Potential Difference Distribution Research Articles

Impact of Spatial Scale and Building Exposure Distribution on Earthquake Insurance Rates: A Case Study in Tangshan, China

In order to examine the effect of spatial scale and building exposure distribution on the pure rate of earthquake catastrophe insurance, this study described three modules for rate determination, put forward the general assumptions and principles for calculating the pure insurance rate, and introduced three types of building distribution and their calculation. Taking Tangshan City of Hebei Province in China as an example, we analyzed the pure rate of regional earthquake insurance in terms of spatial scale and building exposure distribution by using the method of control variables. The results show that for districts (or counties) with large differences in seismic risk, the risk areas can be further divided to apply differential rates. In areas with a diverse distribution of potential earthquake source areas and large differences in building density, there is a risk of overestimating or underestimating the pure rate of earthquake insurance when buildings are distributed evenly or partially evenly. This violates the break-even principle of rate setting. This study also provides a reference for earthquake catastrophe insurance companies to choose the spatial scale and the detailed level of exposure distribution in rate determination.

A study on evaluation method of local pipe wall thinning based on DC potential difference measurement

In this study, a simple method to evaluate the local pipe wall thinning by using the DC potential difference method was examined. The pipe has outer diameter D and thickness t0. The local inner-wall thinning is modeled as a back wall slot having arc-shape cross section of width 2w and depth b. The constant DC current is applied to the pipe through two probes, and the distribution of potential difference between current input and output probes is measured. The potential differences measured before and after thinning are represented as V0 and V1, respectively. The thinning depth b/t0 is evaluated from the maximum value of V1/V0. Three-dimensional finite element method was used to analyze the relation between thinning size and potential difference for various cases. As a result, it was shown that the relation between b/t0 and V1/V0 is affected by w/D. The calibration equation between b/t0 and V1/V0 was obtained by approximating FEM results, and its validity was shown by numerical experiments.

Multi-Channel Exploration of O Adatom on TiO2(110) Surface by Scanning Probe Microscopy.

We studied the O2 dissociated state under the different O2 exposed temperatures with atomic resolution by scanning probe microscopy (SPM) and imaged the O adatom by simultaneous atomic force microscopy (AFM)/scanning tunneling microscopy (STM). The effect of AFM operation mode on O adatom contrast was investigated, and the interaction of O adatom and the subsurface defect was observed by AFM/STM. Multi-channel exploration was performed to investigate the charge transfer between the adsorbed O and the TiO2(110) by obtaining the frequency shift, tunneling current and local contact potential difference at an atomic scale. The tunneling current image showed the difference of the tunneling possibility on the single O adatom and paired O adatoms, and the local contact potential difference distribution of the O-TiO2(110) surface institutively revealed the charge transfer from TiO2(110) surface to O adatom. The experimental results are expected to be helpful in investigating surface/interface properties by SPM.

Analysis of the change of direct current potential difference and diameter distribution of thin pure titanium wire subjected to tensile and fatigue loads for fracture prediction

Analysis of the change of direct current potential difference and diameter distribution of thin pure titanium wire subjected to tensile and fatigue loads for fracture prediction

Analysis of Relationship between Potential Difference and Fiber Distribution inside CFRP Focusing on the Current Path

Analysis of Relationship between Potential Difference and Fiber Distribution inside CFRP Focusing on the Current Path

Temperature-Dependent Local Electrical Properties of Organic-Inorganic Halide Perovskites: In Situ KPFM and c-AFM Investigation.

Organic-inorganic halide perovskite materials are emerging as a new class of photoelectric materials for its low cost, easy preparation, and, especially, outstanding optoelectronic properties. Although tremendous efforts have been made on the regulation and optimization of perovskite materials and their microscopic electrical properties for high-efficiency solar cells, few reports focus on the evolution of electrical properties with temperature changes, especially at the microscopic scale, which will directly affect the device performances at varying temperatures. Here, we map the contact potential difference and photocurrent distribution of MAPbI3 at different temperatures in situ by Kelvin probe force microscopy and conductive atomic force microscopy, emphasizing the different influences of variable temperature and phase transition on the photoelectric properties of grains and grain boundaries (GBs). It is discovered that both the Fermi level and photocurrent decrease as the sample is heated from 30 to 80 °C gradually because of the variation of effective carrier concentration and the degradation of carrier mobility implicated by lattice vibration scattering. The difference between the Fermi level at GBs and that on the grains ascends first and then descends, peaking at 50 °C, near which MAPbI3 transforms from a tetragonal phase to a cubic phase. This peak is speculated as a comprehensive consequence of the increasing difference of the Fermi level of semiconductors with different doping concentrations and the converging properties of grains and GBs with the temperature rising because the lower ion activation energy of the cubic phase at higher temperatures facilitates greatly the ions' movement between grains and GB. The variation trend of the difference of the photocurrent is the same. These findings advance the knowledge on the temperature-induced variations of microscopic photoelectrical properties of organic-inorganic hybrid perovskite materials, which may guide the development of strategies for improving their thermal stability.

The Role of Hydrogen from ALD‐Al2O3 in Kesterite Cu2ZnSnS4 Solar Cells: Grain Surface Passivation

AbstractIn this research, a new route of surface passivation is reported by introducing hydrogen from the atomic layer deposited (ALD) Al2O3 layer into pure sulfide Cu2ZnSnS4 (CZTS) solar cells. Different amounts of hydrogen are incorporated into the Cu2ZnSnS4/CdS interface through controlling the thickness of the ALD‐Al2O3 layer. The device with three cycles of ALD‐Al2O3 yields the highest efficiency of 8.08% (without antireflection coating) with improved open‐circuit voltage of up to 70 mV. With closer examination on the passivation route of ALD‐Al2O3, it is revealed by the surface chemisty study that the Al2O3 can be etched away by ammonium hydroxide in the CdS buffer deposition process. Instead, the hydrogen is detected within a shallow depth from the CZTS surface, and makes a significant difference in the measured distribution of contact potential difference and device performance. This may be interpreted by the effect of hydrogen passivation of the CZTS surface by curing dangling bonds at the surface of CZTS grains. This work may provide a new direction of further improving the performance of kesterite solar cells.

In situ Investigations of Near Phase Boundary Water Diffusion of Ageing Adhesive Bonds by Scanning Kelvin Probe

Many industries nowadays rely on the adhesive bonding technology for their success, most notably aerospace, automotive, construction, and the electronics industry. One of the main advantages of the adhesives is the ability to bond dissimilar materials and the more efficient load transfer in comparison to other joining methods. Several industrial applications request the adhesive joint to withstand loads under different environmental conditions such as high moisture, and extreme temperatures. Thus, predicting the lifetime of adhesively bonded joints under moist environments is crucial to support tailoring the properties for the respective application demand. Relevant effects of water in adhesively bonded components may be strength degradation and introduction of stresses. Knowing the behaviour of the water in adhesive joints may contribute to directing the design of bonded components, lead to greater confidence and increase the use of adhesives in the industry. A significant cause of joint weakening is the effect of water in the interface between adhesive and substrates. There is evidence that the transport kinetics of water in the adhesive bulk do not correspond to the kinetics in the adhesive joint, studies show that water can be absorbed much faster by the interface than by the bulk. [1, 2] The study of the kinetics of water absorption in the interface is a particular challenge, and is also gravimetrically hardly detectable. A powerful and established method which can detect directly the corrosion induced delamination of polymer coatings is the scanning Kelvin probe (SKP). [3] In the present work the SKP is used to study the water uptake of adhesive bonds. To determine the water uptake processes of an adhesive joint by means of SKP, an adhesive is applied to a metal surface, and as second substrate a very thin non-conductive barrier layer is used. Several scanning Kelvin probe experiments are carried out, under different environmental conditions, to define which are the most suitable adhesives, substrates and barrier layers to investigate the water diffusion in situ and near the interface of an adhesive joint. The potential difference distribution is measured time-dependent in order to obtain information about the water absorption kinetics. The tests are accompanied by analytical and electrochemical methods, e.g., dynamic vapour sorption and electrochemical impedance spectroscopy. [1] Zanni-Deffarges, M. P.; Shanahan, M.E.R. (1995): Diffusion of water into an epoxy adhesive. Comparison between bulk behaviour and adhesive joints. In International Journal of Adhesion and Adhesives 15 (3), pp. 137–142. DOI: 10.1016/0143-7496(95)91624-F. [2] Wapner, K.; Grundmeier, G. (2004): Spatially resolved measurements of the diffusion of water in a model adhesive/silicon lap joint using FTIR-transmission-microscopy. In International Journal of Adhesion and Adhesives 24 (3), pp. 193–200. DOI: 10.1016/j.ijadhadh.2003.09.008. [3] Hausbrand, R.; Stratmann, M.; Rohwerder, M. (2009): Corrosion of zinc–magnesium coatings. Mechanism of paint delamination. In Corrosion Science 51 (9), pp. 2107–2114. DOI: 10.1016/j.corsci.2009.05.042.

ANALYSIS OF SURFACE DEFECTS OF ALUMINUM AND ITS ALLOYS WITH A SCANNING KELVIN PROBE

Currently, the use of probe electrometry in non-destructive testing is constrained by the complexity of measurement results interpretation. An output signal of electrometric probe depends on a number of physical and chemical parameters of surface including chemical composition variations, stresses, dislocations, crystallographic orientation of a surface, etc. The study aims to the use of probe electrometry methods for nondestructive testing and analysis of precision metal surfaces’ defects after different treatment or processing. Control of surface defects of aluminum and its alloys was performed with a scanning Kelvin probe technique. The results of scanning were plotted in a form of contact potential difference (CPD) distribution map. Additionally, a histogram of CPD values distribution and statistical characteristics including the expectation of CPD mean value and histogram half-width were calculated either for the whole distribution or for each individual mode in a case of multimodal distribution. The spatial CPD distribution of A99 aluminum and AMG-2 alloy surfaces after electrochemical polishing and diamond finishing was studied. An additional study was held for AMG-2 surface after the formation of 30 microns thick specific nanostructured alumina oxide surface layer. Higher quality surfaces have characterized as more homogeneous distribution of the physical properties (at half-width distribution histogram). Surfaces with higher mechanical strength and overall better mechanical properties found to have lower CPD values that correspond to higher electron work function and surface energy. The presence of the second mode in the CPD distribution histogram indicates the significant proportion of defect areas on the sample surface. Analysis of visualized CPD distribution maps using defined criteria allows detecting and characterizing such defects as residual stress areas, areas with reduced microhardness, surface contamination spots, corrosion defects. This provides the possibility of rapid nondestructive testing and diagnostic of precision metal surfaces, in particular the starting substrates for sensitive elements and sensory devices manufacture.

The composition, structure and surface properties of the titanium-carbon coatings prepared by PVD technique

Amorphous carbon (a-C) and titanium-carbon nanocomposite TiCx/a-C coatings were deposited using the PVD technique. TiCx/a-C were deposited by simultaneous sputtering of graphite and titanium targets using arc pulse (at the frequency of 3 to 25Hz) and arc sputtering respectively. The composition, chemical structure and electrical properties of the surface have been studied by energy-dispersive X-ray spectroscopy, Raman spectroscopy and Kelvin probe force microscopy (KPFM). The increase in graphite sputtering arc pulse frequency is accompanied by the growth of carbon content in TiCx/a-C from 38 to 82at.% and by the change of phase composition. The incorporation of the Ti+ ions into the plasma flow of C+ increases the number of sp2 bonds in carbon matrix of TiCx/a-C, as compared to a-C deposited at the same frequency. The maps of contact potential difference (CPD) distribution over the surface of a-C and TiCx/a-C obtained by KPFM were used to calculate the root-mean-square (RMS) values of CPD. In a-C RMS of CPD decreases with scale up of arc pulse frequency. In TiCx/a-C RMS of CPD nonlinear depends on the carbon content and reaches maximum at CC=44at.%. It has been suggested, that at the contacts of different phases an interface thin layer is formed. The electronic properties of this layer differ from the electronic properties of the bulk phases of nanocomposite. The increase in volume fraction of interface component leads to the drop of RMS of CPD.

Physical Study by Surface Characterizations of Sarin Sensor on the Basis of Chemically Functionalized Silicon Nanoribbon Field Effect Transistor

Surface characterizations of an organophosphorus (OP) gas detector based on chemically functionalized silicon nanoribbon field-effect transistor (SiNR-FET) were performed by Kelvin Probe Force Microscopy (KPFM) and ToF-SIMS, and correlated with changes in the current-voltage characteristics of the devices. KPFM measurements on FETs allow (i) to investigate the contact potential difference (CPD) distribution of the polarized device as function of the gate voltage and the exposure to OP traces and, (ii) to analyze the CPD hysteresis associated to the presence of mobile ions on the surface. The CPD measured by KPFM on the silicon nanoribbon was corrected due to side capacitance effects in order to determine the real quantitative surface potential. Comparison with macroscopic Kelvin probe (KP) experiments on larger surfaces was carried out. These two approaches were quantitatively consistent. An important increase of the CPD values (between + 399 mV and + 302 mV) was observed after the OP sensor grafting, corresponding to a decrease of the work function, and a weaker variation after exposure to OP (between - 14 mV and - 61 mV) was measured. Molecular imaging by ToF-SIMS revealed OP presence after SiNR-FET exposure. The OP molecules were essentially localized on the Si-NR confirming effectiveness and selectivity of the OP sensor. A prototype was exposed to Sarin vapors and succeeded in the detection of low vapor concentrations (40 ppm).

Evaluation of semi-ellipsoidal wall thinning on back surface of plate by direct-current potential difference method

Purpose – Local wall thinning is one of serious problems in aged power generating plants. As the thinning grows inside the pipes, it is difficult to detect and evaluate it from the outer surface of pipe. The purpose of this paper is to evaluate the method of semi-ellipsoidal wall thinning geometry on the back surface of flat plate by direct-current potential difference method (DC-PDM) was proposed as a preliminary research for the pipe wall thinning evaluation. The evaluation was performed for the potential difference numerically obtained by finite element method and the results were discussed. Design/methodology/approach – A number of electric field analyses are necessary to evaluate the geometry of local wall thinning. In this study, defect-current modification method (DCMM), which is very fast analysis method based on the formulated solution for the similar thinning geometry, was used. The DCMM enabled the repeated electric field analyses necessary for the evaluation. Findings – The potential difference on the front surface of plate was higher than the other part because of the electric current disturbance by a wall thinning on the back surface. In addition, the distribution depended on the geometry of the wall thinning. In this study, the shape of the thinning was assumed to be ellipsoid, and the width, depth, and length of the thinning were successfully evaluated based on the potential difference distribution on the front surface. Originality/value – Evaluation of local wall thinning geometry was carried out by repeated analyses using DCMM, and the results were successful. This fact suggests that the evaluation of local wall thinning is possible by DC-PDM. The proposed method is going to be extended to the local wall thinning on the inner surface of pipe by geometrical conversion.

Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition**supported by the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices (University of Electronic Science and Technology of China) (No. KFJJ201313)

Boron-doped nanocrystalline diamond (NCD) exhibits extraordinary mechanical properties and chemical stability, making it highly suitable for biomedical applications. For implant materials, the impact of boron-doped NCD films on the character of cell growth (i.e., adhesion, proliferation) is very important. Boron-doped NCD films with resistivity of 10−2 Ω·cm were grown on Si substrates by the microwave plasma chemical vapor deposition (MPCVD) process with H2 bubbled B2O3. The crystal structure, diamond character, surface morphology, and surface roughness of the boron-doped NCD films were analyzed using different characterization methods, such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope (SKFM). The cytotoxicity of films was studied by in vitro tests, including fluorescence microscopy, SEM and MTT assay. Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates. MG-63 cells adhered well and exhibited a significant growth on the surface of films, suggesting that the boron-doped NCD films were non-toxic to cells.

Cortical Silent Period Reveals Differences Between Adductor Spasmodic Dysphonia and Muscle Tension Dysphonia

Background. The pathophysiology of adductor spasmodic dysphonia (AdSD), like other focal dystonias, is largely unknown. Objective. The purposes of this study were to determine (a) cortical excitability differences between AdSD, muscle tension dysphonia (MTD), and healthy controls; (b) distribution of potential differences in cranial or skeletal muscle; and (c) if cortical excitability measures assist in the differential diagnosis of AdSD and MTD. Methods. Ten participants with adductor spasmodic dysphonia, 8 with muscle tension dysphonia, and 10 healthy controls received single and paired pulse transcranial magnetic stimulation (TMS) to the primary motor cortex contralateral to tested muscles, first dorsal interosseus (FDI), and masseter. We tested the hypothesis that cortical excitability measures in AdSD would be significantly different from those in MTD and healthy controls. In addition, we hypothesized that there would be a correlation between cortical excitability measures and clinical voice severity in AdSD. Results. Cortical silent period duration in masseter and FDI was significantly shorter in AdSD than MTD and healthy controls. Other measures failed to demonstrate differences. Conclusion. There are differences in cortical excitability between AdSD, MTD, and healthy controls. These differences in the cortical measure of both the FDI and masseter muscles in AdSD suggest widespread dysfunction of the GABAB mechanism may be a pathophysiologic feature of AdSD, similar to other forms of focal dystonia. Further exploration of the use of TMS to assist in the differential diagnosis of AdSD and MTD is warranted.

Characteristics of a silicon nanowires/PEDOT:PSS heterojunction and its effect on the solar cell performance.

The interfacial energy-level alignment of a silicon nanowires (SiNWs)/PEDOT:PSS heterojunction is investigated using Kelvin probe force microscopy. The potential difference and electrical distribution in the junction are systematically revealed. When the PEDOT:PSS layer is covered at the bottom of the SiNW array, an abrupt junction is formed at the interface whose characteristics are mainly determined by the uniformly doped Si bulk. When the PEDOT:PSS layer is covered on the top, a hyperabrupt junction localized at the top of the SiNWs forms, and this characteristic depends on the surface properties of the SiNWs. Because the calculation shows that the absorption of light from the SiNWs and the Si bulk are equally important, the bottom-coverage structure leads to better position matching between the depletion and absorption area and therefore shows better photovoltaic performance. The dependence of JSC and VOC on the junction characteristic is discussed.

110 直流電位差分布に基づく平板背面に存在する局部減肉の位置と寸法の推定(材料力学II)

110 直流電位差分布に基づく平板背面に存在する局部減肉の位置と寸法の推定(材料力学II)

Measurement of contact potential difference and material distribution by using an SEFM

Measurement of contact potential difference and material distribution by using an SEFM

Contact Potential Difference Measurement of Adhesion Process during Micro/Meso-scale Injection Upsetting

In micro/meso (between macro and micro)-scale metal forming, the contribution of friction between the material and tool on the material deformation is higher than that in macro-scale metal forming. The friction during forming strongly depends on the adhesion process. The process was studied by measuring the contact potential difference distribution of the tool surface after an injection upsetting stroke. The effect of the annealing temperature of materials and the forming speed on the amount of adhesion was quantified by the measurements.

B010 Measurement of contact potential difference and material distribution by using an SEFM

This paper presents a novel method for the measurement of the contact potential difference (CPD) and material distribution over the sample surface using scanning electrostatic force microscope (SEFM). Since the intensity of electrostatic force generated between the probe and the sample surface is relied on the differences of the CPD, the CPD can be calculated by using the frequency shifts of the probe oscillation when two different bias voltages are applied between tip and the sample. The detection sensitivity corresponding to the experimental conditions has been confirmed by simulation. In addition, the basic characteristic of the CPD measurement system has been evaluated.

Theoretical simulation of Kelvin probe force microscopy for Si surfaces by taking account of chemical forces

A new method of theoretical simulation for Kelvin probe force microscopy (KPFM) imaging on semiconductor or metal samples is proposed. The method is based on a partitioned real space (PR) density functional based tight binding (DFTB) calculation of the electronic states to determine the multi-pole electro-static force, which is augmented with the chemical force obtained by a perturbation treatment of the orbital hybridization. With the PR-DFTB method, the change of the total energy is calculated together with the induced charge distribution in the tip and the sample by their approach under an applied bias voltage, and the KPFM images, namely the patterns of local contact potential difference (LCPD) distribution, are obtained with the minimum condition of the interaction force. However, since the interaction force is due to electro-static multi-poles, the spatial resolution of the KPFM images obtained by PR-DFTB is limited to the nano-scale range and an atom-scale resolution cannot be attained. By introducing an additional chemical force, i.e., the force due to the orbital hybridization, we succeeded in reproducing atom-scale resolution of KPFM images. Case studies are performed for clean and impurity embedded Si surfaces with Si tip models.