The electrical transport properties of epitaxial graphene layers are correlated with the SiC surface morphology. In this study we show by atomic force microscopy and Raman measurements that morphology structure change significantly when different pretreatment procedures applied to nearly on-axis 6H-SiC(0 0 1) substrates. It turns out often used hydrogen etching substrate is responsible for undesirable high macro-steps evolving during growth. A more advantageous type sub-nanometer stepped...

We study the remanent domain configurations of rectangular permalloy antidot lattices over a range lattice parameters. The influence diameter, spacing, and aspect ratio on configuration are investigated by magnetic force microscopy supported micromagnetic simulations. In state, areas cells with same orientation average magnetization form super domains separated walls (SDWs). Two types SDWs identified. first type is characterized low stray field energy, linear, expands many constants....

The Josephson effect in superconductors links a quantized output voltage Vout = f \cdot(h/2e) to the natural constants of electron's charge e, Planck's constant h, and an excitation frequency with important applications electrical quantum metrology. Also semiconductors are routinely applied metrology making use Hall effect. However, despite their broad range further e.g. integrated circuits, generation by semiconductor device has never been obtained. Here we report source generating voltages...

Precision measurements of the quantum Hall resistance with alternating current (ac) in kHz range were performed on epitaxial graphene order to assess its suitability as a standard impedance. The plateaus measured found be flat within one part 107. This is much better than for plain GaAs devices and shows that magnetic-flux-dependent capacitive ac losses device are less critical. observed frequency dependence about −8 × 10−8/kHz comparable absolute value positive devices, but negative sign...

This paper describes the measurements of ac quantum Hall effect (QHE) in epitaxial graphene a set six different devices. In typical devices, capacitive losses cause negative frequency dependence resistance, contrast to positive observed GaAs one sample, very low dissipation was measured along with resistance decreasing by less than part 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> between 0 and kHz, which demonstrates potential QHE...

We investigate the $1/f$ noise properties of epitaxial graphene devices at low temperatures as a function temperature, current, and magnetic flux density. At currents, an exponential decay power spectral density with increasing temperature is observed that indicates mesoscopic conductance fluctuations origin below 50 K. higher deviations from typical quadratic current dependence occur result nonequilibrium conditions due to heating. By applying Kubakaddi theory [S. S. Kubakaddi, Phys. Rev. B...

Abstract This paper presents the implementation of an electronic fully-digital impedance bridge optimized for RC comparisons with equal magnitudes, together evaluation uncertainty. has been designed goal realizing farad directly from quantum Hall effect a uncertainty component at 10 −7 level. Thanks to its simple design, ease operation and affordability, this is suitable be industrially manufactured. Together increasing availability graphene resistance standards, can provide affordable...

We investigate the application of nanoscale topgates on exfoliated bilayer graphene to define quantum dot devices. At temperatures below 500 mK, conductance underneath grounded gates is suppressed, which we attribute nearest neighbour hopping and strain-induced piezoelectric fields. The gate-layout can thus be used resistive regions by tuning into corresponding temperature range. use this method a structure in showing Coulomb blockade oscillations consistent with gate layout.

The robust and reproducible formation of a quantum dot is key for the development tunable barrier single-electron pumps as future current standard. We investigate fabrication process perform electrical characterizations at cryogenic temperatures dots realized in GaAs/AlGaAs heterostructure with lateral potential confinement by combination shallow-etch technique metallic top-gates. Stable geometric parameters lithography (5% deviation) homogeneous resulted 37 out 39 tested devices.

We report a novel, sputtering-based fabrication method of Al2O3 gate insulators on graphene. Electrical performance dual-gated mono- and bilayer exfoliated graphene devices is presented. Sputtered layers possess comparable quality to oxides obtained by atomic layer deposition with respect high relative dielectric constant about 8, as well low-hysteresis breakdown voltage. observe moderate carrier mobility 1000 cm2 V−1 s−1 in monolayer 350 graphene, respectively. The decrease can be...

We numerically and experimentally investigate the influence of single defects consisting a missing antidot on spin configurations in rectangular permalloy lattices. The introduction such lattice leads to nucleation complex domain structures after decay saturating magnetic field. Micromagnetic simulations yield four typical around defect having distinct energy densities. existence is confirmed by force microscopy lattices containing individual defects.

We investigate the properties of magnetocapacitance and dissipation factor epitaxial graphene Hall bars with different electrode configurations to gain insight into underlying physical mechanisms. The dependence on magnetic field shows how screening ability two-dimensional electron gas (2DEG) changes at transition from nonquantized quantized state. Both exhibit a characteristic correlated voltage dependence, which is attributed alternating contraction expansion nonscreening 2DEG regions due...

Graphene is a native one-atom-thick crystal consisting of single sheet carbon atoms. In this material, discovered in 2005, the electron transport ballistic at room temperature and described by relativistic-like quantum Dirac equation instead Schrodinger equation. Also, graphene has Young modulus 1.5 TPa. Due to these unique properties, very promising for high frequency nanoelectronic devices, such as oscillators switches. paper, we show that barrier switch with on-off ratio, which large...

We study the precession frequency and effective damping of patterned permalloy thin films different geometry using integrated inductive test structures. The structures consist coplanar wave guides fabricated onto stripes geometry. width, length position stripe with respect to center conductor guide are varied. devices is derived by measurements in time domain in-plane magnetic fields. While frequencies do not reveal a significant dependence on sample we find decrease measured increasing...

Inductance standards currently available are made up of toroidal inductors, i.e., coils wire wound around a nonmagnetic core. The maximum inductance achievable is 10 H, while modern LCR meters offer measurement ranges to more than kH. Due their winding capacitance and resistance, inductors exhibit quite large parasitic elements that restrict the operating frequency due resonances. Using gyrator in conjunction with standard creates synthesized inductance, which can values hundreds...

Inductance standards currently available are made up of toroidal inductors, i.e. coils wire wound around a non-magnetic core. The maximum inductance achievable is 10 H, while modern LCR meters offer measurement ranges to more than kH. Due their winding capacitance and resistance, inductors exhibit quite large parasitic elements that restrict the operating frequency due resonances. Using gyrator in conjunction with standard creates synthesized which can values hundred kilohenrys. Optimizing...

This paper describes measurements of the AC quantum Hall resistance in epitaxial graphene performed with a newly developed digitally assisted impedance bridge. Capacitive losses cause negative frequency dependence resistance, contrast to positive observed GaAs devices. The magnitude varies among individual samples and can be significantly larger than

Quantum Hall resistors made from epitaxial graphene measured with alternating current exhibit an unusual negative frequency dependence. To test the hypothesis that parasitic capacitances between contact pads cause this effect, we studied capacitance and dissipation factor in quantum regime for various in-plane electrode configurations. The largest is found configurations where a strong electric field penetrates bulk of graphene. effect different on dependence quantized resistance confirms...

We report measurements of the magneto-capacitance and associated dissipation factor graphene-based quantum Hall effect devices at frequencies in kHz range. The main motivation for this work is yielding information modeling optimization resistance measured with alternating current, but here we focus on characteristic ac properties graphene relevant loss mechanism.

AC-DC transfer is performed almost exclusively using thermal converters. At voltages above a few volts, series resistors are used to extend the permissible voltage, which leads significant power being drained from source. By contrast, sensing electrical field in suitable electrode system by utilizing Pockels effect of an electrooptic crystal will draw just small, only capacitive current. The impact analyzed detecting rotation polarization light beam means analyzing polarizer and photo...