Search results for "EFF"
showing 10 items of 13980 documents
Magnetic properties of exciton trapped by an off-center ionized donor in single quantum dot
2021
Abstract It is known that the lines of exciton (X) and exciton trapped by an ionized donor ( D + , X ) are often very close which makes very difficult their experimental identification. In order to facilitate their distinction in spherical quantum dots, we investigate the effect of an applied magnetic field studying the binding energy of the complex ( D + , X ) as function of dot size and the ionized donor position. Our calculation is using a variational approach taking into account the interactions between all charge carriers. Our results show that the complex is more sensitive to the magnetic field than the exciton and that the energy of the exciton is not sufficiently affected when the i…
Enhancement of the Multipactor Threshold Inside Nonrectangular Iris
2018
Multipactor breakdown is studied inside the capacitive iris of a rectangular waveguide with a skewed slot along its longitudinal cross section. Both the iris length and height are assumed to be small compared to the electromagnetic wavelength. Therefore, the quasi-static approximation is applied so as to describe the RF field distribution inside the iris gap, whereas a 2-D model is used to analyze the electron motion. The peculiarities of RF field structure are studied using the conformal mapping approach, which shows that the electric field lines can be approximated by circular arcs when the iris length is much larger than its height. The electron motion inside the iris gap is analyzed usi…
Transport properties of Bi2Sr2Ca2Cu3O10+δ Bicrystal Grain Boundary Josephson Junctions and SQUIDs
1996
Josephson junctions and SQUIDs on 36.8° SrTiO 3 bicrystal substrates were prepared from epitaxial Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ thin films with critical temperatures around 95K. The current-voltage characteristics are well described by the resistively and capacitively shunted junction model. I c R n products of 50μV at 77K and 0.7mV at 4.2K have been reached. The I c (B) dependence is symmetric to B = 0 with an I c suppression of 90% in the first minimum. Nevertheless it turns out, that the junctions are inhomogeneous on a μm scale. SQUID modulations observed at 78K indicate a flux-voltage transfer function of 2.7μV/Φ 0 at this temperature.
Temperature Coefficients of Solar Cell Parameters at Maximum Power Point
2020
Analytical expressions for the temperature coefficients of the maximum power point voltage and current are presented. The temperature coefficients are calculated assuming the bandgap to be a linear function of the temperature and accounting for energy losses of non-radiative nature. The latter are introduced in the model through the External Radiative Efficiency. The so-called $\gamma$ parameter, which has been shown to account for the thermal sensitivity of all mechanisms determining the open-circuit voltage, appears to also play a role in the temperature coefficient of the maximum power point voltage and current. Numerical results and a comparison with experimental measurements are also p…
Calculation of the electrostatic field in a dielectric-loaded waveguide due to an arbitrary charge distribution on the dielectric layer
2016
The goal of this paper is to study the electrostatic field due to an arbitrary charge distribution on a dielectric layer in a dielectric-loaded rectangular waveguide. In order to obtain this electrostatic field, the potential due to a point charge on the dielectric layer is solved in advance. The high computational complexity of this problem requires the use of different numerical integration techniques (e.g., Filon, Gauss-Kronrod, Lobatto, …) and interpolation methods. Using the principle of superposition, the potential due to an arbitrary charge distribution on a dielectric layer is obtained by adding the individual contribution of each point charge. Finally, a numerical differentiation o…
Influence of “Productive” Impurities (Cd, Na, O) on the Properties of the Cu 2 ZnSnS 4 Absorber of Model Solar Cells
2021
The research has been supported by grant of the Ministry of Education and Science of the Republic of Kazakhstan AP09562784. The authors (D. Sergeyev) acknowledges the provision of SCAPS-1D software by Prof. Marc Burgelman. The research of A.I. Popov has been supported by the Institute of Solid State Physics (ISSP), University of Latvia (UL). ISSP UL as the Centre of Excellence is supported through the Framework Program for Euro-pean Universities Union Horizon 2020, H2020-WIDESPREAD-01–2016–2017-TeamingPhase2 under Grant Agreement No. 739508, CAMART2 project.
Towards quantum phase slip based standard of electric current
2019
An accurate standard of electric current is a long-standing challenge of modern metrology. It has been predicted that a superconducting nanowire in the regime of quantum fluctuations can be considered as the dynamic equivalent of a chain of conventional Josephson junctions. In full analogy with the quantum standard of electric voltage based on the Josephson effect, the quantum phase slip phenomenon in ultrathin superconducting nanowires could be used for building the quantum standard of electric current. This work presents advances toward this ultimate goal.
A graphene-based neutral particle detector
2019
A neutral particle detector is presented, in which the traditionally used target material, indium tin oxide (ITO), is replaced by graphene. The graphene-based detector enables collinear photodetachment measurements at a significantly shorter wavelength of light down to 230 nm compared to ITO-based detectors, which are limited at 335 nm. Moreover, the background signal from the photoelectric effect is drastically reduced when using graphene. The graphene based detector, reaching 1.7 eV further into the UV energy range, allows increased possibilities for photodetachment studies of negatively charged atoms, molecules, and clusters.A neutral particle detector is presented, in which the traditio…
Enhancement of the Spin Pumping Effect by Magnon Confluence Process in YIG/Pt Bilayers
2019
The experimental investigation of the spin pumping process by dipolar‐exchange magnons parametrically excited in in‐plane magnetized yttrium iron garnet/platinum bilayers is presented. The electric voltage generated in the platinum layer via the inverse spin Hall effect (ISHE) results from contributions of two opposite spin currents formed by the longitudinal spin Seebeck effect and by the spin pumping from parametric magnons. In the field‐dependent measurements of the spin pumping‐induced component of the ISHE‐voltage, a clearly visible sharp peak is detected at high pumping powers. It is found that the peak position is determined by the process of confluence of two parametrically excited …
High transparency Bi 2 Se 3 topological insulator nanoribbon Josephson junctions with low resistive noise properties
2019
Bi$_2$Se$_3$ nanoribbons, grown by catalyst-free Physical Vapour Deposition, have been used to fabricate high quality Josephson junctions with Al superconducting electrodes. The conductance spectra (dI/dV) of the junctions show clear dip-peak structures characteristic of multiple Andreev reflections. The temperature dependence of the dip-peak features reveals a highly transparent Al/Bi$_2$Se$_3$ topological insulator nanoribbon interface and Josephson junction barrier. This is supported by the high values of the Bi$_2$Se$_3$ induced gap and of I$_c$R$_n$ (I$_c$ critical current, R$_n$ normal resistance of the junction) product both of the order of 160 $\mu$eV, a value close to the Al gap. T…