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The magnetoconductivity in anisotropic Corbino geometry has been studied experimentally and theoretically. The magnetoconductivity curve σrr(B) follows the average magnetoconductivity σar(B) = (σxx(B) + σyy(B))/2 in classically strong magnetic fields. In the region of classically weak magnetic fields, σrr(B) goes below σar(B). A theoretical study of anisotropic Corbino disk (ACD) magnetoconductivity has been carried out using the classical description of transport based on the calculation of current streamlines. The expressions for calculating the ACD magnetoconductivity for an arbitrary degree of anisotropy have been obtained. In the region of fields B > 1/μ, where μ is the mobility, the calculation results are in good agreement with the experiment. In the fields B < 1/μ, we have not been able to compare the calculations with the experiment because of using samples with too high mobility and a simple two-point measurement scheme. Our calculations allow us to estimate the value of deviation of the ACD magnetoconductivity from the average magnetoconductivity in a weak magnetic field. [ABSTRACT FROM AUTHOR]

We investigate the magnetoresistance (MR) effect in n-doped InAs and InAs/metal hybrid devices with geometries tailored to elucidate the physical mechanism and the role of geometry in the MR. Despite the isotropic Fermi surface in InAs, we observe a strong intrinsic MR in the InAs epilayer due to the existence of a surface conducting layer. Experimental comparison confirms that the extraordinary MR in the InAs/metal hybrids outperforms the orbital MR in the Corbino disk in terms of both the MR ratio and the magnetic field resolution. The results also indicate the advantage of a two-contact configuration in the hybrid devices over a four-contact one with respect to the magnetic field resolution. This is in contrast to previously reported results, where performance was evaluated in terms of the MR ratio and a four-contact configuration was found to be optimal. By applying Kohler's rule, we find that at temperatures above 75 K the extraordinary MR violates Kohler's rule, due to multiple relaxation rates, whereas the orbital MR obeys it. This finding can be used to distinguish the two geometric effects, the extraordinary MR and the orbital MR, from each other. [ABSTRACT FROM AUTHOR]

We present here polarization operator of non-relativistic fermions with spin-orbit (SO) Rashba interaction. The spectrum of this fermions is moat type having minimum on a circle. Contrary to Dirac or non-relativistic fermions, Fermi sea here has a geometry of Corbino disk which reflects in a transport properties of excitation's. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the influence of magnetic field on 1/ f noise in gallium arsenide Corbino disks. Method of the study; Results and discussion; Conclusion.

We solve Dirac-Bogoliubov-De-Gennes (DBdG) equation in a superconductor-normal graphene-superconductor (SGS) junction with Corbino disk structure to investigate the Josephson current through this junction. We find that the critical current I c has a nonzero value at Dirac point in which the concentration of the carriers is zero. We show this nonzero critical current depends on the system geometry and it decreases monotonically to zero by decreasing the ratio of the inner to outer radii of the Corbino disk ( R 1 / R 2 ), while in the limit of R 1 / R 2 → 1 it scales like a diffusive Corbino disk. The product of the critical current and the normal-state resistance I c R N increases by increasing R 1 / R 2 and attains the same value for the wide and short rectangular structure at the limit of R 1 / R 2 → 1 at zero doping. These results reveals the pseudodiffusive behavior of the graphene Corbino Josephson junction similar to the rectangular structure at the zero doping. [ABSTRACT FROM AUTHOR]

We discuss the non-equilibrium properties of integer channels in nonuniform 2D electron (hole) systems in the presence of a strong magnetic field. The results are applied to a qualitative explanation of the Corbino disk current-voltage characteristics (IVC) in the quantum Hall effect (QHE) regime. Special consideration is paid to the so-called “QHE breakdown” effect, which is readily observed in both the Hall bar and Corbino geometries of the tested cells. The QHE breakdown is especially evident in the Corbino samples, allowing for a more in-depth study of these effects. [ABSTRACT FROM AUTHOR]

Among the various geometries to study the fractional quantum Hall effect in two dimensional electron gas, the Corbino disc owns the advantage to probe the bulk properties directly. In this work we explore the influence of in-plane electric fields on the stability of the 5/2 fractional quantum Hall state realized in Corbino geometry. The effect of weak electric fields is investigated at ultra-low temperatures in order to compare with a theoretical proposal of enhanced Pfaffian state under weak electric fields. [ABSTRACT FROM AUTHOR]

We investigated the electrical properties and stability of short-channel half-Corbino amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs). In the linear region, the fabricated half-Corbino a-IGZO TFT with a channel length of 4.5 μm achieves a geometrical factor ( f g ) of ∼2.7, a threshold voltage ( V T ) of ∼2.4 V, a field-effect mobility ( μ eff ) of ∼15 cm 2 /Vs, a subthreshold swing ( SS ) of ∼320 mV/dec and an off-current ( I OFF ) < 10 −13 A. In the saturation region, asymmetric electrical characteristics such as drain current were observed under different drain bias conditions. The electrical properties asymmetry of half-Corbino a-IGZO TFTs was explained by various geometrical factors owing to the short-channel effect. The reduced V T and increased SS at V DS = 15 V is explained by the drain-induced Schottky barrier lowering. In addition, the bias-temperature stress (BTS) was performed for half-Corbino a-IGZO TFTs with both amorphous silicon oxide (a-SiO x ) single layer and a-SiO x /amorphous silicon nitride (a-SiN x ) bilayer passivation (PV) structures. The device with bilayer PV shows a threshold voltage shift (Δ V T ) of +2.07 and −0.5 V under positive (PBTS = +15 V) and negative BTS (NBTS = −15 V) at 70 °C for 10 ks, respectively. The origins of Δ V T during PBTS and NBTS for half-Corbino a-IGZO TFTs with single and bilayer PV structures were studied. To improve the device electrical stability, the bilayer PV structure should be used. [ABSTRACT FROM AUTHOR]

Given the infinite output resistance exhibited by Corhino TFTs beyond pinch-off, uniform OLED cutrent is maintained, even in large-area displays, where supply-voltage (Vod) way vary due to IR drop. Here we extend their application to flexible A MOLED displays, where their circular shape provides excellent stability against self-heating and mechanical bending-sfrain. [ABSTRACT FROM AUTHOR]

We examine theoretically the dynamics of two vortex shells in pinning-free superconducting thin disks in the Corbino geometry. In the first considered case, the inner shell is composed of vortices and the outer one of antivortices, corresponding to a state induced by the stray field of an off-plane magnetic dipole placed on top of the superconductor. In the second considered case, both shells comprise vortices induced by a homogeneous external field. We derive the equation of motion for each shell within the Bardeen-Stephen model and study the dynamics analytically by assuming both shells are rigid and commensurate. In both cases, two distinct regimes for vortex shell motion are identified: For low applied currents the entire configuration rotates rigidly, while above a threshold current the shells decouple from each other and rotate at different angular velocities. Analytical expressions for the decoupling current, the recombination time in the decoupled phases, as well as the voltage-current characteristics are presented. Our analytical results are in excellent agreement with numerical molecular dynamics simulations of the full many-vortex problem. [ABSTRACT FROM AUTHOR]

This is a discussion of the details of the current-voltage characteristics of a 2D Corbino disk with a uniform density of mobile carriers in the quantum Hall effect plateau. It is shown that diffusion may be one of the reasons for the variety of observed current-voltage characteristics. The anomalous role of diffusion in the formation of the current-voltage characteristics of Corbino disks is determined by the dimensionality of the problem, as well as by the "quality" of the density of states of the magnetized 2D conducting system. The diffusion hypothesis is applied to some specific results and provides an explanation of the difference between the current-voltage characteristics shown in Figs. 1 and 2. [ABSTRACT FROM AUTHOR]

A phase from an adiabatic exchange of Majorana bound states (MBS) reveals their exotic anyonic nature. For detecting this exchange phase, we propose an experimental setup consisting of a Corbino geometry Josephson junction on the surface of a topological insulator, in which two MBS at zero energy can be created and rotated. We find that if a metallic tip is weakly coupled to a point on the junction, the time-averaged differential conductance of the tip-Majorana coupling shows peaks at the tip voltages eV=±(α-2πl)ħ/TJ, where α=π/2 is the exchange phase of the two circulating MBS, TJ is the half rotation time of MBS, and l an integer. This result constitutes a clear experimental signature of Majorana fermion exchange. [ABSTRACT FROM AUTHOR]

The recent conjecture of a topologically protected surface state in SmB6 and the verification of robust surface conduction below 4 K have prompted a large effort to understand surface states. Conventional Hall transport measurements allow current to flow on all surfaces of a topological insulator, so such measurements are influenced by contributions from multiple surfaces of varying transport character. Instead, we study magnetotransport of SmB6 using a Corbino geometry, which can directly measure the conductivity of a single, independent surface. Both (011) and (001) crystal surfaces show a strong negative magnetoresistance at all magnetic field angles measured. The (011) surface has a carrier mobility of 122 cm²/V. s with a carrier density of 2.5 x 1013 cm-2, which are significantly lower than indicated by Hall transport studies. This mobility value can explain the failure so far to observe Shubnikov-de Haas oscillations. Analysis of the angle dependence of conductivity on the (011) surface suggests a combination of a field-dependent enhancement of the carrier density and a suppression of Kondo scattering from native oxide layer magnetic moments as the likely origin of the negative magnetoresistance. Our results also reveal a hysteretic behavior whose magnitude depends on the magnetic field sweep rate and temperature. Although this feature becomes smaller when the field sweep is slower, it does not disappear or saturate during our slowest sweep-rate measurements, which is much slower than a typical magnetotransport trace. These observations cannot be explained by quantum interference corrections such as weak antilocalization but are more likely due to an extrinsic magnetic effect such as the magnetocaloric effect or glassy ordering. [ABSTRACT FROM AUTHOR]

For certain measurements, the Corbino geometry has a distinct advantage over the Hall and van der Pauw geometries, in that it provides a direct probe of the bulk 2DEG without complications due to edge effects. This may be important in enabling detection of the non-Abelian entropy of the 5/2 fractional quantum Hall state via bulk thermodynamic measurements. We report the successful fabrication and measurement of a Corbino-geometry sample in an ultra-high mobility GaAs heterostructure, with a focus on transport in the second and higher Landau levels. In particular, we report activation energy gaps of fractional quantum Hall states, with all edge effects ruled out, and extrapolate σ 0 from the Arrhenius fits. Our results show that activated transport in the second Landau level remains poorly understood. The development of this Corbino device opens the possibility to study the bulk of the 5/2 state using techniques not possible in other geometries. [ABSTRACT FROM AUTHOR]

We investigate a single-electron tunneling effect of two-dimensional electron systems formed in the Corbino nano-scale disk. By controlling bias and gate voltages, the transistor using this effect is able to control electrons one by one. The present study focuses on the electronic transmission probability affected by the charging energy in the Corbino-type single-electron transistor. We reformulated the Schrödinger equation for an electron in the Corbino disk in order to consider the effect of the curvature of the disk, taking into account the charging effect on the performance of the Corbino-type single-electron transistor. We formulated the transmission probability of the electron by applying the Wentzel-Kramers-Brillouin (WKB) method. The electron's energy in the formula of the transmission probability is then associated to the energy eigenvalue of the Schrödinger equation for an electron in an effective confining potential. We numerically solved the Schrödinger equation to evaluate the transmission probability. Our results show that the transmission probability strongly depends on the charging energy stored in the Corbino disk depending on its size. [ABSTRACT FROM AUTHOR]

A high-gain source follower, utilizing oxide TFTs with a Corbino (circular) structure, is reported. Given the infinite output resistance exhibited by Corbino TFTs in the outer-drain condition (i.e., when the outer electrode is biased as the drain), the Corbino TFT-based source follower provides higher gain in operation than its rectangular TFT-based counterparts. [ABSTRACT FROM AUTHOR]

In the higher Landau levels (N > 0) a reentrant integer quantum Hall effect (RIQHE) state, which resides at fractional filling factors but exhibits integer Hall plateaus, has been previously observed and studied extensively. The nonlinear dynamics of the RIQHE were measured by microwave resonance, with the results consistent with an electronic bubble phase pinned by impurities. We have carried out depinning experiments on the N = 2 bubble phases by using Corbino geometry, where depinning threshold values have been systematically measured as a function of magnetic fields and temperatures. Domain sizes and pinning potential of the bubble phases have been estimated from the nonlinear transport data. [ABSTRACT FROM AUTHOR]

Bulk and surface state contributions to the electrical resistance of single-crystal samples of the topological Kondo-insulator compound SmB6 are investigated as a function of crystal thickness and surface charge density, the latter tuned by ionic liquid gating with electrodes patterned in a Corbino disk geometry on a single (100) surface. By separately tuning bulk and surface conduction channels, we show conclusive evidence for a model with an insulating bulk and metallic surface states, with a crossover temperature that depends solely on the relative contributions of each conduction channel. The surface conductance, on the order of 100 e2/h , exhibits a field-effect mobility of 133 cm2/Vs and a large carrier density of ∼2 x 1014 cm-2, in good agreement with recent photoemission results. With the ability to gate modulate surface conduction by more than 25%, this approach provides promise for both fundamental and applied studies of gate-tuned devices structured on bulk crystal samples. [ABSTRACT FROM AUTHOR]

We have observed electrical-field induced magneto-conductivity oscillations measured in Corbino samples made of a GaAs high-mobility two-dimensional electron gas, and found a consistent interpretation based on a semiclassical model of 2kF-selected orbital transitions between N and N + 1, 2, 3,..., Landau levels at respective local potentials, where kF is the Fermi wavevector. From the oscillation period, we deduce an effective mass value, which is consistent with the bare electron band mass of GaAs. In the same devices but with a vanishing electrical field and at elevated temperatures, we observed additional oscillation features, which can be attributed to cyclotron resonance by population of acoustic phonons. We thus demonstrate a method to determine the carrier effective mass and the sound velocity of host crystals by standard electrical transport. [ABSTRACT FROM AUTHOR]

We present the technical details of a broadband microwave spectrometer for measuring the complex conductance of thin films covering the range from 50 MHz up to 16 GHz in the temperature range 300 mK-6 K and at applied magnetic fields up to 8 T. We measure the complex reflection from a sample terminating a coaxial transmission line and calibrate the signals with three standards with known reflection coefficients. Thermal isolation of the heat load from the inner conductor is accomplished by including a section of NbTi superconducting cable (transition temperature around 8-9 K) and hermetic seal glass bead adapters. This enables us to stabilize the base temperature of the sample stage at 300 mK. However, the inclusion of this superconducting cable complicates the calibration procedure. We document the effects of the superconducting cable on our calibration procedure and the effects of applied magnetic fields and how we control the temperature with great repeatability for each measurement. We have successfully extracted reliable data in this frequency, temperature, and field range for thin superconducting films and highly resistive graphene samples. [ABSTRACT FROM AUTHOR]

We have measured the current noise in a device with Corbino geometry to investigate the dynamics of electrons in the breakdown regime of the integer quantum Hall effect (QHE). In the breakdown regime, the Fano factor of the current noise exceeds 103, which indicates the presence of electron bunching. As super-Poissonian current noise is observed only in the breakdown regime, the bunching effect is related to the QHE breakdown. These observations support a QHE breakdown mechanism that involves an electron avalanche. [ABSTRACT FROM AUTHOR]

The use of a Corbino thin-film transistor (TFT) as the driving-TFT in large-area active-matrix organic light-emitting diode (AMOLED) display pixels is reported. Given the infinite output resistance exhibited by the Corbino TFT beyond pinch-off, the same drive (diode) currents are maintained, even with voltage (IR) drop-related variations in the supply voltage (VDD). [ABSTRACT FROM AUTHOR]

Presented are OTFT arrays fabricated from a high mobility organic semiconductor ink wherein the preferred TFTs are corbino-type devices. As a direct consequence of the corbino design, the resulting TFTs have very high on/off ratios, typically > 107 coupled with very low off currents. This corbino approach demonstrates that high mobility OTFTs with superior switching ratios can be obtained without the need for isolation of the organic semiconductor. Hansen solubility parameters and mobility data are reported. This also indicates potential for the commercial use of organic semiconductor materials in the industrial production of OTFT backplanes for flexible AMOLED displays. [ABSTRACT FROM AUTHOR]

The scaling behavior of graphene devices in Corbino geometry was investigated through temperature dependent conductivity measurements under magnetic field. Evaluation of the Landau level width as a function of temperature yielded a relatively low temperature exponent of k = 0.16 ± 0.05. Furthermore, an unusually large value close to 7.6 ± 0.9 was found for the universal scaling constant c, while the determined inelastic scattering exponent of p = 2 is consistent with established scattering mechanisms in graphene. The deviation of the scaling parameters from values characteristic of conventional two-dimensional electron gases is attributed to an inhomogeneous charge carrier distribution in the Corbino devices. Direct evidence for the presence of the latter could be gained by spatially resolved photocurrent microscopy away from the charge neutrality point of the devices. [ABSTRACT FROM AUTHOR]

A geometry-independent effective model for the contact self-energies is proposed to calculate the quantum conductance of patterned graphene devices using Green's functions. A Corbino disk, being the simplest device where the contacts cannot be modeled as semi-infinite ribbons, is chosen to illustrate this approach. This system's symmetry allows an analytical solution against which numerical calculations on the lattice can be benchmarked. The effective model perfectly describes the conductance of Corbino disks at low-to-moderate energies, and is robust against the size of the annular device region, the number of atoms on the edge, external magnetic fields, or electronic disorder. The contact model considered here affords an expedient, flexible, and geometry-agnostic approach that easily allows the consideration of device dimensions encompassing several million atoms, and realistic radial dimensions of a few hundreds of nanometers [ABSTRACT FROM AUTHOR]

In this paper, we report on a microwave characterization of the interface between Ti/Au contacts and chemical vapor deposition graphene using structures of Corbino geometry, with primary focus on extracting and modeling the capacitance associated with the contact region. It is found that with the current contact resistivity, ρc∼10-6 Ωcm2, the contact capacitance, on the order Cc∼1 μF/cm2, has a negligible effect on microwave transmission through the contact below ∼100 GHz. Finally, a parallel plate capacitance model for the contact is presented. [ABSTRACT FROM AUTHOR]

The magnetotransport characteristics of quasi-two-dimensional electronic Corbino disks based on a wide GaAs quantum well with two filled subbands of size quantization are studied. At low temperatures and high magnetic fields, the Corbino disks exhibit the oscillations of differential conductivity, which are periodic with respect to dc electric field E. It is shown that the observed oscillations are related to the Zener tunneling induced by E. The tunneling occurs between the filled and empty Landau levels under conditions corresponding to the absence of the Hall field. [ABSTRACT FROM AUTHOR]

This is an analytical study of magnetic fields effects on the conductance, the shot noise power, and the third charge-transfer cumulant for the Aharonov-Bohm rings and the Corbino disks in graphene. The two distinct physical mechanisms lead to very similar magnetotransport behaviors. Differences are unveiled when discussing the third-cumulant dependence on magnetic fields. [ABSTRACT FROM AUTHOR]

A broadband microwave spectrometer has been constructed to determine the complex conductivity of thin metal films at frequencies from 45 MHz to 20 GHz working in the temperature range from 0.45 K to 2 K (in a 3He cryostat). The setup follows the Corbino approach: a vector network analyzer measures the complex reflection coefficient of a microwave signal hitting the sample as termination of a coaxial transmission line. As the calibration of the setup limits the achievable resolution, we discuss the sources of error hampering different types of calibration. Test measurements of the complex conductivity of a heavy-fermion material demonstrate the applicability of the calibration procedures. [ABSTRACT FROM AUTHOR]

The resistance of dual-gated bilayer graphene is measured as a function of temperature and gating electric fields in the Corbino geometry which precludes edge transport. The temperature-dependent resistance is quantitatively described by a two-channel conductance model including parallel thermal activation and variable range hopping channels, which gives the electric-field-dependent band gap whose magnitude is found to be in good agreement with infrared absorption experiments. Low-temperature transport is similar to that seen in previous studies of dual-gated bilayer graphene with edges, suggesting that edge transport does not play an important role. [ABSTRACT FROM AUTHOR]

• A circular Hall disk with a point-like source in the center and and three contacts on the boundary. • A multivalued electrostatic potential for the point source. • Solution of the modified boundary-value problem for the Hall sensor with a point source at the center of the disk. • Optimization of the boundary contacts for the Hall voltage. • Comparison with the Hall disk with four contacts on the boundary. The paper presents an analytical theory for a disk-shaped Hall plate having three peripheral contacts and a point contact at the center. The central contact is modeled as a Corbino source. Its potential function contains a multivalued function. On the boundary, besides the exit contact, the positions of the other two (sensing) contacts were determined in such a way as to maximize the Hall voltage. The numerical results show that, in the case of this type of sensing element (referred to as the Hall-Corbino element), the Hall voltage is more than six times larger than that corresponding to a Hall disk having only peripheral contacts. [ABSTRACT FROM AUTHOR]

Abstract: We use a novel broadband microwave spectroscopy measurement to study the source–drain current characteristics of a GaAs quantum point contact (QPC) within the tunnelling regime. The experimental setup was based on the Corbino approach with the notable difference that it was non-invasive to the sample and swept a frequency range between 1 and 10GHz at low temperatures. Highly aperiodic but completely reproducible conductance fluctuations were observed close to pinch-off as well as regions of negative conductance. We account these fluctuations to be due to quantum interference of ballistic electron trajectories, trapped within the QPC, being modified by the radiation source and influencing the tunnelling rates through a complex potential well structure. [Copyright &y& Elsevier]

Abstract: Recently a one-dimensional closed ladder of Josephson junctions has been studied [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Phys. Lett. A 372 (2008) 2464] within a twisted conformal field theory (CFT) approach [G. Cristofano, G. Maiella, V. Marotta, Mod. Phys. Lett. A 15 (2000) 1679; G. Cristofano, G. Maiella, V. Marotta, G. Niccoli, Nucl. Phys. B 641 (2002) 547] and shown to develop the phenomenon of flux fractionalization [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Eur. Phys. J. B 49 (2006) 83]. That led us to predict the emergence of a topological order in such a system [G. Cristofano, V. Marotta, A. Naddeo, J. Stat. Mech.: Theory Exp. (2005) P03006]. In this Letter we analyze the ground states and the topological properties of fully frustrated Josephson junction arrays (JJA) arranged in a Corbino disk geometry for a variety of boundary conditions. In particular minimal configurations of fully frustrated JJA are considered and shown to exhibit the properties needed in order to build up a solid state qubit, protected from decoherence. The stability and transformation properties of the ground states of the JJA under adiabatic magnetic flux changes are analyzed in detail in order to provide a tool for the manipulation of the proposed qubit. [Copyright &y& Elsevier]

We have developed a picovoltmeter using a Nb dc superconducting quantum interference device for measuring the flux-flow voltage from a small number of vortices moving through a submicron weak-pinning superconducting channel. We have applied this picovoltmeter to measure the vortex response in a single channel arranged in a circle on a Corbino disk geometry. The circular channel allows the vortices to follow closed orbits without encountering any sample edges, thus eliminating the influence of entry barriers. [ABSTRACT FROM AUTHOR]

The microwave photoconductivity of the 2D electron gas in GaAs/AlAs heterostructures has been investigated at a temperature of 4.2 K in magnetic fields up to 1.5 T. It has been found that the magnetic field state with zero conductivity appears in GaAs/AlAs Corbino disks irradiated by 130.70-GHz microwave radiation. This state was previously observed only in GaAs/AlGaAs Corbino disks with much higher electron mobility and lower density. It has been shown that the microwave photoconductivity measured in high magnetic fields on Corbino disks can significantly differ from the value calculated from the results of the measurements on Hall bars. This difference is explained by the fact that the conditions of the appearing magnetoplasmons that affect the magnitude and character of the microwave photoconductivity (photoresistance) in the Corbino disks are nonequivalent to those in the Hall bars. [ABSTRACT FROM AUTHOR]

We present a high-resolution microwave spectrometer to measure the frequency- dependent complex conductivity of a superconducting thin film near the critical temperature. The instrument is based on a broadband measurement of the complex reflection coefficient, S11, of a coaxial transmission line, which is terminated to a thin film sample with the electrodes in a Corbino disk shape. In the vicinity of the critical temperature, the standard calibration technique using three known standards fails to extract the strong frequency dependence of the complex conductivity induced by the superconducting fluctuations. This is because a small unexpected difference between the phase parts of S11 for a short and load standards gives rise to a large error in the detailed frequency dependence of the complex conductivity near the superconducting transition. We demonstrate that a new calibration procedure using the normal-state conductivity of a sample as a load standard resolves this difficulty. The high quality performance of this spectrometer, which covers the frequency range between 0.1 and 10 GHz, the temperature range down to 10 K, and the magnetic field range up to 1 T, is illustrated by the experimental results on several thin films of both conventional and high temperature superconductors. [ABSTRACT FROM AUTHOR]

Inverted stagger hydrogenated-amorphous-silicon (a-Si:H) Corbino thin-film transistors (TFTs) were fabricated with a five-photomask process used in the processing of the active-matrix liquid-crystal displays (AM-LCD). We show that the a-Si:H Corbino TFT has the asymmetric electrical characteristics under different drain-bias conditions. To accommodate for these differences when the electrical device parameters are extracted, we developed asymmetric geometric factors. The ON-OFF current ratio can be significantly enhanced by choosing the outer electrode as the drain, while the field-effect mobility and threshold voltage are identical when different drain-bias conditions are used. Finally, we developed concepts of its possible application to AM-LCDs and active-matrix organic light-emitting displays. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the vortex dynamics driven by the constant current I in the Meissner phase of a thick amorphous Mo x Si1−x film with the Corbino-disk contact geometry. In the certain I region we have observed unusual large voltage pulses that oscillate almost periodically with a period t 0 larger than ∼15 s and with the pulse width t w in the range 5–10s. With increasing I, t 0 initially decreases and then increases. Over the whole I region where the oscillation of V(t) is observed, both t 0 and t w are much longer than the characteristic time for free vortices to rotate in the circles. At high I a small peak(s) or cusp-like structure exceeding the normal-state voltage appears on the top (plateau) region of the pulses. These results indicate that the observed voltage pulses originate from large vortex-density fluctuations of moving vortices. [Copyright &y& Elsevier]

We use a quasi-Corbino sample geometry with independent contacts to different edge states in the quantum Hall effect regime to investigate a charge redistribution between cyclotron-split edge states at high imbalance. We also modify the Büttiker formalism by introducing local transport characteristics in it and use this modified Büttiker picture to describe the experimental results. We find that charge transfer between cyclotron-split edge states at high imbalance can be described by a single parameter, which is a transferred between edge states portion of the available for transfer part of the electrochemical potential imbalance. This parameter is found to be independent of the particular sample characteristics, describing fundamental properties of the interedge-state scattering. From the experiment we obtain it in the dependence on the voltage imbalance between edge states and propose a qualitative explanation to the experimental findings. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The dynamics of inhomogeneous current flow in a Corbino sample geometry under a perpendicular magnetic field has been studied using a nonlinear generation–recombination model of conducting electrons. A spontaneous symmetry-breaking development of high electron density streamers rotating in a Hall field has been found, preceding the formation of experimentally observable current filaments. [Copyright &y& Elsevier]

Modification of the theory describing the current-voltage characteristics of the shielded Corbino disk with spinless two-dimensional (2D) electron system under a magnetic field for nearly integer filling factors in the case of a weak pulling electric field (i.e., its energy being much lower than the cyclotron energy) is suggested. Features of the I-V characteristics in the limits of "pure" and "dirty" 2D electron system are considered. The results are compared with experimental data. Local parameters characterizing the disk with flowing current that can be measured via a linear electrooptical effect (distribution of the 2D electron density, and electric and electrochemical potentials) are determined. [ABSTRACT FROM AUTHOR]

Discusses a study which presented a fully inductive method for measuring the internal capacitance of a Corbino ring in the quantum Hall resistance (QHR). Experimental set up of the study; Measurement of the real and imaginary components of the voltage; Conclusion.

Unusual oscillations of the conductivity of a two-dimensional Corbino disk in a magnetic field, which were recently observed experimentally, are discussed on the basis of existing ideas about the specific properties of the contacts of a two-dimensional electronic system with "external" metallic electrodes. [ABSTRACT FROM AUTHOR]

It is shown that the characteristic features of the chemical potential for 2D electrons in a magnetic field, which lead to sharp dips in the magnetic field dependence of the capacitance of a 2D system, also affect the electrostatic potential distribution in the direction of the transport current flowing through a 2D Corbino disk under conditions of integral magnetic filling factor. The associated details of the temperature dependence of the electrostatic potential distribution, the distances to the screening electron, and the transport potential difference at the Corbino edges are investigated. The possibilities of experimentally observing these features of the electrostatic potential distribution along a Corbino disk with a transport current under conditions of the quantum Hall effect are discussed. © 1997 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Corbino effect is calculated for concentric cylindrical semiconductor devices which operate under double- and single-injection. For the two carrier structures, the I-V characteristics are represented by an Proportional toV relationship where = (1+pn B)/[1+(B)][1+(B)] and n=2 for the semiconductor regime and n=3 for the insulator regime.
Similar results are obtained for single-injection space-charge-limited current where n=2 and =[1+(B)].
The present paper describes the effects of a transverse magnetic field on the I-V relationships of double- and single-injection structures which have a concentric cylindrical geometry. The device configuration is a hollow-core coaxial semiconductor with carrier injecting contacts at the inner and outer surfaces of the annulus. At low-injection levels, the I-V relationships are linear and a magnetic field applied perpendicular to the radial direction causes the charge carriers to follow spiral path-lengths between the inner and peripheral contacts (Corbino 1911).
As the injection levels are increased, the I-V relationships are no longer linear because the excess carriers injected into the concentric cylindrical semiconductor lead to various double- and single-injection phenomena. The main purpose is to obtain an estimate of the influence of a magnetic field on the I-V characteristics of annular structures which operate under these high-level injection conditions. [ABSTRACT FROM AUTHOR]

Abstract: We study the rectification of vortex motion in an asymmetric ring channel in a Corbino setup. With an applied ac current, the motion of vortices in the channel is rectified by the asymmetric potential and induces a dc net flow. The net flow in such a system strongly depends on vortex density, and we distinguish “single-vortex” rectification regime (for low density, when each vortex is rectified individually) determined by the potential-energy landscape inside each cell of the channel and “multi-vortex”, or “collective”, rectification (high density case) when the interaction between vortices becomes important. [Copyright &y& Elsevier]

Propagating between the contacts of a field-effect transistor (FET), plasma waves in its channel can become unstable and lead to generation of terahertz radiation. While previous studies of this instability concentrated on rectangular FETs, alternative geometries present fresh opportunities. We studied theoretically plasma oscillations in a gated FET with Corbino geometry where, in contrast with the rectangular FET, the oscillations become unstable at symmetric boundary conditions. Moreover, their lowest eigenfrequency is almost twice as high as that in the rectangular FET at comparable instability increments. These advantages make the Corbino FET promising for practical realizations of terahertz oscillators. [ABSTRACT FROM AUTHOR]