Higher Order Multipole Potentials and Electrostatic Screening Effects on Cohesive Energy and Bulk Modulus of Metallic Nanoparticles

Higher order rnultipole potentials and electrostatic screening effects are introduced to incorporate the dan gling bonds on the surface of a metallic nanopaticle and to modify the coulornb like potential energy terms, respectively. The total interaction energy function for any rnetallic nanoparticle is represented in terms of two- and three-body potentials. The two-body part is described by dipole-dipole interaction potential, and in the three-body part, triple-dipole （DDD） and dipole-dipole-quadrupole （DDQ） terrns are included. The size-dependent cohesive energy and bulk modulus are observed to decrease with decreasing sizes, a result which is in good agreement with the experimental values of Mo and W nanoparticles.

The enhanced performance of piezoelectric nanogenerator via suppressing screening effect with Au particles/ZnO nanoarrays Schottky junction

This paper describes a novel strategy to weaken the piezopotential screening effect by forming Schottky junctions on the ZnO surface through the introduction of Au particles onto the surface. With this approach, the piezoelectric-energyconversion performance was greatly enhanced. The output voltage and current density of the Au@ZnO nanoarray-based piezoelectric nanogenerator reached 2 V and 1 μA/cm^2, respectively, 10 times higher than the output of pristine ZnO nanoarray-based piezoelectric nanogenerators. We attribute this enhancement to dramatic suppression of the screening effect due to the decreased carrier concentration, as determined by scanning Kelvin probe microscope measurements and impedance analysis. The lowered capacitance of the Au@ZnO nanoarraybased piezoelectric nanogenerator also contributes to the improved output. This work provides a novel method to enhance the performance of piezoelectric nanogenerators and possibly extends to piezotronics and piezophototronics.

Organic-semiconductor-assisted dielectric screening effect for stable and efficient perovskite solar cells

Perovskite solar cells(pero-SCs)performance is essentially limited by severe non-radiative losses and ion migration.Although numerous strategies have been proposed,challenges remain in the basic understanding of their origins.Here,we report a dielectric-screening-enhancement effect for perovskite defects by using organic semiconductors with finely tuned molecular structures from the atoms level.Our method produced various perovskite films with high dielectric constant values,reduced charge capture regions,suppressed ion migration,and it provides an efficient charge transport pathway for suppressing non-radiative recombination beyond the passivation effect.The resulting pero-SCs showed a promising power conversion efficiency(PCE)of 23.35%with a high open-circuit voltage(1.22 V);and the 1-cm^(2) pero-SCs maintained an excellent PCE(21.93%),showing feasibility for scalable fabrication.The robust operational and thermal stabilities revealed that this method paved a new way to understand the degradation mechanism of pero-SCs,promoting the efficiency,stability and scaled fabrication of the pero-SCs.

Illumination-dependent free carrier screening effect on the performance evolution of ZnO piezotronic strain sensor

Performance modulation of ZnO optoelectronic devices in the presence of proper piezoelectric polarization charges has been widely reported, whereas relatively less work has been performed about the influence of photoexcitation on piezotronics. In this stud~ we experimentally investigated the performance evolution of ZnO piezotronic strain sensor under various 365 nm UV irradiation densities. The device demonstrated a response ratio of -200 under no illumination and under -0.53% compressive strain, and the response time is approximately 0.3 s. However, tremendous performance degradation was observed with the increase in the illumination densi~, which is attributed to the W-modulated change in the free electron concentration and Schottky barrier height. It was observed that increased carrier density intensifies the screening effect and thus, the modulation ability of piezo-polarization charges weakens. Meanwhile, the deterioration of rectifying behavior at the interface under UV illumination also jeopardizes the device performance.

Screening effects on ^(12)C+^(12)C fusion reaction

One of the important reactions for nucleosynthesis in the carbon burning phase in high-mass stars is the12C+12C fusion reaction. In this study, we investigate the influences of the nuclear potentials and screening effect on astrophysically interesting12C+12C fusion reaction observables at sub-barrier energies by using the microscopic α-αdouble folding cluster(DFC) potential and the proximity potential. In order to model the screening effects on the experimental data, a more general exponential cosine screened Coulomb(MGECSC) potential including Debye and quantum plasma cases has been considered in the calculations for the12C+12C fusion reaction. In the calculations of the reaction observables, the semi-classical Wentzel-Kramers-Brillouin(WKB) approach and coupled channel(CC)formalism have been used. Moreover, in order to investigate how the potentials between12C nuclei produce molecular cluster states of24Mg, the normalized resonant energy states of24Mg cluster bands have been calculated for the DFC potential. By analyzing the results produced from the fusion of12C+12C, it is found that taking into account the screening effects in terms of MGECSC is important for explaining the12C+12C fusion data, and the microscopic DFC potential is better than the proximity potential in explaining the experimental data, also considering that clustering is dominant for the structure of the24Mg nucleus.

The effect of dynamical screening on helium(e,2e) fully differential cross-sections

This paper presents the fully differential cross sections （FDCS） for 102eV electron impact single ionization of helium for both the coplanar and perpendicular plane asymmetric geometries within the framework of dynamically screened three-Coulomb-wave theory. Comparisons are made with the experimental data and those of the three-Coulomb wave function model and second-order distorted-wave Born method. The angular distribution and relative heights of the present FDCS is found to be in very good agreement with the experimental data in the perpendicular plane geometry. It is shown that dynamical screening effects are significant in this geometry. Three-body coupling is expected to be weak in the coplanar geometry, although the precise absolute value of the cross section is still sensitive to the interaction details.

Time behavior of field screening effects in small-size GaAs photoconductive terahertz antenna

The field screening effects in small-size GaAs photoconductive （PC） antenna are investigated via the well-known pump and probe terahertz （THz） generation technique. The peak amplitude of the THz pulses excited by the probe laser pulse as a function of the pump-probe time delay was measured. An equivalent-circuit model was used to simulate the experimental data. Based on the good agreement between the results of simulation and experiment, the time behavior of the radiation and space-charge fields was simulated. The results show that the spacecharge screening dominantly determines the device response in the whole time, while the radiation filed screening plays a key role in initial time which strongly affects the peak THz field. The parameter analysis was performed, which may be valuable on the optimum design for the antenna as a THz emitter.

Assessing the Effectiveness of a Cervical Cancer Screening Program in a Hospital-based Study

This study compared HPV testing and liquid-based cytology （LCT） as performance indicators for cervical cancer screening in a hospital-based study. A total of 61,193 outpatients were screened initially by LCT. Samples with screening results showing atypical squamous cells of undetermined significance （ASC-US） or worse were referred for colposcopy, and some samples were tested for high-risk HPV types with the Hybrid Capture II system （HC II）. Data on LCT （n=61,193） and HC II （n=1056） results were analysed. Overall test positivity for LCT was 2.53% using an ASC-US threshold, 3.11% using a low-grade squamous intraepithelial lesion （LSIL） threshold, and 0.67% using a high-grade squamous intraepithelial lesion （HSIL） threshold. A total of 1839 women （84% of the 3893 patients with abnormal cytology） underwent colposcopy-directed biopsy. HPV was positive in 80.3% of women with cervical intraepithelial neoplasia 1 （CIN1）, 88.3% of those with CIN2, 79.2% of women with CIN3 and 50% （2 of 4） of women with invasive cancer. There was a significant increase in the detection of CIN2 or worse with adjunct HPV testing of women with ASC-US and LSIL However, there were detection of CIN2＋ cases no differences in the with adjunct HPV testing of women with HSlI.. The results indicate that HPV testing for HSlL triage should not be recommended in cervical cancer screening.

Velocity Form Calculations of Generalized Oscillator Strengths for 3s→ (3p, 4p, 5p, 6p) Dipole Transitions of Atomic Sodium in Debye Plasma

In this paper, the generalized oscillator strengths (GOSs) of excitations of atomic sodium from ground state to 2p63s0 (3p, 4p, 5p, 6p) states, immersed in Debye plasma, were calculated by using wavefunctions which were obtained numerically from the restricted Hartree-Fock (RHF) equation. This RHF equation employs the local density approach for exchange interactions including plasma Debye screening. Theoretical RHF and random phase approximation with exchange (RPAE) velocity calculations have shown that the GOSs for excitations to 3 s0(3 p,4 p,5 p,6 p)depend on the plasma Debye screening effects, as shown by the reduction in the GOS amplitude with decreasing Debye length λD. The agreement between the present RPAE V results for the transitions 3 s→3 s0(3 p,4 p,5 p)and the length calculations of Martínez-Flores was satisfactory. Correlation effects were found quite to be significant in the vicinity of the maxima of the GOS of the 3 s→3 s0(4 p,5 p,6 p)excitations by using the RPAE V approach. We note the poor influence of many electron correlations on the GOS of (3 s→3 p)transition with the same principal quantum number. Finally, we comment that the RPAE V calculations are useful in investigating electron correlation effects on the transition GOS of atomic sodium planted in Debye plasma. The present velocity results also reveal that the 3 s→3 s0(5p, 6p)transition GOSs tend to be delocalized due to more significant screening effects at Debye lengths λD=20and 30 a.u. for excited subshells 5p and 6p, respectively. We report here novel results of GOS for 3 s→3 s06ptransition obtained from different Debye lengths.

Screening of plane S waves by an array of rigid piles in poroelastic soil

An array of rigid piles used as a screening barrier for plane shear (S) waves is investigated in a homogeneous unbounded space. The dynamic poroelastic theory of Biot is employed, under the assumption of an incompressible solid grain. Using Fourier-Bessel series, the problem of multiple scattering is solved by imposing continuity conditions and equilibrium conditions at the soil-pile interfaces with the translational addition theorem. A parametric analysis is conducted to investigate the influence of the permeability of poroelastic soil, separation between piles, number of piles and frequency of incident waves on screening effectiveness of the barrier, and the results are compared with those in an elastic soil medium. Computed results show that the intrinsic permeability of the soil medium displays an apparent effect on the screening of plane S waves.

Nonlinear magneto-mechanical-thermo coupling characteristic analysis for transport behaviors of carriers in composite multiferroic piezoelectric semiconductor nanoplates with surface effect

In this paper,to better reveal the surface effect and the screening effect as well as the nonlinear multi-field coupling characteristic of the multifunctional piezoelectric semiconductor(PS)nanodevice,and to further improve its working performance,a magneto-mechanical-thermo coupling theoretical model is theoretically established for the extensional analysis of a three-layered magneto-electro-semiconductor coupling laminated nanoplate with the surface effect.Next,by using the current theoretical model,some numerical analyses and discussion about the surface effect,the corresponding critical thickness of the nanoplate,and the distributions of the physical fields(including the electron concentration perturbation,the electric potential,the electric field,the average electric displacement,the effective polarization charge density,and the total charge density)under different initial state electron concentrations,as well as their active manipulation via some external magnetic field,pre-stress,and temperature stimuli,are performed.Utilizing the nonlinear multi-field coupling effect induced by inevitable external stimuli in the device operating environment,this paper not only provides theoretical support for understanding the size-dependent tuning/controlling of carrier transport as well as its screening effect,but also assists the design of a series of multiferroic PS nanodevices.

Stability of the positively charged manganese centre in GaAs heterostructures examined theoretically by the effective mass approximation calculation near the Γ critical point

This paper describes an n-i-p-i-n model heterostructure with a manganese （Mn）-doped p-type base region to check the stability of a positively charged manganese A＋Mn centre with two holes weakly bound by a negatively charged 3dS（Mn） core of a local spin S = 5/2 in the framework of the effective mass approximation near the F critical point （k -0）. By including the carrier screening effect, the ground state energy and the binding energy of the second hole in the positively charged centre A＋Mn are calculated within a hole concentration range from 1 ×10^16 cm-3 to 1 × 10^17 cm^-3, which is achievable by biasing the structure under photo-excitation. For comparison, the ground-state energy of a single hole in the neutral AMn centre is calculated in the same concentration range. It turns out that the binding energy of the second hole in the A＋Mn centre varies from 9.27 meV to 4.57 meV. We propose that the presence of the A＋Mn centre can be examined by measuring the photoluminescence from recombination of electrons in the conduction band with the bound holes in the A＋Mn centre since a high frequency dielectric constant of ε∞ = 10.66 can be safely adopted in this case. The novel feature of the ability to tune the impurity level of the A＋Mn centre makes it attractive for optically and electrically manipulating local magnetic spins in semiconductors.

Screening of a Test Charge in Plasma

Nonlinear screening of a test charge in plasma by electrons trapped or untrapped is studied. The obtained results are in rigorous estimations mathematically in comparison with the corresponding Debye screening forms.Meanwhile their validity is physically discussed and some confusions in literature are clarified.

Force measurement between mica surfaces in electrolyte solutions

The forces between two molecularly smooth mica surfaces are measured in monovalent and divalent cations electrolyte solutions by a surface force apparatus （SFA）. The properties of K＋, Na＋, and Mg2＋ between molecularly smooth mica surfaces are investigated. The Derjagui-Landau- Verwey-Overbeek （DLVO） force and the hydration force are detected in the experiment. The results show that in lower concentrations of a monovalent electrolyte solution （about 10-4 mol/L）, the force curves are completely in good agreement with those computed by the DLVO theory. However, additional short-range repulsive forces which deviate from the DLVO theory are observed when the concentrations of cations are above the critical bulk concentration, which is different for each electrolyte. The results show the properties of these cations on both the screening effect adsorbed on the mica surface and the hydration in solution. From the results, the interaction energy between two hydrated ions of potassium or sodium can also be estimated.

Binding Energies of Screened Excitons in a Strained(111)-Oriented Zinc-Blende GaN/AlGaN Quantum Well Under Hydrostatic Pressure

We investigate the binding energies of excitons in a strained （111）-oriented zinc-blende GaN/Al0.3 Ga0.7 N quantum well screened by the electron-hole （e-h） gas under hydrostatic pressure by combining a variational method and a selfconsistent procedure. A built-in electric field produced by the strain-induced piezoelectric polarization is considered in our calculations. The result indicates that the binding energies of excitons increase nearly linearly with pressure,even though the modification of strain with hydrostatic pressure is considered, and the influence of pressure is more apparent under higher e-h densities. It is also found that as the density of an e-h gas increases,the binding energies first increase slowly to a maximum and then decrease rapidly when the e-h density is larger than about 1 ×10^11 cm^-2. The excitonic binding energies increase obviously as the barrier thickness decreases due to the decrease of the built-in electric field.

Application of the homotopy analysis method to nonlinear characteristics of a piezoelectric semiconductor fiber

Based on the nonlinear constitutive equation,a piezoelectric semiconductor(PSC)fiber under axial loads and Ohmic contact boundary conditions is investigated.The analytical solutions of electromechanical fields are derived by the homotopy analysis method(HAM),indicating that the HAM is efficient for the nonlinear analysis of PSC fibers,along with a rapid rate of convergence.Furthermore,the nonlinear characteristics of electromechanical fields are discussed through numerical results.It is shown that the asymmetrical distribution of electromechanical fields is obvious under a symmetrical load,and the piezoelectric effect is weakened by an applied electric field.With the increase in the initial carrier concentration,the electric potential decreases,and owing to the screen-ing effect of electrons,the distribution of electromechanical fields tends to be symmetrical.

Effect of carrier screening on ZnO-based resistive switching memory devices

The carrier screening effect occurs commonly in dielectric materials. It reduces the electric potential gradient, thus negatively affecting the functionality of resistive random access memory （RRAM） devices. An Au/ZnO film/Al-doped ZnO device fabricated in this work exhibited no resistive switching （RS）, which was attributed to the carrier screening effect. Therefore, annealing was used for alleviating the screening effect, significantly enhancing the RS property. In addition, different on/off ratios were obtained for various bias values, and the screening effect was accounted for by investigating electron transport mechanisms. Furthermore, different annealing temperatures were employed to modulate the free carrier concentration in ZnO films to alleviate the screening effect. The maximal on/off ratio reached 10s at an annealing temperature of 600 ℃, yielding the lowest number of free carriers and the weakest screening effect in ZnO films. This work investigates the screening effect in RS devices. The screening effect not only modulates the characteristics of memory devices but also provides insight into the mechanism of RS in these devices.

Interfacial Polymer Engineered Field Effect Transistor Biosensors for Rapid and Efficient Identification of SARS-CoV-2 N Antigen

With the advantages of high sensitivity,rapid response,label-free,and simple operation,field effect transistor biosensors have shown promising application prospects in large-scale pathogen screening.However,in practical biological fluids with relatively high ionic strength,such as saliva and serum,the Debye screening effect will weaken the interaction between FET biosensors and target bio-molecules,thereby affecting the sensing sensitivity and accuracy.

Edge and Core Impurity Transport Study With Spectroscopic Instruments in LHD

Impurity transport was investigated at both edge and core regions in large helical de- vice （LHD） with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The edge impurity behavior was studied recently using four carbon resonant transitions in different ionization stages of CIII （977A）, CIV （1548A）, CV （40.3A） and CVI （33.7A）. When the line-averaged electron density, ne, is increased from 1 to 6 × 10^13 cm-3, the ratio of （CIII^CIV）/ne increases while the ratio of （CV＋CVI）/ne decreases. Here, CIII^CIV （CV＋CVI） expresses the sum of CIII （CV） and CIV （CVI） intensities. The CIII＋CIV indicates the carbon influx and the CV＋CVI indicates the emissions through the transport in the ergodic layer. The result thus gives experimental evidence on the impurity screening by the ergodic layer in LHD, which is also supported by a three-dimensional edge particle simulation. The core impu- rity behavior is also studied in high-density discharges （ne 〈 1 × 10^15 cm 3） with multi H2-pellets injection. It is found that the ratio of V/D （V： convection velocity, D： diffusion coefficient） decreases after pellet injection and Zeff profile shows a flat one at values of 1.1,-1.2. These results confirm no impurity accumulation occurs in high-density discharges. As a result, the iron density, rife, is analyzed to be 6 × 10^-7（=- nFe/ne） of which the amount can be negligible as radiation source even in such high-density discharges. One- and two-dimensional impurity distributions from space-resolved VUV and EUV spectrometers newly developed for further impurity transport study are also presented with their preliminary results.