Structural and mass transport properties of liquid ytterbium in the temperature range 1123 K–1473 K

We have studied the structural and atomic transport properties of liquid f-shell Yb in the temperature range 1123 K–1473 K. Pair interactions between atoms are derived using a local pseudopotential. The potential parameters are fitted to the phonon dispersion curve at room temperature. The local pseudopotential used in the present study is computationally more efficient with only three parameters, and it is found to be transferable to the liquid phase without changing the parameters.Since the various computed properties agree with reported theoretical and experimental findings, the adopted fitting scheme is justified. As a significant outcome of the study, we find that(i) the melting in Yb is governed by the Lindemann's law,(ii)the mass transport mechanism obeys the Arrhenius law,(iii) the role of the three-particle correlation function in deriving the velocity autocorrelation function is small,(iv) the mean-square atomic displacement is more sensitive to the choice of interaction potential than the other bulk properties, and(v) liquid Yb does not show liquid–liquid phase transition within the studied temperature range. Further, due to the good description of the structural and mass transport properties, we propose that Yb remains divalent at reduced density.

Determination of the transport properties in 4H-SiC wafers by Raman scattering measurement

The free carrier density and mobility in n-type 4H-SiC substrates and epilayers were determined by accurately analysing the frequency shift and the full-shape of the longitudinal optic phono-plasmon coupled （LOPC） modes, and compared with those determined by Hall-effect measurement and that provided by the vendors. The transport properties of thick and thin 4H-SiC epilayers grown in both vertical and horizontal reactors were also studied. The free carrier density ranges between 2× 10^18 cm^-3 and 8× 10^18 cm^-3with a carrier mobility of 30-55 cm2/（V.s） for ntype 4H-SiC substrates and 1× 10^16 -3× 10^16 cm^-3 with mobility of 290-490 cm2/（V.s） for both thick and thin 4H-SiC epilayers grown in a horizontal reactor, while thick 4H-SiC epilayers grown in vertical reactor have a slightly higher carrier concentration of around 8.1×10^16 cm^-3 with mobility of 380 cm2/（V.s）. It was shown that Raman spectroscopy is a potential technique for determining the transport properties of 4H-SiC wafers with the advantage of being able to probe very small volumes and also being non-destructive. This is especially useful for future mass production of 4H-SiC epi-wafers.

Transport properties of Tl_(2)Ba_(2)CaCu_(2)O_(8) microbridges on a low-angle step substrate

Tl-based superconducting devices have been drawn much attention for their high transition temperature(T_c), which allow the high temperature superconductors(HTS) devices to operate at temperature near 100 K. The realization of Tlbased devices will promote the research and application of HTS devices. In this work, we present transport properties of Tl_(2) Ba_(2) CaCu_(2) O_(8)(Tl-2212) microbridges across a low-angle step on LaAlO_(3)(LAO) substrate. We experimentally demonstrate intrinsic Josephson effects(IJEs) in Tl-2212 films by tailoring the geometry, i.e., reducing the width of the microbridges. In the case of a 1 μm width microbridge, in addition to the observation of voltage branches and remarkable hysteresis on the current–voltage(I–V) characteristics, the temperature dependence of differential resistance shows a finite resistance above 60 K when the bias current is below the critical current. For comparison, the wider microbridges are also investigated, exhibiting a highly critical current but do not showing obvious IJEs.

Transport Properties of LCMO Granular Films Deposited by the Pulsed Electron Deposition Technique

By finely controlling the deposition parameters in the pulsed electron deposition process, granular La 2/3 Ca 1/3 MnO 3 （LCMO） film was grown on silicon substrates. The substrate temperature, ambient pressure in the deposition chamber and acceleration potential for the electron beam were all found to affect the grain size of the film, resulting in different morphologies of the samples. Transport properties of the obtained granular films, especially the magnetoresistance （MR）, were studied. Prominent low-field MR was observed in all samples, indicating the forming of grain boundaries in the sample. The low-field MR show great sensitive to the morphology evolution, which reaches the highest value of about 40% for the sample with the grain size of about 250 nm. More interestingly, positive-MR （p-MR） was also detected above 300 K when low magnetic field applying, whereas it disappeared with higher magnetic field applied up to 1.5 and 2 Tesla. Instead of the spin- polarized tunneling process being commonly regarded as a responsible reason, lattice mismatch between LCMO film and silicon substrate appears to be the origin of the p-MR

Transport properties of zigzag graphene nanoribbons adsorbed with single iron atom

We have performed density-functional calculations of the transport properties of the zigzag graphene nanoribbon （ZGNR） adsorbed with a single iron atom. Two adsorption configurations are considered, i.e., iron adsorbed on the edge and on the interior of the nanoribbon. The results show that the transport features of the two configurations are similar. However, the transport properties are modified due to the scattering effects induced by coupling of the ZGNR band states to the localized 3d-orbital state of the iron atom. More importantly, one can find that several dips appear in the transmission curve, which is closely related to the above mentioned coupling. We expect that our results will have potential applications in graphene-based spintronic devices,

Transport properties of boron nanotubes investigated by ab initio calculation

We investigate atomic and electronic structures of boron nanotubes （BNTs） by using the density functional theory （DFT）. The transport properties of BNTs with different diameters and chiralities are studied by the Keldysh nonequilibrium Green function （NEGF） method. It is found that the cohesive energies and conductances of BNTs decrease as their diameters decrease. It is more difficult to form （N, 0） tubes than （M, M） tubes when the diameters of the two kinds of tubes are comparable. However, the （N, 0） tubes have a higher conductance than the （M, M） tubes. When the BNTs are connected to gold electrodes, the coupling between the BNTs and the electrodes will affect the transport properties of tubes significantly.

Strain effect on transport properties of hexagonal boron—nitride nanoribbons

The transport properties of hexagonal boron-nitride nanoribbons under the uniaxial strain are investigated by the Green＇s function method. We find that the transport properties of armchair boron-nitride nanoribbon strongly depend on the strain. In particular, the features of the conductance steps such as position and width are significantly changed by strain. As a strong tensile strain is exerted on the nanoribbon, the highest conductance step disappears and subsequently a dip emerges instead. The energy band structure and the local current density of armchair boron nitride nanoribbon under strain are calculated and analysed in detail to explain these characteristics. In addition, the effect of strain on the conductance of zigzag boron-nitride nanoribbon is weaker than that of armchair boron nitride nanoribbon.

Transport properties of warm and hot dense iron from orbital free and corrected Yukawa potential molecular dynamics

The equation of states,diffusions,and viscosities of strongly coupled Fe at 80 and 240 eV with densities from 1.6 to 40 g/cm^(3) are studied by orbital-free molecular dynamics,classical molecular dynamics with a corrected Yukawa potential and compared with the results from average atom model.A new local pseudopotential is generated for orbital free calculations.For low densities,the Yukawa model captures the correct ionic interaction behavior around the first peak of the radial distribution function(RDF),thus it gives correct RDFs and transport coefficients.For higher densities,the scaled transformation of the Yukawa potential or adding a short range repulsion part to the Yukawa potential can give correct RDFs and transport coefficients.The corrected potentials are further validated by the force matching method.

Transport properties and microstructure of La_(0.7)Sr_(0.3)MnO_3 nanocrystalline thin films grown by polymer-assisted chemical solution deposition

Perovskite-based materials can be widely used in the aerospace and transportation field. Perovskite man-ganese oxides La0.7Sr0.3MnO3 （LSMO） thin films were grown on LaAlO3 （100） and Si （100） single crystal sub-strates by the polymer-assisted chemical solution deposi-tion （PACSD） method. Electronic transport behavior, microstructure, and magnetoresistance （MR） of LSMO thin films on different substrates were investigated. The resis-tance of LSMO films fabricated on LaAlO3 substrates is smaller than that on the Si substrates. The magnetic field reduces resistance of LSMO films both on Si and LAO in the wide temperature region, when the insulator-metal transition temperature shifts to higher temperature. The low-field magnetoresistance of LSMO films on Si in low temperature range at 1 T is larger than that of LSMO films on LAO. However, the MR of LSMO film on LAO films at room-temperature is about 5.17%. The thin films are smooth and dense with uniform nanocrystal size grain. These results demonstrate that PACSD is an effective technique for producing high quality LSMO films, which is significant to improve the magnetic properties and the application of automotive sensor.

Effect of Chemical Doping on the Electronic Transport Properties of Tailoring Graphene Nanoribbons

The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons（AGNRs）with different widths are investigated by applying the non-equilibrium Green＇s function formalism combined with first-principles density functional theory.The calculated results show that the width and doping play significant roles in the electronic transport properties of the molecular junction.A higher current can be obtained for the molecular junctions with the tailoring AGNRs with W=11.Furthermore,the current of boron-doped tailoring AGNRs with widths W=7 is nearly four times larger than that of the undoped one,which can be potentially useful for the design of high performance electronic devices.

Effect of Chirality on the Electronic Transport Properties of the Thioxanthene-Based Molecular Switch

Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch. The molecule comprises the switch which can exhibit different chiralities, that is, cis-form and trans-form by ultraviolet or visible irradiation. The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form. ~urthermore, the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes. The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction, suggesting potential applications of this type of junctions in future design of functional molecular devices.

Transport properties of doped Bi2Se3 and Bi2Te3 topological insulators and heterostructures

In this review article, the recent experimental and theoretical research progress in Bi2Se3-and Bi2Te3-based topological insulators is presented, with a focus on the transport properties and modulation of the transport properties by doping with nonmagnetic and magnetic elements. The electrical transport properties are discussed for a few different types of topological insulator heterostructures, such as heterostructures formed by Bi2Se3-and Bi2Te3-based binary/ternary/quaternary compounds and superconductors, nonmagnetic and magnetic metals, or semiconductors.

Effect of Zn Doping on Transport Properties of La_(2/3)Sr_(1/3)Mn_(1-x)Zn_xO_3 Films

La2/3 Sr1/3 Mn1-x ZnxO3films （x =0.05, 0.1,0.3, and 0.5） were prepared using magnetron sputtering method, and the effect of Zn doping on transport properties of the films was studied. An analysis of X-ray diffraction showed that the main phase of the bulk target was orthorhombic and the films had better epitaxial character. It was found that the films with x =0.05 and x =0.1 exhibited typical insulator-metal transition. No transition of the films with x≥0.3 was observed and the dominant transport was variable-range hopping due to observable secondary phase ZnO. These could be attributed to the Zn doping effect on manganites.

Electrical Transport Properties of Type-Ⅷ Sn-Based Single-Crystalline Clathrates (Eu/Ba)8Ga16Sn30 Prepared by Ga Flux Method

Single-crystalline samples of Eu/Ba-filled Sn-based type-Ⅷ clathrate are prepared by the Ga flux method with different stoichiometric ratios. The electrical transport properties of the samples are optimized by Eu doping. Results indicate that Eu atoms tend to replace Ba atoms. With the increase of the Eu initial content, the carrier density increases and the carrier mobility decreases, which leads to an increase of the Seebeck coefficient. By contrast, the electrical conductivity decreases. Finally, the sample with Eu initial content of x = 0.75 behaves with excellent electrical properties, which shows a maximal power factor of 1.51 mW·m^-1K^-2 at 480K, and the highest ZT achieved is 0.87 near the temperature of 483K.

Transport properties and anomalous fatigue effect of Ag/Bi_(0.9)La_(0.1)FeO_3/La_(0.7)Sr_(0.3)MnO_3 heterostructures

The transport properties and fatigue effect of Ag/Bi0.9La0.lFeO3/La0.7Sr0.3MnO3 heterostructures are described. By examining the I-V curves, an anomalous fatigue effect was found and its influences on resistive states were studied. I-V curves combined with C-f spectra were used to directly analyze the transport properties and fatigue effect. Compared to the first I-V cycle state, this structure shows more than one order increase of resistance after 100 cycles of ＂I-V curve training＂. The redistribution of oxygen vacancies in the depletion layer of Ag/Bi0.9La0.lFeO3 is believed to be responsible for the different resistance mechanisms and tenfold magnitude drop in resistance. The resistive switching is understood to be caused by electric field-induced carrier trapping and detrapping, which changes the depletion layer thickness at the Ag/Bi0.9La0.lFeO3 interface.

Magnetic Transport Properties of Fe-Phthalocyanine Dimer with Carbon Nanotube Electrodes

Based on the non-equilibrium Green＇s method and density functional theory, the magnetic transport of Fe- phthMocyanine dimers with two armchair single-wailed carbon nanotube electrodes is investigated. The results show that the system can present high-performance spin filtering, magnetoresistance, and low-bias spin negative differential resistance effects by tuning the external magnetic field. These results show that the Fe-phthalocyanine dimer has the potential to design future molecular spintronic devices.

Transport properties of mixing conduction in CaF_2 nanocrystals under high pressure

We report on the intriguing electrical transport properties of compressed CaF2 nanocrystals. The diffusion coefficient, grain and grain boundary resistances vary abnormally at about 14.37 GPa and 20.91 GPa, corresponding to the beginning and completion of the Fm3m-Pnma structural transition. Electron conduction and ion conduction coexist in the transport process and the electron conduction is dominant. The electron transference number of the Fm3m and Pnma phases increases with pressure increasing. As the pressure rises, the F ion diffusion and electronic transport processes in the Fm3m and Pnma phases become more difficult. Defects at grains play a dominant role in the electronic transport process.

Ferromagnetic-insulators-modulated transport properties on the surface of a topological insulator

Transport properties on the surface of a topological insulator （TI） under the modulation of a two-dimensional （2D） ferromagnet/ferromagnet junction are investigated by the method of wave function matching. The single ferromagnetic barrier modulated transmission probability is expected to be a periodic function of the polarization angle and the planar rotation angle, that decreases with the strength of the magnetic proximity exchange increasing. However, the transmission probability for the double ferromagnetic insulators modulated n-n junction and n-p junction is not a periodic function of polarization angle nor planar rotation angle, owing to the combined effects of the double ferromagnetic insulators and the barrier potential. Since the energy gap between the conduction band and the valence band is narrowed and widened respectively in ranges of 0 ≤ 0 〈π/2 and r/2 〈 0 ≤ π, the transmission probability of the n-n junction first increases rapidly and then decreases slowly with the increase of the magnetic proximity exchange strength. While the transmission probability for the n-p junction demonstrates an opposite trend on the strength of the magnetic proximity exchange because the band gaps contrarily vary. The obtained results may lead to the possible realization of a magnetic/electric switch based on TIs and be useful in further understanding the surface states of TIs.

Epitaxial growth and transport properties of compressively-strained Ba_(2)IrO_(4) films

Ba_(2)IrO_(4) is a sister compound of the widely investigated Sr_(2)IrO_(4) and has no IrO_(6) octahedral rotation nor net canted antiferromagnetic moment,thus it acts as a system more similar to the high-T_(c) cuprate.In this work,we synthesize the Ba_(2)IrO_(4) epitaxial films by reactive molecular beam epitaxy and study their crystalline structure and transport properties under biaxial compressive strain.High resolution scanning transmission electron microscopy and x-ray diffraction confirm the high quality of films with partial strain relaxation.Under compressive epitaxial strain,the Ba_(2)IrO_(4) exhibits the strain-driven enhancement of the conductivity,consistent with the band gap narrowing and the stronger hybridization of Ir-t_(2g) and O-2p orbitals predicted in the first-principles calculations.

Hydration effect on the electronic transport properties of oligomeric phenylene ethynylene molecular junctions

A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 （2007）]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.