Influence of contact potential difference and electric potential on the microhardness of metals

The effect of the electric potential on the microhardness of aluminum, zirconium, and ferrosilicon was studied experimentally. The effect of the proper electric potential applied to a sample is compared with the effect of the potential induced by the contact potential difference upon contact with metals with a different electron work function. These two types of electrical action are revealed to be qualitatively equivalent to each other. It is established that these effects can markedly (up to 15%) change the microhardness of the metals.     

Character of variation in the microhardness of the (0001) plane of Zn single crystals under the action of electrostatic field and the possible reason for this effect

The influence of electric potential on the microhardness of the crystallographic plane (0001) of zinc single crystals has been studied. It has been established that the microhardness decreases with an increase in the supplied potential and, at the value of 0.05 V, reaches saturation. The total decrease in the microhardness is 8%. It has been shown that the variation of the microhardness is statistically significant. The observed effect has been explained by a reduction in the surface energy density due to electrization of the surface. The reduction in the surface energy with allowance for the existing single layer of adsorbed water has been estimated.     

On the effect of electric potential on resistance of metals’ surface to microindentation

The effect of electric potential on the microindentation resistance is investigated experimentally for aluminum and zirconium samples. The effects of the electric potential proper applied to a sample and of the potential arising due to contact potential difference between metals with different electron work functions are compared. A qualitative equivalence of these two types of electrical action is revealed. A possibility of a significant (over 10%) change in the metal microhardness due to the above nentioned actions is established.     

Specific features of the thermodynamic equilibrium state of a thin water film in an electric field of surface active centers of a mica crystal

The structural features of a thin polar liquid film in an electric field of a charged substrate have been theoretically investigated using methods of statistical physics. It has been established that electrical interactions in this system lead to a change in the structure of the polar liquid and to the formation of clusters in it. A self-consistent nonlinear equation has been derived for describing the distribution of the potential and strength of the electric field inside the film under investigation. The depth of penetration of this field into the liquid medium has been studied as a function of the electrical activity of the substrate, temperature, degree of polarity of the liquid, and concentration of interface heterocharges. It has been revealed that the extent of structured regions in the liquid increases with an increase in the potential gradient of the internal field and with a decrease in the temperature.     

施加电场的半抛物量子阱中的电光效应

利用量子力学中的紧致密度矩阵方法，研究了施加电场的半抛物量子阱中的电光效应。通过位移谐振子变换，得到了系统中的电子态的精确解。对典型的GaAs材料进行数值计算的结果表明，随着电场强度的增加，电光效应系数几乎线性随之增加；但是随着半抛物量子阱受限势频率的增加，电光效应系数单调地减小；而且在同样的电场强度及抛物束缚势频率作用下，半抛物量子阱模型中的电光效应系数比抛物量子阱模型中的值大两个数量级，这是由于我们所选模型本身的非对称性以及电场进一步使这种非对称性增强的缘故。     

Effect of atomic hydrogen adsorption on the transport characteristics of semiconducting carbon nanotubes

The effect of atomic hydrogen adsorption on the conduction and diffusion properties of carbon nanotubes of zigzag type in an external electric field is considered. The model of adsorption of atomic hydrogen on the surface of single-walled carbon nanotubes of zigzag type is based on the single-impurity periodic Anderson model. The theoretical calculation of the diffusion coefficient and electrical conductivity of carbon nanotubes of zigzag type doped with hydrogen atoms is carried out in the relaxation time approximation. It has been revealed that the electrical conductivity and electron diffusion coefficient decrease with increasing concentration of adsorbed hydrogen atoms. It has been shown that the dependence of the electrical conductivity and the diffusion coefficient on the amplitude of the constant electric field at the constant concentration of hydrogen adatoms is nonlinear.     

Electrical field enhancement and laser damage growth in high-reflective coatings at 1064 nm

The effect of electric field enhancement on damage growth of flat bottom pit and nodule-ejected pit was studied based on the finite difference time domain method and temperature field theory. The electric field enhancement around the edge of damage pits indeed exists and varies from 1.2 to 2.0 times. It is found that damage growth not only depends on the electric field enhancement but also the local absorptive coefficient by temperature field calculation. The results also meet the reported damage growth behavior very well. A conclusion can be drawn that field enhancement and potential defects or new generated defects during former pulses are jointly responsible for the damage growth. In addition, an inference can be drawn from theoretical analysis that the flat bottom pit has been initiated by absorbing defect located at the H-L interfaces, which the peaks of electrical field happen to.     

压缩应变载荷下氮化镓隧道结微观压电特性及其巨压电电阻效应

电子器件可控性研究在日益追求器件智能化和可控化的当今社会至关重要. 基于第一性原理和量子输运计算, 本文研究了压缩应变载荷对氮化镓(GaN)隧道结基态电学性质和电流输运的影响, 在原子尺度上窥视了氮化镓隧道结的微观压电性, 验证了其内在的巨压电电阻(GPR)效应. 计算结果表明, 压缩应变载荷可以调节隧道结内氮化镓势垒层的电势能降、内建电场、电荷密度和极化强度, 进而实现对隧道结电流输运和隧穿电阻的调控. 在-1.0 V的偏置电压下, -5%的压缩应变载荷将使氮化镓隧道结的隧穿电阻增至4倍. 本研究展现了氮化镓隧道结在可控电子器件中的应用潜力, 也展现了应变工程在调控电子器件性能方面的光明前景.     

Influence of an electric field on the ferromagnetic resonance in a plane-layered magnetic system

The influence of an electric field on the ferromagnetic resonance (FMR) in a multilayer magnetic system consisting of two magnetic layers separated by a thin nonmagnetic interlayer has been investigated. It has been shown that, upon the excitation of magnetization oscillations by a microwave magnetic field, the eigenfrequencies of the ferromagnetic resonance depend on the stationary electric field applied in the plane of the layers. It has also been demonstrated that, in this system, high-frequency magnetization oscillations can be excited by an electric microwave field. The results of the investigation of the polarization properties of the excitation mechanism indicate that this effect can be observed experimentally.     

Analysis of the structural interaction of electrically active heterogeneous finely dispersed systems at the interfaces between the solid and liquid phases

Strong electrical forces have been revealed in electrically active heterogeneous finely dispersed systems at the interfaces between the solid and liquid phases. It has been established that these forces give rise to gradients of the potential of an internal self-electric field that can provide circulation of electric currents in the systems under investigation. It has been found that, in these systems, there arises a double electric layer that represents a new structuring phase, which is characteristic of electrically active systems only. The mechanism of formation of a double electric layer includes electrocontact interaction between the surfaces of two heterogeneous liquid and solid polar dielectrics.     

Effect of a weak external electric field on the kinetics of the ordering of ferroelectrics upon first-order phase transitions

The kinetics of the formation and growth of 180° domains in a weak quasi-stationary external electric field has been considered in the framework of the phenomenological Ginzburg–Landau model using the example of sodium nitrite (NaNO₂) crystals that undergo a first-order ferroelectric phase transition of the order–disorder type. The influence of the rate and temperature of quenching, as well as the strength of an external electric field, on the subsequent evolution of the system toward the thermodynamic equilibrium state has been analyzed. It has been shown that, by varying a weak external electric field applied to the ferroelectric crystal after quenching, it is possible to obtain both single-domain and multi-domain ordered structures. It has been established that the formation of nonequilibrium (“virtual”) multi-domain structures of the asymmetric type is possible for particular strengths of the electric field applied to the ferroelectric after quenching. A similar effect can be achieved by varying the depth of quenching of the sample. It has been found that, if the size of the order parameter inhomogeneities formed at the stage of quenching does not exceed a critical value, they can be reoriented partially or completely into domains of opposite sign. For this purpose, the relaxation after quenching should be performed in an external electric field of the appropriate sign.     

The effect of temperature and electric current on the phase state of Bi + 69 at % in alloy

The effect of temperature and constant electric current on the phase state of liquid-solid Bi + 69 at % In alloy has been investigated. It is shown that an electric current, depending on its direction, differently affects the shape, sizes, and orientation of solid inclusions near the liquidus line, thus changing the microhardness of crystallized alloys.     

Specific features of the dielectric response of heterogeneous systems with a polar matrix containing electrically active inclusions

A theoretical model has been proposed which makes it possible to introduce the correction into the complex permittivity of electrically active condensed systems that contain a polar liquid matrix and low-dimensional solid particles with a developed electrically active surface. It has been established that there is an interfacial electrical interaction between surface charges of the solid component and polar molecules of the liquid matrix. The processes occurring during this interaction lead to the appearance of an intrinsic internal electric field in the system under investigation. The contribution from surface effects to the formation of the polarized state of the polar liquid medium has been investigated in terms of the proposed model. The possibility of controlling the processes of local change in the structure of the polar liquid component under the effect of the internal electric field by varying the electrically active specific surface area of the solid phase and the intrinsic dipole moment of molecules of the liquid matrix has been analyzed in the studied systems. The conditions providing for the appearance of a controlled potential gradient of the internal electric field have been determined for the dispersed systems under consideration. The parameter that makes it possible to evaluate the contribution from the interfacial electrical contact interaction to the dielectric response of the liquid component and the entire system has been introduced for the first time.     

Impedance spectroscopy investigation of liquid crystals doped with ionic surfactants

The effect of a direct-current (dc) electric field on the electrophysical characteristics of nematic liquid crystals of the alkyl cyanobiphenyl series nCB (n = 6–8) and the multicomponent liquid-crystal mixture MB-1, which are doped with ionic surfactants, has been investigated using impedance spectroscopy. It has been found that the impedance spectra depend substantially on the dc bias voltage applied to the sample. The approximation of the measured spectra with specially developed equivalent circuits of the measuring cell with a sample has made it possible to determine the capacitance of the electric double layer and the electrical conductivity of the samples, as well as the mobility, concentration, and diffusion coefficient of the ions. It has been shown that a region of the space charge is formed in the frequency range f < 100 Hz near the electrodes of the measuring cell with a liquid-crystal sample, which leads to an increase in the active (resistive) and reactive (capacitive) components of the impedance.     

Dependence of space charge field and gain coefficient on the applied electric field in photorefractive materials

Intensity dependent space charge field and gain coefficient in the photorefractive medium due to the two interfering beams have been calculated by solving the material rate equations in presence of externally applied dc electric field. The gain coefficient has been studied with respect to variations in the input intensity, modulation depth, concentration ratio and normalized diffusion field in the absence and presence of the externally applied dc electric field. Space charge field has also been computed by varying the intensity ratio in the presence and absence of the externally applied dc electric field. It has been found that the rate of change of the space charge field with the normalized dc field decreases with the increasing intensity ratio for different values of the normalized diffusion field. It has also been found that the externally applied dc electric field has appreciable effect only when it is larger than the diffusion field.     

Stark shift and dissociation process of an ionized donor bound exciton in spherical quantum dots

The effect of an electric field on the ground state energy of an exciton bound to an ionized donor (D⁺, X) was studied in CdSe spherical quantum dots where quantum confinement is described by an infinitly deep potential. Calculations have been performed in the framework of the effective mass approximation using a variational method by choosing an appropriate sixty-terms wave function taking into account different interparticles correlations and symetry distorsion induced by the electric field. It appears that the Stark shift is significant even for low fields and depends strongly of spherical dot sizes. The competition between the confinement effect and the Stark effect is discussed as function of the spherical dot size and the applied electric field strength. The (D⁺, X) Stark shift is estimated and its behavior is discussed as a function of the dot radius and electric field strength. The electron and hole average distances have also been calculated and the role of the ionized donor in the excitonic dissociation is established.     

Magnetoelectric effect in perovskite quantum paraelectric EuTiO3

On the basis of successful theoretical explanation of the observed large magnetic-field effect (by ∼7% with 1.5 T) on the dielectric constant below the Néel temperature T_N of 5.5 K, we have demonstrated convincingly the magnetoelectric effect in an antiferromagnetic quantum paraelectric EuTiO₃ system. The mutual control of electric and magnetic properties is revealed by the variation of the electric-field-induced polarization with applied magnetic fields as well as the change of the magnetic-field-induced spin moments under the control of electric fields. It is found that the applied electric field (magnetic field) acts like a fictitious magnetic field (electric field) on the EuTiO₃ system. The magnetoelectric susceptibility is deduced to be proportional to the product of the magnetization, electrical polarization, magnetic susceptibility and dielectric susceptibility.     

Numerical simulations of electro-thermo-convection and heat transfer in 2D cavity

In this article the electro-thermo-convective phenomena in a dielectric liquid enclosed in a 2D cavity and subjected to the simultaneous action of an electric field and a thermal gradient is studied. We solved directly the full set of coupled equations of Electro-Hydro-Dynamic (EHD) and energy equation using a finite volume method. In order to characterize the influence of the electric field on heat transfer the liquid is first heated (from a lateral wall) till the thermal steady state is obtained and then the electric potential and injection of electric charge is applied. Two cases of injection are considered: from the lower electrode and from a lateral wall (left or right). The flow pattern and Nusselt number strongly depend on the non-dimensional characteristic parameters: electrical parameter, Rayleigh number, Prandtl number and mobility parameter M. The convective motion passing from a purely thermal convection to a purely electrical convection and the number of electro-thermo-convective rolls patterns are investigated.As a consequence of the analysis of the combined effect of electric and thermal fields on the flow structure and on Nusselt number, we have also evaluated the heat transfer enhancement due to electroconvection. It is shown that the injection of electric charge increases the heat transfer and Nusselt number is independent of Rayleigh number for high enough values of T.     

Electronic states in a Pöschl–Teller-like quantum well: Combined effects of electric field, hydrostatic pressure, and temperature

The work is devoted to present a theoretical study of the influences of external probes, such as applied electric field and hydrostatic pressure, on the electron and hole states in a Pöschl–Teller quantum well. The calculations have been done in the framework of the variational method. The dependence of the ground state energy of an electron and/or hole confined in the quantum well has been obtained as a function of the applied electric field and hydrostatic pressure. Different values of the asymmetry parameters of the Pöschl–Teller potential as well as temperature have been considered. It is shown that as a result of the increase in the electric field there is an augment of the ground state energy, and also that by increasing the quantum well width the effects of applied electric field are strengthened. It is obtained from the calculations that the ground state energy is a decreasing (increasing) function of the hydrostatic pressure (temperature). It is found that in the high pressure regime the energy grows with pressure, which is a previously unknown result. In the case of holes, the energy is always an increasing function both of the pressure and the temperature. Besides, the behavior of the photoluminescence peak energies associated to transitions between the ground states of electrons and heavy holes in the system is also reported.     

Ferroelectric phase transition in graphene with the Hubbard interaction

It has been revealed that, as an external dc electric field is applied to graphene with the Hubbard interaction between electrons, a spontaneous electric field perpendicular to the applied field can appear. This effect can be due to the nonequilibrium electron subsystem in graphene. The spontaneous field characteristics have been found as a function of the parameters of the problem.