Study Of Field Effects Research Articles

Electric-Field-Induced Superconductivity on an Organic/Oxide Interface

Many superconductors have been developed by inducing charge carriers into a mother insulator compound. Chemical substitution of impurity atoms is usually used for inducing charge carriers, and this method is called “chemical doping”. Another method to tune charge carrier density is the electric field effect, which is widely utilized as a field-effect transistor. Here, we review recent progress in an electric field-effect study for developing a new oxide superconductor with an organic electrolyte gate. We first present a device configuration of an electric double layer transistor with oxide semiconductors, SrTiO3 and KTaO3. We then present the electrochemical interface properties and room-temperature device characteristics with various electrolytes. Finally, we present the superconductivity emerging at an organic/oxide interface, and discuss the phase diagram of electric-field-induced superconductors by comparing with superconductors obtained by chemical doping.

In vivo experimental study of nanosecond pulsed electric field effects on solid tumors

Many studies have tested the application of pulsed electric fields to tumors during cancer therapy. In this study, we used an embryonic chick assay to test the effects of nanosecond pulsed electric fields (nsPEFs) on a solid tumor. Our experiments used the embryonic chick assay, which is classified as in vivo experiment, because it has several advantages. Mouse breast adenocarcinoma cell line EMT6/KU was used to produce tumor cells for the experiment. The cells were inoculated for several days before the test and nsPEFs were applied using needle electrodes to solid tumors formed on the chorioallantoic membrane of eggs. A pulsed power generator with a pulse output length of 1.5 ns was used in this experiment. The tumors were dissected from the eggs after several days of nsPEF application and weighed. The mean weight of tumors treated with pulses was less than that of the control. The difference between the weight of the tumor after nsPEF application and that of the control was significant. The difference increased with the charging voltage of the pulsed power generator, with significant different observed when the charging voltage of the pulsed power generator was >2.85 kV. The mean tumor weight of the group that experienced discharges infrequently occurred on or under CAM was significantly smaller than that of the group that did not experience.

Magnetic field-dependent of binding energy in GaN/InGaN/GaN spherical QDQW nanoparticles

Simultaneous study of magnetic field and impurity's position effects on the ground-state shallow-donor binding energy in GaN│InGaN│GaN (core│well│shell) spherical quantum dot–quantum well (SQDQW) as a function of the ratio of the inner and the outer radius is reported. The calculations are investigated within the framework of the effective-mass approximation and an infinite deep potential describing the quantum confinement effect. A Ritz variational approach is used taking into account of the electron-impurity correlation and the magnetic field effect in the trial wave-function. It appears that the binding energy depends strongly on the external magnetic field, the impurity's position and the structure radius. It has been found that: (i) the magnetic field effect is more marked in large layer than in thin layer and (ii) it is more pronounced in the spherical layer center than in its extremities.

On field effect studies and superconductor-insulator transition in high-Tc cuprates

We summarize previous field effect studies in high-T (c) cuprates and then discuss our method to smoothly tune the carrier concentration of a cuprate film over a wide range using an applied electric field. We synthesized epitaxial one-unit-cell thick films of La2-x Sr (x) CuO4 and from them fabricated electric double layer transistor devices utilizing various gate electrolytes. We were able to vary the carrier density by about 0.08 carriers per Cu atom, with the resulting change in T (c) of 30 K. The superconductor-insulator transition occurred at the critical resistance very close to the quantum resistance for pairs, R (Q) = h/(2e)(2) = 6.5 k Omega. This is suggestive of a quantum phase transition, possibly driven by quantum phase fluctuations, between a Bose insulator and a high-T (c) superconductor state.

Theoretical investigation of stark effect on shallow donor binding energy in InGaN spherical QD-QW

In this paper, a simultaneous study of electric field and impurity's position effects on the ground-state shallow-donor binding energy in GaN│InGaN│GaN spherical quantum dot-quantum well (SQD-QW) as a function of the ratio of the inner and the outer radius is reported. The calculations are investigated using variational approach within the framework of the effective-mass approximation. The numerical results show that: (i) the binding energy is strongly affected by the external electric field and the SQD-QW dimension, (ii) a critical value of spherical system's radius is obtained constituting the limit of three dimension confinement and spherical thin layer confinement and (iii) the Stark shift increases with increasing electric field and it is more pronounced around the position of the impurity corresponding to the binding energy maxima than in the spherical layer extremities.

Bottom-up synthesis of ultrathin straight platinum nanowires: Electric field impact

We present a study of the electric field effect on electrochemically grown ultrathin, straight platinum nanowires with minimum diameter of 15 nm and length in the micrometer range, synthesized on a silicon oxide substrate between metal electrodes in H2PtCl6 solution. The influence of the concentration of the platinumcontaining acid and the frequency of the applied voltage on the diameter of the nanowires is discussed with a corresponding theoretical analysis. We demonstrate for the first time that the electric field profile, provided by the specific geometry of the metal electrodes, dramatically influences the growth and morphology of the nanowires. Finally, we provide guidelines for the controlled fabrication and contacting of straight, ultrathin metal wires, eliminating branching and dendritic growth, which is one of the main shortcomings of the current bottom-up nanotechnology. The proposed concept of self-assembly of thin nanowires, influenced by the electric field, potentially represents a new route for guided nanocontacting via smart design of the electrode geometry. The possible applications reach from nanoelectronics to gas sensors and biosensors.

Scanning tunneling microscopy of gate tunable topological insulator Bi2Se3thin films

Electrical field control of the carrier density of topological insulators (TI) has greatly expanded the possible practical use of these materials. However, the combination of low temperature local probe studies and a gate tunable TI device remains challenging. We have overcome this limitation by scanning tunneling microscopy and spectroscopy measurements on in-situ molecular beam epitaxy growth of Bi2Se3 films on SrTiO3 substrates with pre-patterned electrodes. Using this gating method, we are able to shift the Fermi level of the top surface states by 250 meV on a 3 nm thick Bi2Se3 device. We report field effect studies of the surface state dispersion, band gap, and electronic structure at the Fermi level.

Critical Electric Field of InGaN p-i-n Solar Cell

We present a study of electric field effect on the efficiency of GaN/In0.1Ga0.9N p-i-n solar cells by using the advanced physical models of semiconductor devices (APSYS) simulation program. In this study, the electric field strength and other parameters such as optimum thickness of p-type layer and efficiency of GaN/In0.1Ga0.9N p-i-n solar cells with different i-layer thicknesses have been performed. On the basis of simulating results, for a high efficiency solar cell, it is found that the optimum p-type layer concentration is above 4×1016 cm-3 and the suitable thickness is between 0.1 to 0.2 μm. For different i-layer thickness and p-doping concentrations, a critical electric field (Fc) has been found at 100 kV/cm. It is worth to note that when the electric field strength of i-layer below Fc value, the solar cell efficiency will dramatically decrease. Thus Fc can be seen as an index for acquiring the quality of solar device.

Iron tetraphenyl porphyrin functionalized single wall carbon nanotubes for the detection of benzene

Non-covalently functionalized SWNTs with iron tetraphenyl porphyrin (FeTPP) were employed for detection of benzene in a sensing window of 125ppm at room temperature. Formation of the SWNTFeTPP complex was confirmed by morphological, electrical and field effect studies that revealed an electron donating nature of porphyrin. The SWNTFeTPP sensor showed an average sensitivity of 62% and excellent linearity for validated window of concentration. The typical response and recovery time of the sensor were recorded to be in the order of seconds. In comparison to the sensing behavior of SWNTTPP (tetraphenyl porphyrin) sensor, the SWNTFeTPP sensor exhibited a superior sensing. The central metal ion in case of FeTPP functionalized sensor is found to be instrumental in deciding the sensing behavior.

Density Functional Theory study of electric field effects on CO and OH adsorption and co-adsorption on gold surfaces

A Density Functional Theory (DFT) study of CO and OH adsorption on Au(111) and Au(110) surfaces is presented. The analysis includes the effect of an external negative electric field on adsorption characteristics such as binding energies, binding geometries, charge distribution and vibrational frequencies, both on CO and OH individually and in co-adsorbed geometries. The minimal energy pathways for COOH formation from CO and OH co-adsorbed on Au(111) and Au(110) were also calculated. The ability of CO to enhance the adsorption of OH on gold is discussed in relation to the surface structure of gold and changes in the work function as induced by the adsorption of CO.

Application of magnetic field for biological response modification

The study of magnetic effects on biological system was started in response to Dr. Nose's wish for the development of extracorporeal immunomodulation therapy. In the extracorporeal immunomodulation system, monocytes or lymphocytes in blood are stimulated by the interactions with immune-active materials. The concept of magnetic field application was introduced in order to enhance the cell activation. Therefore, the applicability of magnetic field was studied. This paper was concerned with in vitro study of magnetic field effects on macrophage/monocytes and lymphocytes activations. Time-varying magnetic field could enhance macrophages/monocytes and lymphocytes activations.

Polarized Induced Magnetic Broadening of Photonic Activities in Fe3O4-Elastomer Composites

AbstractWe report a systematic study of polarization and magnetic field effects on the optical response of Fe3O4-silicone elastomer composite. The Fe3O4 particles were aligned in a silicone elastomer matrix with an external static magnetic field. Films of composites containing 5wt% of 20nm ≤ d ≤ 30nm Fe3O4 particles aligned in- and out-of-plane in the elastomer host were prepared. The optical spectra of the films were measured with the Perkin-Elmer Lambda 950 UV/vis/NIR spectrometer. We observed a systematic redshift in the optical response of the outof-plane composite films with increasing static magnetic field strength, which saturated near 600 Gauss. We obtained a maximum redshift of ∼46 nm at 600 Gauss. The observed redshift in the optical response of the out-of-plane composite film is attributed to the effect of the magnetic field. This facilitated the formation of the highly aligned particles that induced strong electric dipole in the aligned particles. Interestingly, there were no observable shifts with increasing magnetic field strength in the in-plane films, suggesting that the orientation (polarization) of the magnetic dipole and the induced electric dipole play a crucial role in the optical response.

Three Dimensional Model of a High Temperature PEMFC. Study of the Flow Field Effect on Performance

AbstractA three‐dimensional isothermal model of a high temperature polymer membrane fuel cell equipped with polybenzimidazole membrane is described. All major transport phenomena were taken into account except the species crossover through the membrane. The cathode catalyst layer was treated as spherical catalyst agglomerates with porous inter‐agglomerate spaces. The inter‐agglomerate spaces were filled with a mixture of electrolyte (hot phosphoric acid) and polytetrafluoroethylene (PTFE). This approach proved to be an essential requirement for accurate simulation. In this particular paper, the influence of different flow field designs and dimensions on performance was intensely study. Traditional configurations were tested (straight, serpentine, pin‐in, and interdigitated), and new designs were proposed. With these new designs, we tried to maximize performance by providing homogeneous reactants distribution over the active area keeping low‐pressure drop and relatively high velocity. The dimension and position of the inlet and outlet manifolds were also analyzed. From the obtained results a massive influence of the manifolds position and dimension on performance was observed. This fact can provide important guidelines for future bipolar plates optimization.

Room temperature positive magnetoresistance and field effect studies of manganite-based heterostructure

We report the results of studies of rectifying behavior, positive magneoresistance (MR), the charge-transport mechanism and the effect of an electric field on a ZnO (n)/La0.5Pr0.2Sr0.3MnO3 (LPSMO) (p)/SrNb0.002Ti0.998O3 (SNTO) (n) heterostructure comprising two p–n junctions fabricated using the pulsed laser deposition technique. The heterostructure exhibits rectifying behavior over a wide temperature and field range having hysteresis in I–V behavior (forward bias) due to the tunneling of charge carriers. It is also observed that, depending on the nature of the electric field bias to n-type ZnO and SNTO, the junction resistance becomes modified, which has been explained on the basis of spin injection in the heterostructure. The observation of unconventional positive MR at room temperature has been justified on the basis of interface effects and the reduction in barrier height obtained using fitting of the I–V data by a thermionic emission model.

Radical Cations of Branched Alkanes in Solutions: Time-Resolved Magnetic Field Effect and Quantum Chemical Studies

Radical cations of heptane and octane isomers, as well as several longer branched alkanes, were detected in irradiated n-hexane solutions at room temperature by the method of time-resolved magnetic field effect (TR MFE). To identify radical cations, the hyperfine coupling constants as determined by simulation of the TR MFE curves were compared to the constants calculated using the density functional theory (DFT) approach. The g-values of the observed radical cations were close to that of the 2,2,3,3-tetramethylbutane radical cation studied earlier by optically detected electron spin resonance (ESR) and TR MFE techniques. No evidence of the decay of the radical cations of branched alkanes to produce olefin radical cations was found, which was further supported by the observation of positive charge transfer from the observed radical cations to cycloalkane molecules. The lifetimes of the radical cations of the branched alkanes were found to be longer than tens of nanoseconds.

Study of the magnetic field effects on carriers’ mobility in polymer based light-emitting diodes

The magnetic field effects on the carriers’ mobility have been investigated for poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonat) (PFO) based light emitting diodes by the transient electroluminescence (EL) method. The EL pulses can be divided into the following six regions: (a) a delay region; (b) a fast initial rising edge; (c) a second slower rising edge; (d) a quasisteady state; (e) a fast falling edge; and (f) a slow decay region. The effect of the external magnetic field on the different regions can be obtained by measuring the EL pulses both with and without a magnetic field. It is found that the external magnetic field has no effect on both the electron and hole mobility in PFO based light-emitting diodes when the driving voltage is above the onset of the electroluminescence.

The Study of Field Effect through Uniaxial Compression Experiment on Marine Recycled Concrete Specimen Based on DPDM Technique

Recycled concrete is a kind of composite heterogeneous material. Through the uniaxial compression experiment on recycled concrete specimen, the corresponding stress-strain curve is depicted with the major variables of replacement rate of recycled aggregate and time of corrosion by seawater, and the analysis of compression resistance capacity of recycled concrete sample is carried out by comparing common samples with those after the process of vacuum pumping. According to the results of comparison, the process of vacuum pumping can raise the strength of concrete by 9% to 22% and the lowering speed of compression resistance capacity rises as replacement rate of recycled aggregate goes up after the same corrosion period. The compression resistance capacity of the concrete specimen with replacement rate of 60% descends 50% to 80% faster than the sample with 30% of rate. DPDM technique is used to analyze deformation field, displacement field and strain field of concrete specimen during the process of uniaxial compression. As shown in the images from the experiment, the cracks develop from the bottom and both edges towards the middle part along the direction of loading until some of them run through the cube with the failure of the overall specimen while the stress reaches the peak, the displacement amount decreases from bottom to top and from both edges to center and the greatest strain concentration scatters around the bottom of the specimen while the strain of 62% appears around the peak stress of 33-36MPa. This paper puts forward constructive references and guidance for the application of recycled concrete in marine engineering on the basis of the study of field effect through uniaxial compression experiment based on DPDM technique.

The Study of Field Effect through Uniaxial Compression Experiment on Marine Recycled Concrete Specimen Based on DPDM Technique

The Study of Field Effect through Uniaxial Compression Experiment on Marine Recycled Concrete Specimen Based on DPDM Technique

Control of ferromagnetism at room temperature in (Ti,Co)O2−δ via chemical doping of electron carriers

Ferromagnetism at room temperature in (Ti,Co)O2 − δ was controlled by changing its electron density via chemical doping, where the oxygen vacancy δ served as an electron donor. With increasing the electron density, the ferromagnetic anomalous Hall effect and magnetization emerged from a paramagnetic state, while undergoing an insulator to metal transition. This result supports that the electron carriers mediated the ferromagnetic exchange interaction and is consistent with the electric field effect study on the ferromagnetism recently reported [Y. Yamada, K. Ueno, T. Fukumura, H. T. Yuan, H. Shimotani, Y. Iwasa, L. Gu, S. Tsukimoto, Y. Ikuhara, and M. Kawasaki, Science 332, 1065 (2011)].

FTIR and UV spectroscopy in real-time monitoring of S. cerevisiae cell culture

A combination of FTIR and UV spectroscopy is proposed as a novel technique for integrated real-time monitoring of metabolic activity and growth rates of cell cultures, required for systematic studies of cellular low-frequency (LF) electric and magnetic field (EMF) effects. As an example, we investigated simultaneous influence of periodic LF 3D EMFs on a culture of Saccharomyces cerevisiae (baker's yeast) cells. Amplitudes, frequencies and phases of the field components were the variable parameters. Electromagnetic fields were found to efficiently control the activity of the yeast cells, with the resulting CO2 production rates, as monitored by FTIR spectroscopy, varying by at least one order of magnitude due to the field action. Additionally, population dynamics of the yeast cells was monitored by UV absorption of the yeast culture at λprob = 320 nm, and compared to the CO2 production rates. The detected physiologically active frequencies are all below 1 kHz, namely, 800 Hz excitation was effective in reducing the metabolic rates and arresting cell proliferation, whereas 200 Hz excitation was active in accelerating both cell proliferation and overall metabolic rates. The proposed methods produce objective, reliable and quantitative real-time results within minutes and may be used in various tasks that could benefit from a rapid feedback they provide in the form of metabolic and growth rates. Amplitude and frequency dependences of the LF EMF effects from individual field components with different polarizations were recorded and qualitatively interpreted based on a simple model, describing ion diffusion through a membrane channel.