Current-voltage characteristics of Au~/~YBa$_2$Cu$_3$O$_{7-δ}$ interfaces (Au/YBCO), built on optimally-doped YBCO thin films, grown by pulsed laser deposition, were measured as a function of temperature in the 50 K to 270 K range, for two different resistance states. A non-trivial equivalent circuit model is proposed, which reveals the existence of a highly inhomogeneous scenario composed by two complex layers: one presenting both a non-linear Poole-Frenkel conduction as well as Variable Range Hopping localization effects (probably associated with YBa$_2$Cu$_3$O$_{6}$) mixed with a minor metallic phase, while the other is also composed by a mixture of YBCO with different oxygen contents, where a metallic ohmic phase still percolates. A microscopic description of the effects produced by the resistance switching is given, showing the evolution of carrier traps, localization effects and dielectric behavior for each state. The dielectric behavior is interpreted in terms of a Maxwell-Wagner scenario.
Samples of superconducting composite (100-x)YBa2Cu3O7-δ + xNi (x = 1, 2.5, 5, 7.5, 10 and 15 wt.%) were synthesized. Scanning electron microscope (SEM) images revealed that the grain size of YBCO reduces gradually as Ni content is increased. At the same time segregation of Ni as NiO in patches forms throughout the composite. At low Ni wt.%, it was found that the superconducting state properties improved and then dropped with higher Ni wt.%. Segregated patches of NiO on different length scales were observed. The change in the structural and superconducting state parameters of YBCO and the varia…
The observed temperature dependence of electrical conduction in polymer electrolytes is usually fitted with two separated equations: an Arrhenius equation at low temperatures and Vogel-Tamman-Fulcher (VTF) at high temperatures. We report here a derivation of a single equation to explain the variation of electrical conduction in polymer electrolytes at all temperature ranges. Our single equation is in agreement with the experimental data
10 MeV proton-irradiation effects on a YBCO-based test structure were analyzed by measuring its current-voltage (IV) characteristics for different cumulated fluences. For fluences of up to $\sim$80$\cdot$10$^9$~p/cm$^2$ no changes in the electrical behavior of the device were observed, while for a fluence of $\sim$~300$\cdot$10$^9~$ p/cm$^2$ it becomes less conducting. A detailed analysis of the room temperature IV characteristics based on the $γ$ power exponent parameter [$γ=dLn(I)/dLn(V)$] allowed us to reveal the main conduction mechanisms as well as to establish the equivalent circuit mode…
The La0.7Sr0.3MnO3 (LSMO) layers and YBa2Cu3O7-δ/La0.7Sr0.3MnO3 (YBCO/LSMO) bilayers were grown by magnetron sputtering on sapphire (Al2O3 or ALO) substrates. Temperature dependences of resistance of single LSMO films, grown on ALO substrates were typical for polycrystalline manganite materials and the resistance decreased with decrease of the temperature at medium temperatures and increased at lower and higher temperatures. Deposition of a top YBCO layer led to a drastic increase of the sample resistance. These bilayers did not demonstrate a decreasing of the resistance with decrease of tempe…
Silver nanoparticles embedded in a dielectric matrix are investigated for their potential as broadband-absorbing optical sensor materials. This contribution focuses on the electrical properties of silver nanoparticles at various morphological stages. The electrical current through thin films, consisting of silver nanoparticles, was characterized as a function of film thickness. Three distinct conductivity zones were observed. Two relatively flat zones ("dielectric" for very thin films and "metallic" for films thicker than 300 - 400 Å) are separated by a sharp transition zone where percolation …
An YBCO-based test structure corresponding to the family of ReRAM devices associated with the valence change mechanism is presented. We have characterized its electrical response previous to its lift-off to a Low Earth Orbit (LEO) using standard electronics and also with the dedicated LabOSat-01 controller. Similar results were obtained in both cases. After about 200 days at LEO on board a small satellite, electrical tests started on the memory device using the LabOSat-01 controller. We discuss the results of the first 150 tests, performed along a 433-day time interval in space. The memory dev…
Anti-ThCr$_2$Si$_2$ type $RE_2$O$_2$Sb ($RE$ = rare earth) with Sb square net has shown insulating conduction so far. Here we report the synthesis of La$_2$O$_2$Sb epitaxial thin films for the first time by multilayer solid-phase epitaxy. The valence state of Sb was about -2 evaluated from X-ray photoemission spectroscopy measurement, and the indirect band gap of 0.17 eV was observed. The La$_2$O$_2$Sb epitaxial thin film showed unexpectedly high electrical conduction as a narrow gap semiconductor, whose resistivity at room temperature was approximately ten-thousand-fold lower than that of La$…
Investigation of electrical conduction in polysilicon nanowires (polySiNW) with nanograins (5 to 20nm), based on Monte Carlo (MC) simulations and electrical measurements from 4K to 300K are presented. Some irregular Coulomb Oscillations (CO) are observed at temperatures lower than 200K showing several period widths due to the random distribution in grain size (5-20nm). A remarkable result consists in more effective oscillations observed at intermediate range of temperatures (between 25K and 150K) and high drain voltages. The temperature dependence of COs is explained by the fact that in a mult…
The implementation of the 2nd generation high-Tc superconductors in power applications, such as electrical transformers, motors and generators requires superconducting wires that are superior to copper Litz wires at cryogenic temperatures in terms of losses in time-varying magnetic field, as well as in engineering current density. Another problem is to find a way to make practical coils and armatures out of flat tape-like conductors with low bending strain tolerance. We discuss several novel approaches to the construction of coils and armatures based specifically on the properties of coated co…
We studied the magnetization losses of four different types of filamentary YBCO coated conductors. A 10 mm wide YBCO coated conductor was subdivided into 20 filaments by laser cutting. The separation of coupling loss from the total is possible because the energy loss per cycle in samples with electrically insulated filaments has a very small frequency dependence. We measured the frequency dependence of the total losses in the frequency range between 0.1 Hz and 500 Hz. The coupling loss was obtained from the total by subtracting the hysteresis loss. The latter was measured at low frequencies si…
Current-voltage measurements have been made at room temperature on a Si-rich silicon oxide film deposited via Electron-Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition (ECR-PECVD) and annealed at 750 - 1000$ ^\circ$C. The thickness of oxide between Si quantum dots embedded in the film increases with the increase of annealing temperature. This leads to the decrease of current density as the annealing temperature is increased. Assuming the Fowler-Nordheim tunneling mechanism in large electric fields, we obtain an effective barrier height $ϕ_{eff}$ of $\sim$ 0.7 $\pm$ 0.1 eV for an e…
We determined the interface state density ($D_{\rm it}$) distributions in the vicinity of the conduction band edge in silicon carbide (SiC) metal-oxide-semiconductor (MOS) structures by reproducing the experimental current-voltage characteristics of MOS field effect transistors (MOSFETs) with numerical calculations. In the calculation, potential distributions and energy sub-bands in the inversion layer were calculated by solving Poisson and Schrödinger equations, respectively. We demonstrate that gate characteristics of the MOSFETs are well described by considering that the interface states ar…
The temperature and electrical field dependent conductivity of n-type CdSe nanocrystal thin films is investigated. In the low electrical field regime, the conductivity follows G ~ exp(-(T*/T)^0.5) in the temperature range 10K<T<120K. At high electrical field, the conductivity is strongly field dependent. At 4K, the conductance increases by eight orders of magnitude over one decade of bias. At very high field, conductivity is temperature-independent with G ~ exp(-(E*/E)^0.5). The complete behavior is very well described by variable range hopping with Coulomb gap.
Tin monosulfide (SnS) usually exhibits p-type conduction due to the low formation enthalpy of acceptor-type defects, and as a result n-type SnS thin films have never been obtained. This study realizes n-type conduction in SnS thin films for the first time by using RF-magnetron sputtering with Cl doping and sulfur plasma source during deposition. N-type SnS thin films are obtained at all the substrate temperatures employed in this study (221-341 C), exhibiting carrier concentrations and Hall mobilities of ~2 x 10 18 cm-3 and 0.1-1 cm V-1s-1, respectively. The films prepared without sulfur plasm…
Among the recent discoveries of domain wall functionalities, the observation of electrical conduction at ferroelectric domain walls in the multiferroic insulator BiFeO3 has opened exciting new possibilities. Here, we report evidence of electrical conduction also at 180° ferroelectric domain walls in the simpler tetragonal ferroelectric PZT thin films. The observed conduction shows nonlinear, asymmetric current-voltage characteristics, thermal activation at high temperatures and high stability. We relate this behavior to the microscopic structure of the domain walls, allowing local defects segr…
We have studied the dark conductivity of a broad microstructural range of plasma deposited single phase undoped microcrystalline silicon films in a wide temperature range (15 - 450K) to identify the possible transport mechanisms and the interrelationship between film microstructure and electrical transport behavior. Different conduction behaviors seen in films with different microstructures are explained in the context of underlying transport mechanisms and microstructural features, for above and below room temperature measurements. Our microstructural studies have shown that different ranges …
Electrical conduction through a two-terminal molecular device is studied using non-equilibrium Green's functions (NEGF) formalism. Such junction is made of a short linear wire which is connected to the metallic electrodes. Molecule itself is described with the help of Huckel (tight-binding) model with the electron interactions treated within extended Hubbard model (EHM), while the coupling to the electrodes is described with the help of a broad-band theory. Coulomb interactions within molecular wire are treated by means of the restricted Hartree-Fock (RHF) approximation. In particular, the inf…
Measurements of the dc transport properties and the low-frequency conductivity noise in films of charge ordered Nd_0.5Ca_0.5MnO_3 grown on Si subtrate reveal the existence of a threshold field in the charge ordered regime beyond which strong non linear conduction sets in along with a large broad band conductivity noise. Threshold-dependent conduction disappears as T -> T_{CO}, the charge ordering temperature. This observation suggests that the charge ordered state gets depinned at the onset of the non-linear conduction.
In order to determine the key parameters that control the resistive switching mechanism in metal-complex oxides interfaces, we have studied the electrical properties of metal / YBa2Cu3O7-d (YBCO) interfaces using metals with different oxidation energy and work function (Au, Pt, Ag) deposited by sputtering on the surface of a YBCO ceramic sample. By analyzing the IV characteristics of the contact interfaces and the temperature dependence of their resistance, we inferred that ion migration may generate or cancel conducting filaments, which modify the resistance near the interface, in accordance …
Controlled breakdown has recently emerged as a highly appealing technique to fabricate solid-state nanopores for a wide range of biosensing applications. This technique relies on applying an electric field of approximately 0.6-1 V/nm across the membrane to induce a current, and eventually, breakdown of the dielectric. However, a detailed description of how electrical conduction through the dielectric occurs during controlled breakdown has not yet been reported. Here, we study electrical conduction and nanopore formation in SiN$_x$ membranes during controlled breakdown. We show that depending o…
We present electrical transport measurements of heterostructures comprised of BaTiO$_3$ and Ba$_{1-x}$Sr$_x$TiO$_3$ epitaxially grown on Ge. The Sr-alloying imparts compressive strain to the BaTiO$_3$, which enables the thermal expansion mismatch between BaTiO$_3$ and Ge to be overcome to achieve $c$-axis oriented growth. The conduction bands of BaTiO$_3$ and Ba$_{1-x}$Sr$_x$TiO$_3$ are nearly aligned with the conduction band of Ge, which facilitates electron transport. Electrical transport measurements through the dielectric stack exhibit rectifying behavior and hysteresis, where the latter i…
Olivine-type LiFePO$_{4}$ is widely considered as a candidate for Li-ion battery electrodes, yet its applicability in the pristine state is limited due to poor ionic and electronic conduction. Doping can be employed to enhance the material's electrical conductivity. However, this should be understood as incorporating electrically active impurities to manipulate the concentration of native point defects such as lithium vacancies and small hole polarons which are responsible for ionic and electronic conduction, respectively, and {\it not} as generating band-like carriers. Possible effects of mon…
We present results of electrical conduction studies of Ti/TiOx/Ti planar structures prepared by tip-induced local anodic oxidation (LAO) of titanium thin films. The prepared structures have shown almost linear I-V curves at temperatures between 300 K and 30 K, and only slight deviation from linear behaviour at lower temperatures. Electrical conductance of the structures can be adequately explained by a two-channel model where variable range hopping channels and metallic ones coexist in parallel, while a crossover from Mott to Efros-Shklovskii variable-range-hopping conductivity has been observ…
We present an atomistic theory of electronic transport through single organic molecules that reproduces the important features of the current-voltage characteristics observed in recent experiments. We trace these features to their origin in the electronic structure of the molecules and their local atomic environment. We demonstrate how conduction channels arise from the molecular orbitals and elucidate which specific properties of the individual orbitals determine their contribution to the current.
We find that the long-range magnetic ordering is absent and electrical conduction suppressed in Y$_{1.7}$Bi$_{0.3}$Ir$_2$O$_7$/YSZ(100) thin film prepared by pulsed laser deposition. The sharp down-turn of inverse magnetic susceptibility X-1(T) from the conventional Curie-Weiss behaviour below T* ~ 168K suggests an inhomogeneous ferromagnetic Griffiths like phase. The transport and magnetic properties are explained on the basis of the coexistence of mixed oxidation states of Ir, (i.e. Ir4+ and Ir3+) leading to non-magnetic defects and reduction in t2g density of states at the Fermi level.
Here we study incoherent transport through molecular wire treated as a linear chain of absorbers, where the phase-breaking processes are modeled by the use of imaginary point-like potentials. The calculations are performed within a transfer-matrix method of the scattering theory. An analytic expression for the transmission of a finite chain in obtained, while the electrical current is then computed with the help of the Tsu-Esaki formula. In particular, it is shown that the maximal current dependence on the wire length is exponential.
Two-dimensional (2D) surface of the topological materials is an attractive channel for the electrical conduction reflecting the linearly-dispersive electronic bands. By applying a reliable systematic thickness t dependent measurement of sheet conductance, here we elucidate the dimensionality of the electrical conduction paths of a Weyl semimetal Co3Sn2S2. Under the ferromagnetic phase, the 2D conduction path clearly emerges in Co3Sn2S2 thin films, indicating a formation of the Fermi arcs projected from Weyl nodes. Comparison between 3D conductivity and 2D conductance provides the effective thi…
We have investigated the electrical conduction processes in as-grown and thermally cycled ZnO single crystal as well as as-grown ZnO polycrystalline films over the wide temperature range 20--500 K. In the case of ZnO single crystal between 110 and 500 K, two types of thermal activation conduction processes are observed. This is explained in terms of the existence of both shallow donors and intermediately deep donors which are consecutively excited to the conduction band as the temperature increases. By measuring the resistivity $ρ(T)$ of a given single crystal after repeated thermal cycling in…
The structures, optical and electrical transport properties of SnO$_2$ films, fabricated by rf sputtering method at different oxygen partial pressures, were systematically investigated. It has been found that preferred growth orientation of SnO$_2$ film is strongly related to the oxygen partial pressure during deposition, which provides an effective way to tune the surface texture of SnO$_2$ film. All films reveal relatively high transparency in the visible range, and both the transmittance and optical band gap increase with increasing oxygen partial pressure. The temperature dependence of res…
Effects of x-ray irradiation on the crystal structure and the electrical resistance were examined at low temperatures for the insulating phase of spinel compound CuIr2S4. We found that the resistance decreases by more than five decades by irradiation at 8.5 K. The structural change from triclinic to tetragonal was observed at the same time. The x-ray-induced conductance is deduced to result from the destruction of Ir4+ dimers formed in the insulating phase. Slow relaxation of the resistance in the x-ray-induced state is also reported.
The temperature dependence of the electrical transport of a individual tin oxide nanobelt was measured, in darkness, from 400 to 5K. We found four intrinsic electrical transport mechanisms through the nanobelt. It starts with Thermal-Activation Conduction between 400 and 314K, Nearest-Neighbor Hopping conduction between 268 and 115K, and Variable Range Hopping conduction below 58K, with a crossover from the 3D-Mott to the 3D-Efros-Shklovskii regime at 16K. We claim that this sequence reveal the three-dimensional nature of the electrical transport in the SnO2 nanobelts, even they are expected t…
The temperature dependent resistance $R$($T$) of polycrystalline ferromagnetic CoFeB thin films of varying thickness are analyzed considering various electrical scattering processes. We observe a resistance minimum in $R$($T$) curves below $\simeq$ 29 K, which can be explained as an effect of intergranular Coulomb interaction in a granular system. The structural and Coulomb interaction related scattering processes contribute more as the film thickness decreases implying the role of disorder and granularity. Although the magnetic contribution to the resistance is the weakest compared to these t…
Germanium single crystal having 45 mm diameter and 100 mm length of 7N+ purity has been grown by Czochralski method. Structural quality of the crystal has been characterized by Laue diffraction. Electrical conduction and Hall measurements are carried out on samples retrieved from different parts of the crystal along the growth axis. Top part of the crystal exhibits lowest impurity concentration (~10^12/cm3) that gradually increases towards the bottom (10^13/cm3). The crystal is n-type at room temperature and the resistivity shows non-monotonic temperature dependence. There is a transition from…
Materials of the Y-Ba-Cu-O (melt-textured YBa2Cu3O7-d-based materials or MT-YBCO) and Mg-B-O (MgB2-based materials) systems with high superconducting performance, which can be attained due to the formation of regularly distributed nanostructural defects and inhomogenities in their structure can be effectively used in cryogenic technique, in particular in fault current limiters and electrical machines (electromotors, generators, pumps for liquid gases, etc.). The developed processes of high-temperature (900-800 oC) oxygenation under elevated pressure (16 MPa) of MT-YBCO and high-pressure (2 GPa…
Electrically steered conduction topologies and period-doubling phase dynamics in VO2
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Laboratory for Ultrafast Transient Facility, Chongqing University（重庆大学超快瞬变设施实验室）；Hebei Key Laboratory of Photophysics Research and Application, Hebei Normal University（河北师范大学光物理研究与应用河北省重点实验室）；Songshan Lake Materials Laboratory（松山湖材料实验室）
We present evidence that electrical transport studies of epitaxial p-type GeMn thin films fabricated on high resistivity Ge substrates are severely influenced by parallel conduction through the substrate, related to the large intrinsic conductivity of Ge due to its small bandgap. Anomalous Hall measurements and large magneto resistance effects are completely understood by taking a dominating substrate contribution as well as the measurement geometry into account. It is shown that substrate conduction persists also for well conducting, degenerate, p-type thin films, giving rise to an effective …
We report first-principles simulation of polarization mechanisms in hydroxyapatite to explain the underlying mechanism behind the reported ion conductivities and polarization under electrical poling at elevated temperatures. It is found that ion conduction occurs mainly in the column of OH$^-$ ions along the $c$-axis through a combination of the flipping of OH$^-$ ions, exchange of proton vacancies between OH$^-$ ions, and the hopping of the OH$^-$ vacancy. The calculated activation energies are consistent with those found in conductivity measurements and thermally stimulated depolarization cu…
We investigate electrical conduction and breakdown behavior of 3D nano-carbon-stacked multilayer graphene (s-MLG) system with complete interlayer decoupling. The s-MLG is prepared by transferring and stacking large-area CVD-grown graphene monolayers, followed by wire patterning and plasma etching. Raman spectroscopy was used to confirm the layer number. The D-band peak indicates low defect level in the samples. Electrical current stressing induced doping is performed to shift the charge-neutrality Dirac point and decrease the graphene/metal contact resistance, improving the overall electrical …
Dielectric behavior and conductivity mechanism in lead-free (100-x)(Li0.12Na0.88)NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics were investigated using impedance spectroscopy over a wide temperature (-100 oC to500 oC) and frequency range (0.1 Hz to1 MHz). The grain and grain boundary response as well as the relaxation processes at different frequencies and temperatures were also discussed. A low frequency dispersion in dielectric permittivity (LFDD), a typical characteristic of high-temperature behavior was observed both below and above the ferro-paraelectric phase transition temperature, …
High Frequency (GW) Post Processing of Transparent Conductive Oxide, ITO, leads to a significant improvement of Optical Transmission and Electrical Conduction. This is also true in case of ITO films in multilayered structures. The improvements happen without any affecting the lower layers (other layers of the multilayered Device). This Method is extremely selective and can process only the targeted film (layer).
In this work, the electrical properties of bilayer Antimonene with different stacking orders are studied. Density functional theory with van der Waals (vdW) correction is used to investigate the electrical performances. Two configurations demonstrate considerable bandgaps, whereas, the bandgaps are close to zero for other structures. The in-plane biaxial strain is applied to modify the electrical properties. The bandgap reaches a maximum at a specific strain level and then closes at more enormous compressive and tensile strains. The energy of three valleys ($Γ$, Q, and K) in the conduction ban…
In this work, the electrical and spin properties of monolayer MoSi2X4 (X= N, P, As, and Sb) under vertical strain are investigated. The band structures state that MoSi2N4 is an indirect semiconductor, whereas other compounds are direct semiconductors. The vertical strain has been selected to modify the electrical properties. The bandgap shows a maximum and decreases for both tensile and compressive strains. The valence band at K-point displays a large spin-splitting, whereas the conduction band has a negligible splitting. On the other hand, the second conduction band has a large spin-splitting…
Thin films composed of Ge nanocrystals embedded in amorphous SiO2 matrix (Ge-NCs TFs) were prepared using a low temperature in-situ growth method. Unexpected high p-type conductivity was observed in the intrinsic Ge-NCs TFs. Unintentional doping from shallow dopants was excluded as a candidate mechanism of hole generation. Instead, the p-type characteristic was attributed to surface state induced hole accumulation in NCs, and the hole conduction was found to be a thermally activated process involving charge hopping from one NC to its nearest neighbor. Theoretical analysis has shown that the de…
Silver nanowires have great application potential in fields like flexible electronic devices, solar cells and transparent electrodes. It is critical and fundamental to study the thermal and electrical transport properties in a single silver nanowire. In this work, the thermal and electrical transport in an individual silver nanowire is characterized down to 35 K with the steady state electro-thermal technique. The results indicate that, at room temperature, the electrical resistivity increases by around 4 folds compared from that of its bulk counterpart. After fitting the temperature dependent…
A multilayer perovskite thin film resistive memory device has been developed comprised of: a Pr0.7Ca0.3MnO3 (PCMO) perovskite oxide epitaxial layer on a YBCO bottom thin film electrode; a thin yttria stabilized zirconia (YSZ) buffer layer grown on the PCMO layer, and a gold thin film top electrode. The multi-layer thin film lattice structure has been characterized by XRD and TEM analyses showing a high quality heterostructure. I-AFM analysis indicated nano granular conductivity distributed uniformly throughout the PCMO film surface. With the addition of the YSZ buffer layer, the pulse voltage …
The intrinsic d.c. electrical resistivity ($ρ$) - measurable on single crystals only - is often the quantity first revealing the properties of a given material. In the case of CH$_3$NH$_3$PbI$_3$ perovskite measuring $ρ$ under white light illumination provides insight into the coexistence of extended and shallow localized states (0.1 eV below the conduction band). The former ones dominate the electrical conduction while the latter, coming from neutral defects, serve as a long-lifetime charge carrier reservoir accessible for charge transport by thermal excitation. Remarkably, in the best crysta…
Diffusive memristors continue to receive tremendous interest due to their ability to emulate biological neurons and thus aid the development of bio-inspired computation technology. A major issue with the diffusive memristor is the inability to reliably control the formation of the conduction filaments which affects both the device functionality and reproducibility of regimes after each application of voltage. Here we investigate the effect of gamma radiation on the electrical properties of the diffusive memristors based on metallic nanoparticles in dielectric matrix. Our experiments show that …
We have fabricated oxygen deficient polycrystalline ZnO films by the rf sputtering deposition method. To systematically investigate the charge transport mechanisms in these samples, the electrical resistivities have been measured over a wide range of temperature from 300 K down to liquid-helium temperatures. We found that below about 100 K, the variable-range-hopping (VRH) conduction processes govern the charge transport properties. In particular, the Mott VRH conduction process dominates at higher temperatures, while crossing over to the Efros-Shklovskii (ES) VRH conduction process at lower t…
Probing Electromigration of Oxygen Vacancies in YBa$_2$Cu$_3$O$_{7-δ}$ Devices by Multimodal X-ray Techniques
Universidade Federal de São Carlos（圣卡洛斯联邦大学）；National High Magnetic Field Laboratory, Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室国家高磁场实验室）；Université de Liège（列日大学）；Centro Brasileiro de Pesquisas Físicas（巴西物理研究中心）；Institut de Ciència de Materials de Barcelona, ICMAB-CSIC（巴塞罗那材料科学研究所）；Brazilian Nanotechnology National Laboratory, Brazilian Center for Research in Energy and Materials（巴西纳米技术国家实验室、巴西能源与材料研究中心）
High-quality, large-area epitaxial graphene can be grown on metal surfaces but its transport properties cannot be exploited because the electrical conduction is dominated by the substrate. Here we insulate epitaxial graphene on Ru(0001) by a step-wise intercalation of silicon and oxygen, and the eventual formation of a SiO$_2$ layer between the graphene and the metal. We follow the reaction steps by x-ray photoemission spectroscopy and demonstrate the electrical insulation using a nano-scale multipoint probe technique.
Quantum spin liquid states, in which spins are quantum-mechanically delocalized in direction, have been so far studied for charge-localized Mott insulators arising from strong repulsive interaction. Recently, however, it was found that the doped Mott insulator with a triangular lattice, $κ$-(ET)$_4$Hg$_{2.89}$Br$_8$, exhibits both spin-liquid-like magnetism and metallic electrical conduction. Thus, it is now possible to experimentally explore how the spin liquidity affects the electrical conduction, an issue that has received a great deal of theoretical attention. Here, with a newly developed …
