risk factors and improve functionality of modular junctions.

A high precision apparatus for intracellular thermal response at single-cell level

In this work, a nanoprobe that is highly thermo-sensitive to tiny temperature changes was prepared based on a thermocouple metal junction. A series of electro-element apparatuses were integrated to accomplish single-cell temperature measurement. The temperature measurement probe (TMP) was constructed by tungsten (W), polyurethane (PU), and platinum (Pt). The tip size of TMP was characterized at less than 500 nm, and the tip angle was between 10 and 20° with the resistance in the range of 500 to 1500 Ω. The single-cell temperature measurement probes were calibrated and calculated with a Seebeck coefficient ranging from 6 to 8 μV °C−1 at a precision of 0.1 °C. Monitoring the temperature at a single-cell level by inserting the TMP in marine lung epithelia (MLE)-12 cells displayed that the stimulation of lipopolysaccharide (LPS) and cobalt chloride induced different single-cell temperature fluctuation. This investigation could help reveal complex cellular functions and develop novel diagnoses.