Junction Parameters Research Articles

Reduced Critical Current Spread in Planar MgB2 Josephson Junction Array Made by Focused Helium Ion Beam

We have fabricated series arrays of closely spaced planar Josephson junctions on MgB2 films using a 30 keV focused helium ion beam. Uniformity of junction parameters within the arrays is sufficient for achieving phase-lock into an applied microwave signal, and flat giant Shapiro steps are observed. The spread in critical current of a 60-Josephson junction array is estimated to be less than 3.5%, significantly better than reported in MgB2 junctions fabricated by other techniques. These results demonstrate the potential of the focused He <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ion beam irradiation technique in MgB2 Josephson multi-junction circuit applications such as quantum voltage standards.

Ultrawideband graphene three-port circulator for THz region

The suggested circulator is formed by a concave pattern graphene junction and three waveguides symmetrically connected to it. The graphene is supported by SiO2/Si layers. The circulation behavior is based on the nonsymmetry of the graphene conductivity tensor which appears due to magnetization by a DC magnetic field applied normally to the graphene plane. The symmetrical mode propagating in the nonmagnetized graphene waveguide, is transformed in magnetized region to an edge-guided one providing the propagation from one port to another port and isolating the third port. The device characteristics depend on the physical parameters of the graphene junction, its dimensions and parameters of the substrate. We discuss a choice of these parameters to maximize the frequency band and isolation level and to minimize the losses and the applied DC magnetic field. The theoretical arguments are confirmed by full-wave computations. In an example, we demonstrate that the circulator can have the frequency band of 42% (from 2.75THz to 4.2THz), with the isolation higher than 17 dB and the insertion losses better that 2dB, provided by the biasing DC magnetic field 1.5T and the chemical potential of graphene 0.15eV.

Tu1202 – Key Parameters of Esophagogastric Junction (EGJ) Impedance Planimetry for Non-Obstructive Dysphagia: Comparing Patients with Achalasia, Egj Outflow Obstruction, and Normal Integrated Relaxation Pressure

Tu1202 – Key Parameters of Esophagogastric Junction (EGJ) Impedance Planimetry for Non-Obstructive Dysphagia: Comparing Patients with Achalasia, Egj Outflow Obstruction, and Normal Integrated Relaxation Pressure

Quantum properties of a strongly driven Josephson junction

A Josephson junction embedded in a dissipative circuit can be externally driven to induce nonlinear dynamics of its phase. Classically, under sufficiently strong driving and weak damping, dynamic multi-stability emerges associated with dynamical bifurcations so that the often used modeling as a Duffing oscillator, which can exhibit bi-stability at the most, is insufficient. The present work analyzes in this regime corresponding quantum properties by mapping the problem onto a highly-nonlinear quasi-energy operator in a rotating frame. This allows us to identify in detail parameter regions where simplifications such as the Duffing approximation are valid, to explore classical-quantum correspondences, and to study how quantum fluctuations impact the effective junction parameters as well as the dynamics around higher amplitude classical fixed points.

Junction properties of single ZnO nanowires with asymmetrical Pt and Cu contacts

Metal–semiconductor interfaces play a crucial role not only for regulating the electronic conduction mechanism but also in determining new functionalities in nanosized devices. In this work, we reported the investigation of the junction properties of single ZnO nanowires (NWs) asymmetrically contacted by means of a Pt electrochemically inert and a Cu electrochemically active electrode. At low applied voltages, these devices operate as diodes where the conduction mechanism was found to be dominated by the Schottky barrier at the Cu/ZnO interface. Junction parameters such as the Schottky barrier height, the ideality factor and the series resistance have been analyzed according to the thermionic emission theory. Different methods for parameter retrieval from I–V–T measurements are discussed and compared. A potential fluctuation model is considered in order to account for barrier inhomogeneities, revealing the presence of two Gaussian distribution of barrier heights. On the other hand, new device features arise from electrochemical dissolution and migration of Cu ions along the NW when high electric fields are implied. These electrochemical processes are underlaying the resistive switching and memristive behavior observed in single ZnO NWs, as suggested also by direct observation of Cu nanoclusters along the nanostructures after the switching events.

Diode Parameters of Heterojunctions Comprising p-Type Ultrananocrystalline Diamond Films and n-Type Si Substrates.

In the current research, heterojunctions comprising p-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films and n-type Si substrates were formed via pulsed laser deposition. To extract their junction parameters via thermionic emission (TE) theory and Norde model, the measurement of dark current density-voltage curves was carried out under various temperatures ranging from 300 to 60 K. Through TE theory, the ideality factor values at 300 K and 60 K were 2.70 and 8.66, respectively. This justified that a heavy recombination process occurs at the junction interface in addition to another tunneling process at 300 K. The tunneling process is predominant at low temperatures. The barrier height values were 0.78 eV and 0.18 eV at 300 K and 60 K, respectively. The values for series resistance (Rs) calculated via Norde model at 300 K and 60 K were 275.24 Ω and 78.66 kΩ, respectively. The increment of Rs at low temperatures was likely due to the decrease of carrier concentration in the B-doped UNCD/a-C:H films when temperature was decreased.

Current-voltage characteristics of Ag/TiO2/n-InP/Au Schottky barrier diodes

The effect of the TiO2 interfacial layer on rectifying junction parameters of Ag/TiO2/n-InP/Au Schottky diodes has been investigated using current-voltage (I-V) measurements in the temperature range of 120-420 K with steps of 20 K. The barrier height is found to be 0.19 eV and 0.68 eV from current-voltage characteristics at 120 K and 420 K, respectively. At 120 K and 420 K, the ideality factor is found to be 3.52 and 1.01 for the Ag/TiO2/n-InP/Au Schottky barrier diode, respectively. These results are gained by the thermionic emission theory at room temperature. Values of series resistances gained from the Cheung-Cheung method are compared with results gained from a modified Norde method. These experimental results indicate that series resistance decreases with an increase in temperature. The current-voltage (I-V) measurements showed that the diode with the TiO2 interfacial layer gave a double Gaussian property in the examined temperature range. The Richardson constant is also calculated from a modified Richardson plot and is found to be very compatible with the theoretical value. Interface state density is also examined by using I-V characteristics.

Waveguide Slot Array Design With Compensation for Higher Order Mode Coupling Between Inclined Coupling Slots and Neighboring Radiating Slots

Existing design equations do not include higher order coupling effects between inclined coupling slots and longitudinal radiating slots of planar arrays. Several studies have shown that higher order mode coupling in the waveguide junctions causes errors in the excitation of radiating slots, which in turn result in antenna performance degradation. Efforts to compensate for these effects have to date been restricted to trial-and-error or applying full-wave analysis to an existing design and perturbing the slot dimensions to improve the array performance. In this paper, we present an efficient design approach that accounts for the higher order coupling in the waveguide junctions. Compensation is achieved with the addition of closed-form terms in the expression for the active admittance of the radiating slots straddling the coupling slot in each branch. In addition, we propose amendments to the method for calculation of coupling slot dimensions that accounts for phase differences between scattering parameters of coupling junctions. The effectiveness of the proposed procedure is demonstrated by means of two illustrative design examples.

Self-biased current, magnetic interference response, and superconducting vortices in tilted Weyl semimetals with disorder

We have generalized a quasiclassical model for Weyl semimetals with a tilted band in the presence of an externally applied magnetic field. This model is applicable to ballistic, moderately disordered, and samples containing a high density of nonmagnetic impurities. We employ this formalism and show that a self-biased supercurrent, creating a {\phi}0-junction, can flow through a triplet channel in Weyl semimetals. Furthermore, our results demonstrate that multiple supercurrent reversals are accessible through varying junction thickness and parameters characterizing Weyl semimetals. We discuss the influence of different parameters on the Fraunhofer response of charge supercurrent, and how these parameters are capable of shifting the locations of proximity-induced vortices in the triplet channel.

Gamma irradiation effects on Al/n-Si Schottky junction properties

In this paper the gamma irradiation effects on the structural and electrical properties of n-Si and Al/n-Si Schottky junctions are presented up to a cumulative radiation dose of 1500 kGy. The structural studies using XRD and Raman spectroscopic techniques showed no greater degradation in the crystallinity of the n-Si crystals due to the irradiation effects. However, considerable variations in the I–V characteristics of Al/n-Si Schottky junctions and its junction parameters such as Schottky barrier height (ΦB), ideality factor (n) and series resistance (RS) indicates the presence of gamma induced defect states in the interface as well as bulk of the crystal. The surface and interface analysis of the irradiated Al/n-Si Schottky junction revealed modification in the effective work function of Al and presence of different chemical states (AlOxSiOx) in the interface. The contribution of these interface trap states on the band bending properties and I–V characteristics are explained in detail by realizing the power law characteristics and energy band diagram of the Al/n-Si Schottky junction.

Properties of Ferromagnetic Josephson Junctions for Memory Applications

In this work we give a characterization of the RF effect of memory switching on Nb-Al/AlOx-(Nb)-Pd$_{0.99}$Fe$_{0.01}$-Nb Josephson junctions as a function of magnetic field pulse amplitude and duration, alongside with an electrodynamical characterization of such junctions, in comparison with standard Nb-Al/AlOx-Nb tunnel junctions. The use of microwaves to tune the switching parameters of magnetic Josephson junctions is a step in the development of novel addressing schemes aimed at improving the performances of superconducting memories.

Evaluation of Josephson Junction Parameter Dispersion Effects in Arrays of HTS SQUIDs

We report on the experimental evaluation of dispersion effects on superconducting quantum interference device (SQUID) arrays made with high-temperature superconductor technology. The dispersion of Josephson junction parameters not only results in different operational temperature ranges but also in a flux shift of the voltage versus flux response of the SQUID. Another contribution to the phase shift originates from unbalanced inductances of each branch of the SQUID loop. Measurements show that both contributions can be discriminated. Optimal operation of SQUID arrays is obtained in principle only when these self-induced fluxes are negligible. Degradation of the response is more important when the involved currents are larger, i.e., at lower temperature. We compensated these phase shifts for an array of a few SQUIDs connected in series by direct current injection in one of the branches of each SQUID, thereby recovering the characteristic “antipeak” response. This demonstrates that in the lower temperature range of SQUID operation, phase shifts are mainly responsible for the degradation of the SQUID array response.

Indicators of Esophageal pH-Impedance Monitoring and High-Resolution Manometry in Patients with Various Forms of Gastroesophageal Reflux Disease

Aim. The aim of the study is to analyze the regularities of changes in the basic indicators of esophageal pH-impedance monitoring and high-resolution manometry in patients with non-erosive reflux disease (NERD), erosive reflux disease (ERD) and Barrett’s esophagus (BE) in comparison with healthy individuals.Materials and methods. 69 patients were examined, including 19 patients with NERD, 16 patients with ERD, 14 patients with BE and 20 individuals comprising the control group (CG). The gender structure was as follows: 44 male and 25 female patients. The average age of the examined patients was 46 years. All patients underwent 24-hour esophageal pH-impedance monitoring and high resolution manometry.Results. According to the data of 24-hour pH-impedance monitoring, the total time in the esophagus with pH &lt; 4 was 2.4 % in the control group, 9 % in the NERD group, 20.25 % in the ERD group and 23.5 % in the patients with BE (p &lt; 0.05). The average number of acid refluxes was 22.5 in CG, 61 in the NERD group, 77 in the ERD group and 86 in patients with BE (p &lt; 0.05). The time of chemical clearance was 1.7 minutes in CG, 2.2 minutes in the group of patients with NERD, 2.9 minutes in the ERD group and 3 minutes in the BE group (p &lt; 0.05). The mean nocturnal baseline impedance was 2483.5 Ohm in CG, 1775.0 Ohm in the NERD group, 771.0 Ohm in the ERD group and 911.0 Ohm in the BE group (p &lt; 0.05). The normal parameters of the esophagogastric junction (EGJ) structure and function according to the data of highresolution manometry were observed among 85 % of the control group, 63 % of patients with NERD, 25 % of patients with ERD and 36 % of BE group. The presence of hiatal hernia (HH) and/or hypotension of lower esophageal sphincter (LES) was observed in 15 % of patients from the CG, in 37 % of patients with NERD, in 75 % of patients with ERD and in 64 % of patients with BE. The normal parameters of the motor function of the esophagus were observed in CG (85 %), as well as in patients with NERD (79 %). In patients with ERB and BE, normal motor activity was noted in 25 % and 29 % of the cases, respectively. Disturbances of the motor function of the thoracic esophagus in CG were represented in 10 % of the cases by ineffective peristalsis and hypercontractility in the form of distal esophagospasm in 5 % of the cases. In the NERD group, 16 % of patients had ineffective peristalsis and 5 % of patients had hypercontractility in the form of a hypercontractile esophagus. In patients of ERD and BE groups, the disorders of the motor function of the thoracic esophagus were predominantly represented by ineffective peristalsis, in 75 % and 50 % of the patients, respectively. In addition, in the group of patients with BE, in 21 % of the cases, motor function disorders were observed in the form of absence of thoracic esophagus contractions.Conclusion. It is shown that such indicators as increased level of acid exposure, increased amount of acid reflux, slowed chemical clearance, lowered mean nocturnal baseline impedance, as well as disorders in the structure and function of the esophageal-gastric junction and motility of the thoracic esophagus are associated with the severity of GERD.

Josephson ladders as a model system for 1D quantum phase transitions

We propose a novel platform for the study of quantum phase transitions in one dimension (1D QPT). The system consists of a specially designed chain of asymmetric SQUIDs; each SQUID contains several Josephson junctions with one junction shared between the nearest-neighbor SQUIDs.We develop the theoretical description of the low energy part of the spectrum. In particular, we show that the system exhibits the quantum phase transition of Ising type. In the vicinity of the transition the low energy excitations of the system can be described by Majorana fermions. This allow us to compute the matrix elements of the physical perturbations in the low energy sector. In the microwave experiments with this system, we explored the phase boundaries between the ordered and disordered phases and the critical behavior of the system's low-energy modes close to the transition. Due to the flexible chain design and control of the parameters of individual Josephson junctions, future experiments will be able to address the effects of non-integrability and disorder on the 1D QPT.

Implications of electron beam irradiation on Al/n-Si Schottky junction properties

The 7.5 MeV electron beam irradiation (EBI) effects on the Al/n-Si Schottky junction properties is studied in detail by analyzing I-V characteristics, power law characteristics, photoelectron spectra and energy band diagrams. The modifications in the junction parameters such as Schottky barrier height (ΦB), ideality factor (n), and series resistance (RS) at different irradiation doses are caused due to the formation of Al2O3-SiO2 dielectric medium in the interface of Al and n-Si. As a result, ΦB and band bending properties of the junction were modified. A linear correlation of ΦB with EBI dose, interface trap states (m) and effective work functions (EWFs) suggests that the EBI technique is particularly advantageous for the miniature of devices which use band lineup as a key parameter in the device processing.

Effect of disorder on coherent quantum phase slips in Josephson junction chains

We study coherent quantum phase-slips in a Josephson junction chain, including two types of quenched disorder: random spatial modulation of the junction areas and random induced background charges. Usually, the quantum phase-slip amplitude is sensitive to the normal mode structure of superconducting phase oscillations in the ring (Mooij-Sch\"on modes, which are all localized by the area disorder). However, we show that the modes' contribution to the disorder-induced phase-slip action fluctuations is small, and the fluctuations of the action on different junctions are mainly determined by the local junction parameters. We study the statistics of the total QPS amplitude on the chain and show that it can be non-Gaussian for not sufficiently long chains.

Optical and electrical performance of ploypyrrol thin films and its hybrid junction applications

In this work, polypyrrole (PPy) thin films were prepared by the in-situ chemical oxidative polymerization technique. The identification of the prepared films was done by using scanning electron microscopy and X-ray diffraction. The optical characterization of PPy films was achieved to obtain the optical band gaps ( = 1.44 and 2.63 eV) and Urbach energy ( = 402 meV). The capacitance and conductance characteristics as a function of frequency at different biasing voltage show the influence of interface under AC conduction. The principle hybrid junction and photovoltaic parameters were extracted from the dark and illuminated current density-voltage characteristics. The PPy-based junction demonstrated adequate rectification behavior. The high value of ideality factor was interpreted to the interface states and the influence of inhomogeneity at the organic/inorganic interface. The results show that the PPy-based hybrid junction could be utilized as an optical sensor for the optoelectronic application.

ANALYSIS OF POSTOPERATIVE OUTCOMES OF DEGENERATIVE DISEASES OF THE LUMBOSACRAL JUNCTION

ABSTRACT Objective: The article presents an analysis of the clinical efficacy and causes of unsatisfactory outcomes of surgical treatment in patients with degenerative diseases of the lumbosacral junction of the spine. Methods: Patients were allocated to one of three groups, depending on the method of surgical intervention on the lumbosacral junction: 1) (n=352) - operated by the method of microsurgical discectomy; 2) (n=83) - operated with the use of artificial IVD prostheses; 3) (n = 183) - operated with the use of interbody fusion and posterior rigid stabilization. To investigate the causes of unsatisfactory outcomes, a correlation analysis was conducted of long-term clinical outcomes with preoperative instrumental parameters in the operated segment, surgical tactics used, and the development of complications. Results: It is determined that long-term “good” clinical outcomes are associated with individual preoperative parameters of the lumbosacral junction of the spine - linear displacement, sagittal angulation, height of the interbody space, degree of IVD degeneration by ADC. Conclusion: In degenerative diseases of the lumbosacral junction of the spine, the detailed analysis of long-term clinical outcomes enable the identification of the causes that affect the development of unsatisfactory outcomes, which are individual morphostructural changes in the lower lumbar segment: the amplitude of the segmental angle, the angle of the lumbar lordosis, the degree of linear displacement of the vertebrae, the height of the interbody space, and ADC. Complex clinical and instrumental analysis enabled us to determine possible surgical tactics. Level of Evidence II; Prognostic Studies— Investigating the Effect of a Patient Characteristic on the Disease Outcome.

Dependence of the 8-plate position inhemiepiphysiodesis on the X-ray parameters of the epimetaphyseal bone junction

Introduction. To correct axial deformities in children at the knee joint level, the method of “guided growth” using the 8-plate is applied. Despite the widespread use of this method, the toolkit for its implementation was developed mainly for patients with idiopathic deformities and does not take into account the features of the epimetaphyseal bone junction in children with skeletal dysplasias.&#x0D; Aim. To develop X-ray criteria that characterize anatomical features of the epimetaphyseal region of the bone to predict possible difficulties associated with the position of the metal structure in hemiepiphysiodesis.&#x0D; Materials and methods. We developed calculations of the X-ray parameters of the epimetaphyseal junction of the bone (angle of the epimetaphyseal junction and index of the epimetaphyseal junction) in 58 patients (107 lower limbs) with axial deformities in the frontal plane at the knee level in skeletal dysplasias (main group). The control group included 50 children (67 lower limbs) with identical deformities but without a primary lesion of the growth plate in which similar calculations of the X-ray parameters were performed. In stage I of the study, all patients were admitted to the Department of the Turner Research Institute for Children’s Orthopedics for temporary hemiepiphysiodesis using the 8-plate to correct axial deformities of the lower extremities at the knee joint level. In stage 2, the metal structure position was evaluated after the operative treatment that adhered the plate to the bone metaphysis. A total of 255 plates were fixed: the hemiepiphysiodesis of the femur was performed in 138 cases and of the tibia in 117. Pearson correlation coefficient analysis was performed by using IBM SPSS Statistics version 23 software.&#x0D; Results. Among the patients who underwent surgical interventions using the method of guided growth, incomplete adherence of the plate to the bone was observed in 43 (17.3%) of 255 fixed plates because of the anatomical features of the epimetaphyseal region and more often in patients with skeletal dysplasias.&#x0D; Conclusion. We developed X-ray criteria for the angle of the epimetaphyseal junction and the index of the epimetaphyseal junction that are recommended for prediction of the position of metal structures.

Intra- and interobserver variability in the diagnosis of GERD by real-time MRI

The purpose of this study was to assess the reproducibility of functional and anatomical parameters of swallowing events as determined by real-time MRI at 40 ms temporal resolution (25 frames per second). Twenty-three consecutive patients with gastroesophageal reflux disease (GERD) underwent real-time MRI of the gastroesophageal junction at 3.0 T. Real-time MRI was based on highly undersampled radial fast low angle shot (FLASH) acquisitions with iterative image reconstruction by regularized nonlinear inversion (NLINV). MRI movies visualized the esophageal transport of a pineapple juice bolus, its passage through the gastroesophageal junction and functional responses during a Valsalva maneuver. His-angle, sphincter position, sphincter length and sphincter transit time were assessed by two radiologists. Interobserver and intraobserver intraclass correlation coefficients (ICC) were evaluated and Bland-Altman plots were constructed to assess the observer agreement. Interobserver agreement was excellent for sphincter transit time (ICC = 0.92), His-angle (ICC = 0.93), His-angle during Valsalva maneuver (ICC = 0.91) and sphincter-to-diaphragm distance (ICC = 0.98). Sphincter length and oesophageal diameter showed good interobserver agreement (ICC = 0.62 and ICC = 0.70). Intraobserver agreement was good for sphincter length (ICC = 0.80) and excellent for sphincter transit time, His-angle and His-angle during Valsalva maneuver, sphincter-to-diaphragm distance, and esophageal diameter (ICC = 0.91; ICC = 0.97; ICC = 0.97; ICC = 0.998; ICC = 0.93). All functional parameters of the gastroesophageal junction had good to excellent reproducibility. Visual assessment of Bland Altman plots did not reveal any systematic interobserver bias. In conclusion, the visualization of swallowing events by real-time MRI has a high potential for clinical application in gastroesophageal reflux disease.