Form Factors For Electron Research Articles

Stability, Reliability, and Robustness of GaN Power Devices: A Review

Gallium nitride (GaN) devices are revolutionarily advancing the efficiency, frequency, and form factor of power electronics. However, the material composition, architecture and physics of many GaN devices are significantly different from silicon and silicon carbide devices. These distinctions result in many unique stability, reliability and robustness issues facing GaN power devices. This paper reviews the current understanding of these issues, particularly those related to dynamic switching, and their impacts on system performance. Instead of delving into reliability physics, this paper intends to provide power electronics engineers the necessary information for deploying GaN devices in existing and emerging applications, as well as provide references for the qualification evaluations of GaN power devices. The issues covered in this paper include the dynamic instability of device parameters (e.g., on-resistance, threshold voltage, output capacitance), the device robustness in avalanche, overvoltage and short-circuit conditions, the device's switching reliability and lifetime, as well as the device's ruggedness under radiation and extreme (cryogenic and elevated) temperatures. Knowledge gaps and immediate research opportunities in the relevant fields are also discussed.

Reliability Test of Inkjet-Printable Silver Conductive Ink

Inkjet printing is a promising technique for fabricating printed electronics. This technique acquires the utilization of conductive ink to form a fine and thin resolution conductive structure on a flexible substrate. The challenges are to design a stable conductive ink with a controlled properties to prevent nozzle clogging. Furthermore, a fine structure construction often demonstrated poor device performance due low mechanical durability. In this work, we have characterized morphology of the newly developed inkjet-printable nanosilver conductive ink (Mi-Ag) in our laboratory. The ink shows a stable colloidal ink zeta potential of-79.1 mV with nanoparticle size less than 100 nm properties has been tailored for compatibility with inkjet printing of conductive pattern on polyethylene terephthalate (PET) flexible substrate. It has been ascertained that the flexible electronic form factor affects the quality of the physical and electrical properties of printed pattern and the device performance. Hence, the bending test of the printed RFID patterns fabricated with different layer of thicknesses was investigated. Electrical properties of the samples were monitored by in-situ conductivity and resistivity measurement under cyclic bending testing. Pattern with thinnest layer of 1.31μm (1X) had the smallest electrical properties percentage drop (38.4%) at 12,000 bending cycles due to the fact that in thick layer, the interparticle network started to change during bending and became weaker due to the large amount of the particles in the dense printed layer. In contrast, printed device exhibited minimal increase in resistivity. Consequently the particle gap increased which allowed the movement of electrons, leading to the increased of electrical resistance. The device endurance characteristic is crucial to satisfy future design requirement of flexible electronic applications.

Study Magnetic Electron Scattering Form Factor of Magnesium 24Mg

The magnetic form factors (ML) of inelastic electron scattering of magnesium nuclei 24Mg were studied computationally using Oxbash code. The energy levels of this nucleus were calculated through the shell model and using the model space (ZBM, PSD,SPSDPF and SD). For SD used two novel USD-type Hamiltonians, USDC and USDI, as well as modifications to these interactions, USDCm and USDIm. All the calculated values that were studied were compared with the available practical data, and it was also based on the data of the NNDC website. This study showed agreement between the calculated results and the experimental data after changing the values of g-factors where they were (𝑔𝑙 𝑝= 1.060 and 𝑔𝑙 𝑛= -0.060).

Electromagnetic Form Factors for 7,9,11Be Isotopes with Exact Center of Mass Correction

The shell model calculations with Cohen-Kurath (C-K) interaction were carried out to investigate form factors of elastic transverse electron scattering, and magnetic dipole-moments of odd 7,9,11Be isotopes. The effect of the exact value of center of mass correction was adopted to generate the magnetic form factors in Born approximation picture. The contribution of the higher 2p-shell configuration was included to reproduce the experimental data. A significant improvement was obtained in the present results with core-polarization (CP) effect through the effective g-factors. The occupancies percentage with respect to the valence nucleons was also calculated.

Elastic and inelastic form factors including 2-body short-range correlation effect

The charge distributions and elastic electron form factors for 18O, 42,44Ca, 58Ni, and 118Sn nuclei were considered using the cluster expansion of the 1- and 2-body terms. Inelastic electron form factors to 2+ states with core-polarization effects were studied, where the nuclear collective modes were considered alongside the shell model transition density. The influence of short-range correlations (SRCs) was calculated by the parameter β, which was introduced into the ground-state charge distribution and concluded the Jastrow-type function. It is found that the inclusion of 2-body correlations is necessary to describe the observed data of elastic and inelastic form factors at high momentum transfer q > 3 fm–1.

Pauli form factors of electron and muon in nonlocal quantum electrodynamics

Pauli form factors of electron and muon are studied in nonlocal quantum electrodynamics. We calculate one loop QED correction to their Pauli form factors. The relativistic regulator is generated by the correlation function in the nonlocal interaction. The cut-off parameter $\Lambda$ in the regulator is determined to get the consistent anomalous magnetic moments of electron and muon at the same level as local QED. When momentum transfer is large, there exists obvious difference between nonlocal and local QED.

Calculation of charge form factor of elastic electron scattering based on Skyrme force and relativistic eikonal approximation

We construct a scheme to calculate the charge form factors for the elastic electron scattering. Our calculation is based on the relativistic eikonal approximation and the Skyrme–Hartree–Fock equation. To perform our calculation and benchmark the results, eight model nuclei with available experimental data: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] are considered. For the comparison, the charge form factors calculated by the relativistic mean-field (RMF) model are also provided. Parameter set SLy5 is utilized for the Skyrme force, and the set NL3 is applied for the RMF model. It has been confirmed that combining of a nonrelativistic treatment for the target nucleus with a relativistic treatment for the incident electron may work better to reach highly descriptive and predictive results similar to the pure relativistic treatment. The results of this work are also useful for future experiments to test different inputs of densities for a specific nucleus.

Core-polarization effect in longitudinal electron scattering form factors of 65Cu nucleus

Inelastic longitudinal electron scattering form factors to 2+ and 4+ states in 65Cu nucleus has been calculated in the (2p3/2 1f 5/2 2p1/2) shell model space with the F5PVH effective interaction. The harmonic oscillator potential has been applied to calculate the wave functions of radial single-particle matrix elements. Two shell model codes, CP and NUSHELL are used to obtain results. The form factor of inelastic electron scattering to 1/21−, 1/22−, 3/22−, 3/23−, 5/21−, 5/22− and 7/2- states and finding the transition probabilities B (C2) (in units of e2 fm4) for these transitions and B (C4) (in units of e2 fm8) for the transition 7/2-, and comparing them with experimental data. Both the form factors and reduced transition probabilities with core-polarization effects gave a reasonable description of the experimental data.

Screen-Printed Piezoresistive Sensors for Monitoring Pressure Distribution in Wheelchair

Prolonged sitting inadequacies cause pressure ulcer to many individuals, especially to disadvantaged with reduced mobility. The measurement of distributed pressure and detection of irregular sitting postures is essential for preventing the risk of developing pressure ulcer. In this paper, a pressure sensing system capable of recognizing sitting postures by means of measuring interface pressure through printed pressure sensors is presented. A thin and flexible large area sensor is screen-printed using silver flake and carbon particle inks and comprises 16 sensing elements. For the evaluation of practical usability, the sensor characterization is carried out by conducting stability, repeatability, drift, and bending tests. The performance of the sensor is checked under varying environmental conditions. Sitting posture detection accuracy above 80 % is achieved using a classification algorithm for four different sitting postures. Pressure distribution is monitored at a scanning rate of 10 Hz. A low-power and small form factor of readout electronics enables a compact packaging inside the seat cushion. The presented sensor design targets smart wheelchairs, but it is extendable to much larger areas, for example, to be used in beds. The proposed sensing system would be of a great assistance for caregivers and health professionals.

Dynamical screening of AMM and QED effects for large-Z hydrogen-like atoms

The effective interaction ΔU AMM of the anomalous magnetic moment (AMM) of an electron with the Coulomb field of an extended nucleus is analyzed. As soon as the q 2 dependence of the electron formfactor F 2(q 2)is taken into account from the beginning, the AMM is found to be dynamically screened at small distances of r ≪ 1/m. The ΔU AMM effects on the low-lying electronic levels of a superheavy extended nucleus with Zα > 1are analyzed using the nonperturbative approach. The growth rate of the ΔU AMM contribution with increasing Z is shown to be essentially nonmonotonic. At the same time, the energy shifts of electronic levels in the vicinity of the threshold of the lower continuum monotonically decrease in the region Z ≫Z cr,1s . The latter result is generalized to the whole self-energy contribution to energy shifts of electronic levels, thus also referring to the possible behavior of QED radiative effects with virtual-photon exchange, considered beyond the framework of the perturbative expansion in Zα.

Radiation damage free ghost diffraction with atomic resolution

The x-ray free electron lasers can enable diffractive structural determination of protein nanocrystals and single molecules that are too small and radiation-sensitive for conventional x-ray diffraction. However the electronic form factor may be modified during the ultrashort x-ray pulse due to photoionization and electron cascade caused by the intense x-ray pulse. For general x-ray imaging techniques, the minimization of the effects of radiation damage is of major concern to ensure reliable reconstruction of molecular structure. Here we show that radiation damage free diffraction can be achieved with atomic spatial resolution by using x-ray parametric down-conversion and ghost diffraction with entangled photons of x-ray and optical frequencies. We show that the formation of the diffraction patterns satisfies a condition analogous to the Bragg equation, with a resolution that can be as fine as the crystal lattice length scale of several Ångstrom. Since the samples are illuminated by low energy optical photons, they can be free of radiation damage.

Ab initiosimulations of the dynamic ion structure factor of warm dense lithium

We present molecular dynamics simulations based on finite-temperature density functional theory that determine self-consistently the dynamic ion structure factor and the electronic form factor in lithium. Our comprehensive data set allows for the calculation of the dispersion relation for collective excitations, the calculation of the sound velocity, and the determination of the ion feature from the total electronic form factor and the ion structure factor. The results are compared with available experimental x-ray and neutron scattering data. Good agreement is found for both the liquid metal and warm dense matter domain. Finally, we study the impact of possible target inhomogeneities on x-ray scattering spectra.

Vladimir Sudakov and double-logarithmic asymptotics of amplitudes in QED, QCD and gravity

We review the Sudakov results on the double logarithmic asymptotics of the electron form-factor which were based on his parametrization of the virtual particle momenta in the Feynman diagrams. The high energy amplitudes for various QED and QCD processes in the double-logarithmic approximation are obtained by using the Bethe-Salpeter approach and the evolution equations. The ultraviolet divergency of the graviton Regge trajectory allows to derive the infrared evolution equation for the graviton-graviton scattering amplitude with a double-logarithmic accuracy. The asymptotic behavior of this amplitude depends essentially on the rank N of the super-symmetry.

The Impact of Stencil Printing Upon Assembly & Reliability Of 0.3mm Pitch CSP Components

Abstract With the continual shrinking of electronic assembly form factors, designers are being forced towards smaller, more complex components with decreasing interconnection pitches. As a consequence, the Surface Mount assembly process is becoming increasingly challenged. For the stencil printing process, this means that historically accepted stencil aperture area ratio design rules, (which dictate what can or cannot be printed), need to be significantly pushed to extend the printing process for next generation ultra -fine pitch components. As a result, a major study has been undertaken looking at several different aspects of the stencil printing process, and their impact upon the assembly and reliability of 0.3mm pitch CSP components. In a preliminary test, stencil printing factors such as stencil aperture size and printing technology (standard squeegees vs ultrasonically aided active squeegees) were investigated. Data showed that the active squeegees provided a significantly larger process window. Subsequently, components were assembled using a range of solder paste volumes printed with both standard and active squeegee technology. The components assembled using an active squeegee process exhibited higher assembly yield, and also extended reliability when subjected to thermal cycling.

Special issue on advanced flexible electronics for sensing applications [Scanning the Issue

This articles in this special issue on flexible hybrid electronics provides insight into the technical problems that must be overcome as well as the new capabilities they will provide. The term, 'flexible hybrid electronics' means different things based on the context in which it is being discussed. It could mean adaptable for multiple applications, but, here the term refers to mechanical properties, although not necessarily precisely defined. Mechanically flexible might mean anything from conformable (nonlinear shape) to bendable or rollable (around a defined radius of curvature), or even foldable and stretchable. Although not well defined, the intent is to differentiate from the rectangular, rigid form factor of conventional semiconductor electronics. Hybrid means heterogeneous integration of conventional electronics with other electronic components (passive devices, sensors, etc.) that could be fabricated using conventional thin-film transistor (TFT) process technology by additive printing (ink jet, gravure, etc.). The purpose is to provide an electronics solution that has adequate performance, but in a low cost, novel form factor because printing offers the ability to inexpensively fabricate structures over large areas on mechanically flexible substrates (plastics, metal sheets, bendable glass). However, integration with conventional electronics such as silicon CMOS is necessary to achieve required performance because TFT and printed devices are ignificantly inferior to conventionally fabricated devices.

Fast and accurate conversion of atomic models into electron density maps

New image processing methodologies and algorithms have greatly contributed to the signi cant progress in three-dimensional electron microscopy (3DEM) of biological complexes we have seen over the last decades. Naturally, the availability of accurate procedures for the objective testing of new algorithms is a crucial requirement for the further advancement of the eld. A good and accepted testing work ow involves the generation of realistic 3DEM-like maps of biological macromolecules from which some measure of ground truth can be derived, ideally because their 3D atomic structure is already known. In this work we propose a very accurate generation of maps using atomic form factors for electron scattering. We thoroughly review current approaches in the eld, quantitatively demonstrating the bene ts of the new methodology. Additionally, we study a concrete example of the use of this approach for hypothesis testing in 3D Electron Microscopy.

Magnetic Excitations in the Kondo Insulator SmB6

SmB6 is a Kondo insulator with surface conductivity that was recently proposed to be topologically protected. I shall describe an inelastic neutron scattering experiment probing magnetic excitations over a wide energy range in a single crystal of SmB6 at low temperatures. Consistent with previous findings by Alekseev et al., a resonant mode near 14 meV is observed at low temperatures near the X and R points of the Brillouin zone. The overall dispersion of the excitation is less than 1 meV. The intensity falls of rapidly in higher Brillouin zones as the 5d electron form factor. The comprehensive inelastic scattering data provide indirect information about the underlying, putative topological, hybridized band structure. Work at IQM was supported by the U.S. Department of Energy, office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-08ER46544. Work at ORNL was supported by LDRD 06576.

Ideas of four-fermion operators in electromagnetic form factor calculations

Four-fermion operators have been utilized in the past to link the quark-exchange processes in the interaction of hadrons with the effective meson-exchange amplitudes. In this presentation, we apply the similar idea of Fierz rearrangement to the electromagnetic processes and focus on the electromagnetic form factors of nucleon and electron. We explain the motivation of using four-fermion operators and discuss the advantage of this method in computing electromagnetic processes.

Ideas of four-fermion operators in hadron physics

Four-fermion operators have been utilized in the past to link the quarkexchange processes in the interaction of hadrons with the effective mesonexchange amplitudes. In this paper, we apply the similar idea of Fierz rearrangement to the electromagnetic processes and focus on the electromagnetic form factors of nucleon and electron. We explain the motivation of using four-fermion operators and discuss the advantage of this method in computing electromagnetic processes.

Theoretical study of the central depression of nuclear charge density distribution by electron scattering

The charge form factors of elastic electron scattering for isotones with N = 20 and N = 28 are calculated using the phase-shift analysis method, with corresponding charge density distributions from relativistic mean-field theory. The results show that there are sharp variations at the inner parts of charge distributions with the proton number decreasing. The corresponding charge form factors are divided into two groups because of the unique properties of the s-states wave functions, though the proton numbers change uniformly in two isotonic chains. Meanwhile, the shift regularities of the minima are also discussed, and we give a clear relation between the minima of the charge form factors and the corresponding charge radii. This relation is caused by the diffraction effect of the electron. Under this conclusion, we calculate the charge density distributions and the charge form factors of the A = 44 nuclei chain. The results are also useful for studying the central depression in light exotic nuclei.