Point Probe Measurements Research Articles

Complete flow characterization from snapshot PIV, fast probes and physics-informed neural networks

Physics-informed neural networks (PINNs) are function approximators that can incorporate physics laws during training. In recent years, PINNs have been shown to be capable of reconstructing fluid behavior using constraints based on the Navier–Stokes equations and field data. On the downside, the lack of time resolution in a wide range of experimental applications severely limits the applicability of PINNs. We propose a novel methodology based on feeding PINNs with time-resolved fields estimated from non-time-resolved field measurements (e.g. particle image velocimetry) and time-resolved pointprobe measurements (e.g. hot-wires). First, the dimensionality of the problem is reduced by using as a target the temporal modes from a truncated proper orthogonal decomposition (POD) of the velocity fields. Then, using a multilayer perceptron (MLP), a correspondence is established between probe data and the POD time coefficients of the velocity fields. The estimated fields are then fed to the PINN to enhance the data and increase precision. As a further benefit, additional derived quantities not available in the raw data, such as the pressure distribution, can be extracted if suitable boundary conditions are provided. We validate the method on synthetic test cases based on the direct numerical simulation of the wake of a fluidic pinball. Furthermore, we test the algorithm in an experimental case of the wake of a stalled wing. The results show that the PINN is able to reduce the error in the estimated fields, provided that the reference data obtained from the estimation with the MLP are sufficiently accurate.

Influence of Fe3+ ion substitution on Structural, Magnetic Properties and Magnetoresistance Effect of Pr0.75Na0.05K0.20MnO3 System

The effects of partial substitution of Fe at the Mn site on structural, magnetic, and electrical properties of monovalent doped Pr0.75Na0.05K0.20Mn0.95Fe0.05O3 manganite prepared by the solid-state method were investigated. X-ray Diffractometer, AC Susceptibility, and four point probe measurements were used to characterize the structural, magnetic, and electrical properties. The sample crystallized in an orthorhombic structure with a Pnma space group. The sample exhibited ferromagnetic (FM) to paramagnetic (PM) transition behaviour with Curie Temperature, TC value of 121.5 K. From the Resistivity versus temperature analysis, the sample exhibited insulating behaviourover entire temperature from 30 K - 300 K. Fe substitution exhibited high magnetoresistance (MR %) value at low temperature region, indicating the extrinsic mechanism of MR effect.

Probing magnetization dynamics of iron oxide nanoparticles using a point-probe magneto-optical method

Magnetic nanoparticles (MNPs) are promising as local heat generators for magnetic hyperthermia under AC magnetic fields. The heating efficacy of MNPs is determined by the AC hysteresis loop area, which in turn is affected by the dynamic magnetic properties of the nanoparticles. Whilst inductive-based AC magnetometers can measure the average magnetic behavior of samples, the use of the magneto-optical Faraday effect with a focused laser spot allows point-probe measurements to be made, and without some of the magnetic field limitations imposed by inductive methods. In this work, the AC magnetic properties of different sized iron oxide MNPs in suspension were measured by AC magnetometry and AC susceptibility techniques. AC hysteresis loops measured by magneto-optical magnetometry were validated using a commercial inductive AC magnetometer, and compared to the magnetization relaxation behavior revealed by fitting the AC susceptibility data. The spatial sensitivity of the point-probe magneto-optical method is also demonstrated by measuring the AC hysteresis loop from large (>1 μm) MNP aggregates dried onto glass slides. These aggregated particles are found to be magnetically softer than in their suspension form, suggesting interparticle coupling mechanisms could occur when the nanoparticles form dense aggregates.

Variation of ZnS deposition time on chemically prepared Cd1-xZnxS ternary compound from CdS/ZnS bilayers

Chemical bath deposition (CBD) was successfully used for the preparation of cadmium zinc sulphide (Cd1-xZnxS) ternary alloy thin film with × composition, in the range of 0 and 1, from post annealing treatment of bilayer cadmium sulphide (CdS)/zinc sulphide (ZnS) thin film. Increasing the ZnS layer deposition time leads to an increase in the overall thickness of the bilayer with an attendant increase in zinc ion concentration. From the XRD measurement, thin film samples presented hexagonal structure, with a shift in the peaks position to higher angles coupled with a decreasing crystalline size and lattice constants as zinc ion is continuously incorporated into the Cd1−xZnxS thin films. The continuous addition of the wider band gap energy ZnS into the ternary compound as the ZnS deposition time increases constantly brought about the widening of the band gap energy. Energy dispersive spectroscopy (EDS) measurement established the presence of the major elements Cd, Zn and S. The room temperature electrical resistivity determined from the point probe measurement ranges between 2.1 × 10-3 and 1.2 × 101 Ωm, and showed a decrease with increasing zinc ion contents. In this study, it was established that Cd1-xZnxS ternary compounds can be prepared starting with CdS/ZnS bilayer, and its post thermal annealing, with the band gap energy able to be accurately controlled by modifying the CdS/ZnS thickness ratio through variation of ZnS deposition time. The results from CdZnS thin film compounds prepared under this present condition established its superior effectiveness as a buffer layer in thin film solar cells.

Investigation of field free region formed by dual Halbach array for focused magnetic hyperthermia

Abstract One of the challenges with magnetic fluid hyperthermia (MFH) is the limited control of magnetic nanoparticle (MNP) oscillations. To overcome this problem new approaches such as localization of MNP oscillations are being explored. In this study, we investigated the manipulation of field free region form by dual Halbach array displacements. We used finite element method simulation to examine gradient patterns in the workspace. Then, we created an experiment platform and took point probe measurements. As a result of the research, it was found that the field free region form can be manipulated by parametric distance changes of dual Halbach array. According to the findings, the field free region can expand and its shape can change from a point-like form to an ellipse-like surface by varying the distance between the arrays. The mapping of dual Halbach array generated gradient patterns for focused MFH was investigated for the first time in this study.

Megahertz-rate background-oriented schlieren tomography in post-detonation blasts.

The understanding and predictive modeling of explosive blasts require advanced experimental diagnostics that can provide information on local state variables with high spatiotemporal resolution. Current datasets are predominantly based on idealized spherically symmetric explosive charges and point-probe measurements, although practical charges typically involve multidimensional spatial structures and complex shock-flow interactions. This work introduces megahertz-rate background-oriented schlieren tomography to resolve transient, three-dimensional density fields, as found in an explosive blast, without symmetry assumptions. A numerical evaluation is used to quantify the sources of error and optimize the reconstruction parameters for shock fields. Average errors are ∼3% in the synthetic environment, where the accuracy is limited by the deflection sensing algorithm. The approach was experimentally demonstrated on two different commercial blast charges (Mach ∼1.2 and ∼1.7) with both spherical and multi-shock structures. Overpressure measurements were conducted using shock-front tracking to provide a baseline for assessing the reconstructed densities. The experimental reconstructions of the primary blast fronts were within 9% of the expected peak values. The megahertz time resolution and quantitative reconstruction without symmetry assumptions were accomplished using a single high-speed camera and light source, enabling the visualization of multi-shock structures with a relatively simple arrangement. Future developments in illumination, imaging, and analysis to improve the accuracy in extreme environments are discussed.

Water in Sugar Electrolytes and Application to Electrodeposition of Superconducting Rhenium

A systematic electrochemical study is carried out on electrolytes with superhigh concentrations of fructose. The effect of fructose concentration on the viscosity and conductivity of electrolyte are determined and analyzed using Walden rule and the theory of rate process. The diffusion rates of proton and cupric cation are calculated from the peak current in cyclic voltammogram on stationary electrode and the limiting current on rotating electrodes. Raman spectroscopy is used to characterize the hydrogen bond network in water and the effect of fructose concentration on such network. Rhenium deposition with different fructose concentrations is studied on rotating disc electrodes. X-ray fluorescence, X-ray diffraction, and four point probe measurements at cryogenic temperature are used to study the deposition rate, crystallographic structure, and superconductivity of film, respectively.

Investigation of CZTS absorber layer deposited by spin coating technique for photovoltaic applications

In this work we prepared and deposited Cu2ZnSnS4 (CZTS) absorber layers by sol gel spin coating technique on ordinary glass substrates. We studied the influence of annealing time on structural, compositional, morphological, optical and electrical properties of films at different times of 5, 10 and 20 min, respectively. The films have been analyzed by different characterization techniques such as X-ray diffractometer (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), UV–visible-NIR spectrophotometer and four point probe method. XRD patterns showed pure kesterite CZTS with preferential orientation along (112) plane and calculated lattice parameters a = b = 0.5428 nm and c = 1.0849 nm. Raman scattering measurements confirmed the existence of a single CZTS phase showing a single peak at 338 cm−1. SEM images showed compact, uniform and densely surface morphology. EDS analysis indicated near-stoichiometric CZTS films, UV–Visible-NIR spectrophotometer showed that the optical band gap energy of CZTS thin films is found to be between 1.48 and 1.7 eV. Four point probe measurements exhibited a suitable electrical conductivity in the range 3.03–3.44 (Ω.cm)−1. These properties make the as-synthesized CZTS films an appropriate material as absorber layer in solar cells applications.

Electrical Properties Engineering of Sputtered Indium Gallium Zinc Oxide Semiconductor Thin Films

The influence of deposition conditions and laser annealing on the electrical properties of indium gallium zinc oxide (IGZO) semiconducting thin films was investigated. 50 nm thick IGZO films were deposited by radio frequency (RF) magnetron sputtering at room temperature and subsequently laser annealed in ambient conditions to enhance the IGZO electrical properties. Excimer laser annealing (ELA) was conducted by Krypton fluoride (KrF) excimer laser (λ= 248 nm) with single pulse over a range of fluences up to 175 mJ/cm2. The electrical properties of IGZO films were studied by four point probe (4PP) and Hall Effect measurements. Results demonstrated that the applied deposition conditions control the IGZO films metallic composition, which is found to be directly linked to IGZO films electrical properties. The as-deposited IGZO films were highly resistive with sheet resistance > 5 MΩ/sq and therefore 4PP and Hall Effect measurements could not be performed on the as-deposited films. Upon ELA, however, the sheet resistance is noticeably reduced to about 500 ± 10 % Ω/sq. Also, IGZO films demonstrated Hall mobility of 14 cm2/Vs and electron density of 3×1019/cm3 subsequent to ELA at 100 mJ/cm2. The reported findings present ELA as an efficient technique to engineer the electrical properties of sputter-deposited IGZO films. Therefore, a combination of room temperature deposition, via RF magnetron sputtering, and laser annealing could be used as a fabrication route of IGZO films for active layers of transparent thin film transistors (TTFTs) and applicable to flexible electronics which require low substrate temperature.

Metal-Molecule-Metal Junctions on Self-Assembled Monolayers Made with Selective Electroless Deposition.

Electronic transport through molecular-scale devices has been studied extensively for its extraordinary dimension superiority. Assembling such devices into large-scale functional circuits is crucial since the molecular tunnel junctions must be reliable, stable and reproducible during technological applications. In ideal circumstances, the device architecture should be designed such that the metal-molecule-metal (MMM) junctions can be analyzed by the more sensitive four point probe system. In this paper, we expound a delicate method to manufacture molecular junctions, which show excellent stability and reproducibility with high yields (>91 per cent). We form self-assembled monolayers (SAMs) on conductive Au thin film by microcontact printing and then generate robust covalently bound metal thin film electrodes on top of the SAMs by selective electroless deposition. Following MMM junction formation, a photoresist is coated and wells are opened on each feature by lithography. Then, Au thin film, as a permanent top electrode, is deposited into the photolithographically defined well. Conductivity analyzations were carried out on the 50 μm square junctions by the four point probe measurement, and the results showed reproducible tunneling I-V characteristics. This method reveals an approach not only offering a unique vehicle to investigate the electrical properties of molecule ensembles in MMMs, but also making a significant step toward MMM applications at the device level.

The Liquid Phase Deposition of ZnPtBNs: Study on Structural, Morphology, and Their Sheet-Resistant

This paper reports ZnPt bimetallic nanoparticles (ZnPtBNs) synthesis through the liquid phase deposition (LPD) of of Zn(NO3)2.6H2O onto the indium-titanium oxide (ITO) substrates at various concentrations. The Effects of growth solution, the morphology, structural, and sheet resistance were studied. After preparation, the materials were characterized by using field emission electron microscopy (FESEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Four Point Probe (FPP) measurement by using Keithley 2401 source-meter. By inserting a growth solution into the ITO substrate the ZnPtBNs was successfully in-situ prepared. The synthesized ZnPtBNs exhibited homogeneous, fibrous at the (111) orientation with an average diameter of 100-700 nm. The atomic ratio of Zn:Pt and sheet resistance of ZnPtBNs decreased with the increase of Zn(NO3)2.6H2O concentration. The optimal elemental composition of the sample was at a ratio of Zn:Pt (1:25) obtained at 0.467 mM of Zn(NO3)2.6H2O. It showed the smallest sheet resistance (13.41 ?) which was 38% lower than the ITO sheet resistance (18.44 ?).

Analysis of field free region formed by parametric positioning of a magnet pair for targeted magnetic hyperthermia

One of the challenges that arise in the practical applications of magnetic fluid hyperthermia (MFH) is the limited control of magnetic nanoparticle oscillations. In this study, we investigated to manipulate field free region (FFR) form and location by symmetric and asymmetric displacements of a magnet pair (MP). Finite element method (FEM) simulation was used to predict gradient patterns (GPs) in the workspace. An experiment platform was produced and point probe measurements are taken. It is observed that FFR form and position can be manipulated with parametric distance and angle changes. FFR can shrink and its form can be transformed to the linelike or point-like areas. Focus of FFR can be moved off-center, and it can be directed to different parts of the target object. The mapping of GP produced by a MP for the use of targeted MFH is discussed for the first time in this study. And the findings provide insight into which GP is appropriate in which situations in targeted MFH.

Synthesis of Conducting Polyaniline with Photopolymerization Method and Characterization

Polymers as they are known as molecules formed by repetition of small molecules known as monomers, polymers that are often used cannot conduct electricity. Along with the development of the polymer era at this time can also conduct electricity known as conductive polymers. One of the conductive polymers that attracts attention is polyaniline. Synthesis of polyaniline conductive polymers is carried out with aniline monomers mixed with Ethylene Glycol Dimetacrylate (EGDMA) as Crosslinkers, and Dimethoxy phenylacetophenone (DMPP) as the initiator. In this reasearch, the polymerization processed with the photopolymerization method with a mixture of Aniline (mL), DMPP (0.1 g), and EGDMA (mL) polymerized with photopolymer. The polymers obtained were tested for electrical conductivity, the composition which showed optimum conductivity was in the ratio of aniline and EGDMA 1 : 1 with the electrical conductivity of 0.001462 Ohm.cm−1. The conductivity measurement is done by using Four Point Probe (FPP) and other characterization measurements using FTIR (Fourier Transform Infrared) and TGA (Thermo-gravimetric Analysis).

Tailoring optical and electrical properties of ternary Pb1−xCoxS thin films synthesized from a combination of two complexing agents

Chemical bath deposition technique was used to synthesized Pb1−xCoxS compounds at a bath temperature of 75 °C by using double complexing agents. The thin films were characterized by varies of techniques. The XRD study confirmed that all the prepared thin films had face-center cubic crystal structure and the crystalline oriented along the (111) plane irrespective of cobalt concentrations. The XRD results further revealed that cobalt incorporation had a considerable effect on the intensity and position of the diffraction peaks. The SEM and HRTEM analyses justified that the surface morphology of Pb1−xCoxS thin films was strongly dependent on the amount of the dopant. The presence of Co, S and Pb elements in the prepared compounds was established by the EDX analyses. The UV–Vis study demonstrated that the band gap values of Pb1−xCoxS films engineered from 0.80 to 1.50 eV by varying cobalt doping concentrations. Furthermore, the refractive index, dielectric constant and linear optical susceptibility were calculated using the energy band gap values. The dc-two point probe measurement verified that the electrical properties of the Pb1−xCoxS thin films were considerably changed by the cobalt doping concentrations and the thermal activation energies were found in the range of 0.587–0.976 eV.

Effect of compositional ratio of Sn in SnZn thin films on morphological and chemical properties

Zinc (Zn) and tin (Sn) based alloy thin films have been of recent interest in the semiconductor industry. Despite such interest, knowledge on how the concentration of Sn affects the chemical, electrical, optical and surface properties SnZn thin films is still scarce. In this paper, SnZn thin films with varying ratios of Zn to Sn were fabricated through radio frequency (rf) magnetron sputtering. The resulting SnZn thin films were analyzed using scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), contact angle measurements, a 4-point probe, X-ray diffraction (XRD) patterns, and ultraviolet photoelectron spectroscopy (UPS). According to our results, The SnZn thin films that were fabricated using an rf power of 15 W to the Sn target had the roughest surface morphology and the films fabricated using an rf power of 10 W to the Sn target had the largest grain size. Contact angle measurements and 4 point probe measurements revealed that the SnZn were overall hydrophobic and the electrical conductivity increased with doping higher concentrations of Sn. XRD showed that SnZn thin films had larger grain sizes than pure Zn thin films. XPS and UPS analysis suggested the Fermi level was brought closer to the vacuum level when Sn was doped in Zn thin films.

In vacuostudies on plasma-enhanced atomic layer deposition of cobalt thin films

Plasma-enhanced atomic layer deposition (PE-ALD) of cobalt (Co) using cyclopentadienylcobalt dicarbonyl [CpCo(CO)2] combined with hydrogen, nitrogen, ammonia, and argon based plasma gases was investigated. The utilized ALD tool was clustered to an ultrahigh vacuum analytic system for direct surface analyses including X-ray photoelectron spectroscopy (XPS). The combination with a nondestructive surface analysis system enabled a sample transfer without vacuum break and thereby a direct qualification and quantification of the chemical surface composition under quasi in situ conditions. The authors studied the influence of process parameters (e.g., pulse times, plasma power, and substrate temperature) on film compositions and film properties. The occurrence and prevention of sputtering effects due to ion bombardment at high plasma powers were discussed. Beyond those results, precise information about the impact of different plasma gas compositions on the resulting film properties was obtained. Cobalt films grown using a hydrogen/nitrogen (H2/N2) plasma as a coreactant showed a stable film composition (CoNx) with a high Co content of 75 at. %. Using scanning electron microscopy and four point probe measurements, a moderate electrical resistivity of about 56 μΩ cm was calculated for a 20 nm film. The high sensitivity of in vacuo XPS measurements allowed investigations of interface reactions for a single PE-ALD pulse as well as investigations of the initial film growth mechanisms. The nucleation of CoNx films during PE-ALD using H2/N2 plasma as a coreactant was investigated on several substrate materials by XPS. After the very first cycle of the PE-ALD process, no Co could be detected on all the investigated substrates. XPS revealed that the plasma pulse was needed to provide active binding sites for the adsorption reaction of precursor molecules due to the formation of Si-Nx or Si-NxOy surfaces. Therefore, the plasma pulse plays an important role in the PE-ALD process of Co on silicon surfaces. The early cycles were characterized by the onset of Co—O bonds. The homogeneous film body on all substrates consisted of Co-nitride compounds.

Automatic Micro-Robotic Identification and Electrical Characterization of Graphene.

Micromechanically exfoliating graphene on / substrates is commonplace for graphene researchers, but locating actual graphene flakes on these substrates is a high-effort and tiresome task. The main purpose of this work was to establish a completely automated procedure to identify those graphene flakes with as little human interaction as possible, improving on the limitations of current methods. Furthermore, automatic electrical characterization of the identified flakes was performed. The proposed micro-robotic automation sequence consists of three main steps. To start, a sample surface plane is calculated, based on multiple foci points across the substrate. Secondly, flakes on the substrate are identified in the hue, saturation, and value (HSV) color space, with an implementation to fit the measurement probe, used to avoid undersized samples and adjust the flake orientation. Finally, electrical characterization is performed based on four point probe measurements with the Van der Pauw method. Results of the successfully implemented automation sequence are presented together with flake electrical properties and validation.

Dry and Wet Ball Mill Syntheses of Sb2Se3 from Its Constituent Elements

Binary antimony selenide (Sb2Se3) compound was synthesized by the mechanical alloying of constituent elements. Both dry and wet mill syntheses methods were applied. Dry milling was done in Ar atmosphere. Wet milling was done using toluene and n-butyl alcohol as a process control agent (PCA). It was found that Sb2Se3 phase was formed using toluene as PCA, whereas usage of n-butyl alcohol led to the formation of mixed phases consisting of Sb2Se3 and unreacted antimony and selenium. Single phase Sb2Se3 was obtained in 6 h and 13 h, respectively, through dry and wet milling, which was confirmed by x-ray diffraction (XRD) and Raman spectroscopy studies. Diffused reflectance spectroscopy studies of as-milled Sb2Se3 yielded direct band gap values of 1.10 eV and 1.18 eV for dry and wet milled samples, respectively. Particle-induced x-ray emission studies revealed that there is no impurity present in the compound and confirmed near stoichiometry. High-resolution transmission electron microscopy observations showed d spacing values of 0.28 nm for dry and toluene milled samples that corresponds to the (221) plane. The milled Sb2Se3 was used as source material and thin films were grown using the e-beam evaporation method. The as-grown films were characterized using XRD, Raman spectroscopy that showed a single phase nature of the films and optical transmission spectra analysis yielding a band gap of 1.29 eV. Electrical resistivity of the films was measured using a two probe method showing a resistivity of 1.6 × 107 Ω cm. Hot point probe measurement indicated that the as-grown Sb2Se3 films are p-type in nature.

The heterostructure and electrical properties of Sb2Se3/Bi2Se3 grown by molecular beam epitaxy

We report the growth and characterization of Sb2Se3/Bi2Se3 bilayer films fabricated by molecular beam epitaxy. High quality heterostructures are obtained as evidenced from the X-ray diffraction (XRD), atomic force microscopy and high-resolution transmission electron microscopic (HRTEM) analysis. Interestingly, Sb2Se3 grows as a (120) hexacrystal film in orthorhombic phase on rhombohedral Bi2Se3 (0001) plane, as verified by the out-of-plane and in-plane XRD scans. The cross-sectional TEM studies indicate a sharp interface between Sb2Se3 and Bi2Se3, which is important for the protection of surface states Bi2Se3. The ultraviolet photoelectron spectroscopy indicates that the Fermi level located 0.95 eV above the valence band maximum in Sb2Se3. The insulating nature of Sb2Se3 is confirmed by the nonlinear current-voltage curve via the vertical junction electrical measurement. By four point probe measurements, we confirm the charge transfer effect from Sb2Se3 into Bi2Se3, and such effect can be reduced in the Sb2Se3/(Bi0.7Sb0.3)2Se3 bilayer. This work opens a new avenue for the synthesis of multilayers consisting of topological insulators and ordinary insulator, which is important for harvesting of the multiple surface states for advanced electronic and spintronic applications.

Effect of annealing time on the structural and optical properties of n-CuO thin films deposited by sol-gel spin coating technique and its application in n-CuO/p-Si heterojunction diode

This paper reports the growth of n-type CuO (copper II oxide) thin film with improved crystallinity on p-Si substrate using sol-gel spin coating process. The electrical conductivity of the deposited film was determined as n-type using Hot point probe measurement. Further, an in-depth analysis of the annealing time effect on the deposited thin film was done to observe its structural and optical properties. The structural characterization of the deposited film was done with the help of X-ray diffraction and Field Emission Scanning electron microscope. The optical parameters, such as reflectance, refractive index were determined in the spectral range of 300 nm - 800 nm with the help of ellipsometry. The effects of annealing time on band gap, extinction coefficient, dielectric constant for the annealed films were also extracted to observe its application for optoelectronic devices. Further, using the film annealed for 15 mins. n-CuO/p-Si hetero-junction diode was fabricated and characterized. The experimentally obtained electrical parameters of the fabricated n-CuO/p-Si hetero-junction diode were also validated by the results of numerical simulation data obtained by usinga commercially available device simulator. The developed hetero-junction was investigated by considering a conventional thermionic model. It showed high rectification ratio equal to 6805 and a barrier height equal to 0.81 eV.