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Magnetic skyrmions are promising candidates for next-generation information carriers. Many concepts and prototypes for skyrmion-based devices have been proposed, and most of the studies are based on the motion of isolated skyrmion. Nevertheless, so far, a comprehensive research of multi-skyrmion motion and related device design are still lacking. In this work, a skyrmion subtracter and a skyrmion diverter based on multi-skyrmion motion are numerically demonstrated in a voltage-gated synthetic antiferromagnetic racetrack. It shows that the number of skyrmions along an array n can be subtracted by an integer from 1 to n by proper control of the driving current density and the voltage-controlled magnetic anisotropy in a narrow racetrack, realizing the function of a skyrmion subtracter. Moreover, when the width of racetrack increases, a single array of skyrmions along the racetrack direction can redistribute along the voltage gate due to the blocking effect of the voltage-controlled magnetic anisotropy. As a result, the single array of skyrmions can split into several arrays, realizing the function of a skyrmion diverter. Our results thus provide guidelines for designing novel racetrack-type skyrmionic devices. [ABSTRACT FROM AUTHOR]

Fe3O4 nanoparticles have been conjugated to curcumin (CU) molecules via a citrate (CA) linker (Fe-CA-CU) and have been explored for superoxide scavenging, tumor suppression, and cancer hyperthermia. The conjugation chemistry reveals that Fe3+ ions on the nanoparticle surface readily conjugates to the available carboxyl sites on the CA molecule, which further conjugates to CU at its central enol -OH group. As seen from the UV-vis spectroscopy, the therapeutically active chromophore group of CU, which is seen at 423 nm, was intact, ensuring the activity the molecule. Magnetization measurements showed good hysteresis curves of Fe3O4 and Fe-CA-CU, indicating the presence of magnetism after conjugation. The loading percentage of citrate-curcumin was seen to be ∼10% from the thermo-gravimetric analysis. The systems when subjected to radio-frequency fields of 240 KHz, were seen to get heated up. The Fe3O4 heating exhibited better slope (1 °C/s) as compared to the Fe-CA-CU system (∼0.7 °C/s) for a sample of concentration 10 mg/ml in average time of ∼20 s to reach the required hyperthermia threshold temperature of ∼45 °C. Tumor suppression studies were done using potato assay, which showed that while only CU showed 100% suppression in 7 days, it was about 89% by the Fe-CA-CU. Upon subjecting these systems to the superoxide anion scavenging assay and superoxide radical scavenging assay (riboflavin), it was observed that the activity was enhanced in the Fe-CA-CU to 40% (from 38% in only CU) and 100% (from 5.75% in only CU). These studies promise Fe-CA-CU as a good cancer hyperthermia-cum-tumor suppressant and antioxidant agent. [ABSTRACT FROM AUTHOR]

ZnO film with high crystal quality was prepared on InN/sapphire substrate by metal organic chemical vapor deposition. The diffusion of nitrogen (N) into ZnO film was investigated via Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), and low-temperature photoluminescence (LT-PL). AES revealed that some N atoms out-diffused into ZnO film after a rapid thermal annealing (RTA) process, while most of the In atoms remained in InN layers, which was confirmed by XPS. LT-PL spectra at 10 K further confirmed that N atoms diffused into the upper ZnO film and acted as acceptors after RTA. It might be an attractive way to obtain high-quality p-type ZnO:N on InN films by this thermal diffusion doping technique. [ABSTRACT FROM AUTHOR]

The depolarization effect (DE) in the intersubband transitions (ISBTs) of triangular cross-section quantum wires has been calculated in the framework of the effective-mass envelope-function theory and the self-consistent field approximation (Hartree approximation). Similar to quantum wells, the DE can bring an upward shift in ISBT. The shift quantities are affected significantly by apex angle but are insensitive to triangle size. [ABSTRACT FROM AUTHOR]

The structures and thermoelectric properties of mCu5Zn3·nZn4Sb3 with multiphase coexistence are reported. Rietveld analysis reveals that at least 92.3% wt % β-Zn4Sb3 phase can be obtained with only small quantities of ZnSb and Cu5Zn8 phases precipitated after proper Cu5Zn3 addition. Measurements indicate that although the β-Zn4Sb3 phase plays a determining role in controlling the transport properties involving the Seebeck coefficient, electrical conductivity, and thermal conductivity, the impurity phases Cu5Zn8 and ZnSb with a crooked riverlike and intertwined tree stump morphologies, respectively, are still of great significance to tune the thermoelectric performance. The highest ZT value of 0.84 can be obtained for the alloy mCu5Zn3·nZn4Sb3 (m/n=1/200) at 631 K, approximately 1.8 times that of undoped β-Zn4Sb3, proving that a good combination between the transports of carriers and phonons can be achieved if a proper dopant is introduced in the Zn4Sb3 matrix. [ABSTRACT FROM AUTHOR]

This work aims to give a comprehensive view of magnetic state stability and transformations in PZT-film/FeGa-dot multiferroic composite systems due to the combining effects of size, shape and interfacial coupling strain. It is found that the stable magnetic state of the FeGa nanodots is not only a function of the size and shape of the nanodot but also strongly sensitive to the interfacial coupling strain modified by the polarization state of PZT film. In particular, due to the large magnetostriction of FeGa, the phase boundaries between different magnetic states (i.e., in-plane/out-of-plane polar states, and single-/multi-vortex states) of FeGa nanodots can be effectively tuned by the polarization-mediated strain. Fruitful strain-mediated transformation paths of magnetic states including those between states with different orderings (i.e., one is polar and the other is vortex), as well as those between states with the same ordering (i.e., both are polar or both are vortex) have been revealed in a comprehensive view. Our result sheds light on the potential of utilizing electric field to induce fruitful magnetic state transformation paths in multiferroic film-dot systems towards a development of novel magnetic random access memories. [ABSTRACT FROM AUTHOR]

Resonant Raman spectroscopy requires that the wavelength of the laser used is close to that of an electronic transition. A tunable laser source and a triple spectrometer are usually necessary for resonant Raman profile measurements. However, such a system is complex with low signal throughput, which limits its wide application by scientific community. Here, a tunable micro-Raman spectroscopy system based on the supercontinuum laser, transmission grating, tunable filters, and single-stage spectrometer is introduced to measure the resonant Raman profile. The supercontinuum laser in combination with transmission grating makes a tunable excitation source with a bandwidth of sub-nanometer. Such a system exhibits continuous excitation tunability and high signal throughput. Its good performance and flexible tunability are verified by resonant Raman profile measurement of twisted bilayer graphene, which demonstrates its potential application prospect for resonant Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Phase field simulations are performed to investigate the domain structures of soft ferromagnetic nanodots. It is found that the stability of the domain state is sensitive to its lateral dimensions. As the lateral dimensions increase, the stable domain state gradually changes from polar to vortex, with a transitional region where both the two ordered states are stable. Interestingly, the phase diagram is also a strong function of mechanical loads. By appropriately choosing the lateral dimensions, transformations between polar and vortex states can be induced or controlled by mechanical loads. The study provides instructive information for the applications of ferromagnetic nanostructures. [ABSTRACT FROM AUTHOR]

Excitation of surface plasmons enables super-Planckian thermal radiation far beyond the blackbody limit. By patterning a single layer of graphene sheet into ribbons, the closed circular dispersion of graphene plasmons is opened to become hyperbolic, leading to broadband singularities of density of states. Extremely high-k evanescent waves can now couple with hyperbolic graphene plasmons. Consequently, a giant enhancement of the near-field radiative heat flux, by more than one order of magnitude, is demonstrated in this study using rigorous numerical simulations. The findings may open promising pathways for highly efficient thermal management, energy harvesting, and subwavelength thermal imaging. [ABSTRACT FROM AUTHOR]

Pb(Zr0.53Ti0.47)O3 (PZT) thin film was fabricated on Pt/Ti/SiO2/Si substrate by chemical solution deposition method. Our results show a very great switchable ferroelectric diode effect (SFDE) in Pt-PZT-Au structure, which is more obvious and controllable than that in other ferroelectric thin films. The electrical conduction exhibits high rectifying behavior after pre-poling and the polarity of ferroelectric diode can be switched by changing the orientation of polarization in ferroelectric thin film. Our results also indicate that the SFDE in PZT film is highly dependent on remanent polarization and temperature. With the increase of remanent polarization, the forward current of bistable rectifying behavior observably reduces. Therefore, our measurement indicated that the biggest rectification ratio can reach about 220, which is found in 250K after +10V poling. By analyzing the conduction data, it is found that the dominant conduction mechanism of the SFDE in this sample is due to the space-charge-limited bulk conduction (SCLC), and Schottky emission (SE) may play subordinate role in forward bias voltage. Our observation demonstrates that SFDE may be general characteristic in ferroelectrics as long as proper electrodes chosen. [ABSTRACT FROM AUTHOR]

Graphene has attracted great attention in nanoelectronics, optics, and energy harvesting. Here, the near-field radiative heat transfer between graphene-covered corrugated silica is investigated based on the exact scattering theory. It is found that graphene can improve the radiative heat flux between silica gratings by more than one order of magnitude and alleviate the performance sensitivity to lateral shift. The underlying mechanism is mainly attributed to the improved photon tunneling of modes away from phonon resonances. Besides, coating with graphene leads to nonlocal radiative transfer that breaks Derjaguin's proximity approximation and enables corrugated silica to outperform bulk silica in near-field radiation. [ABSTRACT FROM AUTHOR]

The near-field radiative heat transfer for two hyperbolic metamaterials, namely, graphite and vertically aligned carbon nanotubes (CNTs), is investigated. Graphite is a naturally existing uniaxial medium, while CNT arrays can be modeled as an effective anisotropic medium. Different hyperbolic modes can be separately supported by these materials in certain infrared regions, resulting in a strong enhancement in near-field heat transfer. It is predicted that the heat flux between two CNT arrays can exceed that between SiC plates at any vacuum gap distance and is about 10 times higher with a 10 nm gap. [ABSTRACT FROM AUTHOR]

Based on the set of nonlinear coupling equations, which has considered the relativistic effects of electrons, modulational instability by strong Langmuir waves has been investigated in this paper. Both the characteristic scale and maximum growth rate of the Langmuir field will enhance with the increase in the electron relativistic effect. The numerical results indicate that longitudinal perturbations induce greater instability than transverse perturbations do, which will lead to collapse and formation of the pancake-like structure. [ABSTRACT FROM AUTHOR]

Using a kinetic description, the relativistically strong Langmuir turbulence is investigated, which has considered the nonlinear wave-wave, wave-particle interactions and the relativistic effects of electrons. The relativistic Zakharov equations have been obtained. On the basis of these equations, dynamics of collapse has been studied. It is shown that the field strength of relativistic Langmuir plasmons will increase and the ponderomotive expulsion of particles gives rise to the formation of density caviton during the collapsing, which is useful for understanding the natural structural element of relativistically strong Langmuir turbulence [ABSTRACT FROM AUTHOR]

The instantaneous spectra of the transverse, Langmuir, and ion-sound plasmons near the critical surface in a laser-plasma are numerically obtained from the complete Zakharov equations under the condition of the nonstatic limit. They are used to discuss the filamentation process in the strong Langmuir turbulence. From the turbulence spectra, the energy flux flow from small k space to large k space can be identified. The higher incident laser intensity associated with a quicker filamentation process can also be identified. [ABSTRACT FROM AUTHOR]

A new method and associating system has been presented to characterize pre-pulses of femtosecond laser using laser filamentation in transparent media. Pre-pluses of the laser system has been measured experimentally and it is in good agreement with the results obtained by third order cross-correlator. This method can be used for fast detection of temporal laser intensity relatively in order to avoid formation of pre-plasmas before laser matter interaction experiments. [ABSTRACT FROM AUTHOR]

An x-ray pinhole camera and a monochromatic Kα imager are used to measure the interactions of intense femtosecond laser pulses with Cu foil targets. The two diagnostics give different features in the spot size and the laser energy scaling, which are resulted from different physical processes. Under our experimental conditons, the Kα emission is mainly excited by the fast electrons transporting inside the cold bulk target. In contrast, the x-ray pinhole signals are dominated by the broadband thermal x-ray emission from the hot plasma at the front target surface. [ABSTRACT FROM AUTHOR]

Temperature-dependent photoluminescence characteristics of non-polar m-plane ZnO and ZnMgO alloy films grown by metal organic chemical vapor deposition have been studied. The enhancement in emission intensity caused by localized excitons in m-plane ZnMgO alloy films was directly observed and it can be further improved after annealing in nitrogen. The concentration of Zn vacancies in the films was increased by alloying with Mg, which was detected by positron annihilation spectroscopy. This result is very important to directly explain why undoped Zn1-xMgxO thin films can show p-type conduction by controlling Mg content, as discussed by Li et al. [Appl. Phys. Lett. 91, 232115 (2007)]. [ABSTRACT FROM AUTHOR]

In2O3 is a promising partner of InN to form InN/In2O3 heterosystems. The valence band offset (VBO) of wurtzite InN/cubic In2O3 heterojunction is determined by x-ray photoemission spectroscopy. The valence band of In2O3 is found to be 1.47±0.11 eV below that of InN, and a type-I heterojunction with a conduction band offset (CBO) of 0.49–0.99 eV is found. The accurate determination of the VBO and CBO is important for use of InN/In2O3 based electronic devices. [ABSTRACT FROM AUTHOR]

The valence band offsets of the wurtzite polar C-plane and nonpolar A-plane InN/ZnO heterojunctions are directly determined by x-ray photoelectron spectroscopy to be 1.76±0.2 eV and 2.20±0.2 eV. The heterojunctions form in the type-I straddling configuration with a conduction band offsets of 0.84±0.2 eV and 0.40±0.2 eV. The difference of valence band offsets of them mainly attributes to the spontaneous polarization effect. Our results show important face dependence for InN/ZnO heterojunctions, and the valence band offset of A-plane heterojunction is more close to the “intrinsic” valence band offset. [ABSTRACT FROM AUTHOR]

The valence band offset (VBO) of InN/4H-SiC heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be 0.55±0.23 eV and the conduction band offset is deduced to be -2.01±0.23 eV, indicating that the heterojunction has a type-I band alignment. The accurate determination of the valence and conduction band offsets is important for applications of InN/SiC optoelectronic devices. [ABSTRACT FROM AUTHOR]

The valence band offset (VBO) of MgO(111)/4H-SiC heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be 3.65±0.23 eV and the conduction band offset is deduced to be 0.92±0.23 eV, indicating that the heterojunction has a type-I band alignment. The accurate determination of the valence and conduction band offsets is important for the applications of MgO/SiC optoelectronic devices. [ABSTRACT FROM AUTHOR]

The valence band offset (VBO) of the wurtzite ZnO/4H-SiC heterojunction is directly determined to be 1.61±0.23 eV by x-ray photoelectron spectroscopy. The conduction band offset is deduced to be 1.50±0.23 eV from the known VBO value, which indicates a type-II band alignment for this heterojunction. The experimental VBO value is confirmed and in good agreement with the calculated value based on the transitive property of heterojunctions between ZnO, SiC, and GaN. [ABSTRACT FROM AUTHOR]

MgO may be a promising gate dielectric and surface passivation film for InN based devices and the valence band offset of MgO/InN heterojunction has been measured by x-ray photoelectron spectroscopy. The valence band offset is determined to be 1.59±0.23 eV. Given the experimental band gap of 7.83 for the MgO, a type-I heterojunction with a conduction band offset of 5.54±0.23 eV is found. The accurate determination of the valence and conduction band offsets is important for use of MgO/InN electronic devices. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy has been used to measure the valence band offset at the ZnO/GaAs heterojunction interface. The valence band offset is determined to be 2.39±0.23 eV. As a consequence, a type-II heterojunction with a conduction band offset of -0.44±0.23 eV is found. The directly obtained value is in good agreement with the result of theoretical calculations based on the interface-induced gap states and the chemical electronegativity theory. [ABSTRACT FROM AUTHOR]

Bi3.15Nd0.85Ti3O12 thin films of two different preferred orientations were sol-gel grown on Pt/Ti/SiO2/Si. Using different heating rates during crystallization, either films containing 65% columnar grains with (104)/(014) orientation or fine-grained films with a predominant c-axis orientation were obtained. Anisotropic ferroelectric and piezoelectric properties were determined, with a remanent polarization 2Pr=46.4 μC/cm2 and a piezoelectric coefficient d33=17 pm/V in a predominantly (104)/(014)-oriented film, but only 2Pr=16.7 μC/cm2 and d33=5 pm/V in a predominantly c-axis-oriented film. These values confirm that the polarization vector of this material is close to the crystallographic a axis. [ABSTRACT FROM AUTHOR]

The valence band structures of Al–N-codoped [ZnO:(Al, N)] and N-doped (ZnO:N) ZnO films were studied by normal and soft x-ray photoelectron spectroscopy. The valence-band maximum of ZnO:(Al, N) shifts up to Fermi energy level by about 300 meV compared with that of ZnO:N. Such a shift can be attributed to the existence of a kind of Al–N in ZnO:(Al, N), as supported by core level XPS spectra and comparison of modified Auger parameters. Al–N increased the relative quantity of Zn–N in ZnO:(Al, N), while N–N decreased that of Zn–N in ZnO:N. [ABSTRACT FROM AUTHOR]

We observed a transition from film to vertically well-aligned nanorods for ZnO grown on sapphire (0001) substrates by metalorganic chemical vapor deposition. A growth mechanism was proposed to explain such a transition. Vertically well-aligned homogeneous nanorods with average diameters of ∼30, 45, 60, and 70 nm were grown with the c-axis orientation. Raman scattering showed that the E2 (high) mode shifted to high frequency with the decrease of nanorod diameters, which revealed the dependence of nanorod diameters on the stress state. This dependence suggests a stress-driven diameter-controlled mechanism for ZnO nanorod arrays grown on sapphire (0001) substrates. [ABSTRACT FROM AUTHOR]

The depth distribution of the strain-related tetragonal distortion eT in the GaN epilayer with low-temperature AlN interlayer (LT-AlN IL) on Si(111) substrate is investigated by Rutherford backscattering and channeling. The samples with the LT-AlN IL of 8 and 16 nm thickness are studied, which are also compared with the sample without the LT-AlN IL. For the sample with 16-nm-thick LT-AlN IL, it is found that there exists a step-down of eT of about 0.1% in the strain distribution. Meanwhile, the angular scan around the normal GaN <0001> axis shows a tilt difference about 0.01° between the two parts of GaN separated by the LT-AlN IL, which means that these two GaN layers are partially decoupled by the AlN interlayer. However, for the sample with 8-nm-thick LT-AlN IL, neither step-down of eT nor the decoupling phenomenon is found. The 0.01° decoupled angle in the sample with 16-nm-thick LT-AlN IL confirms the relaxation of the LT-AlN IL. Thus the step-down of eT should result from the compressive strain compensation brought by the relaxed AlN interlayer. It is concluded that the strain compensation effect will occur only when the thickness of the LT-AlN IL is beyond a critical thickness. [ABSTRACT FROM AUTHOR]

Bi3.15Nd0.85Ti3O12 (BNdT) thin films were deposited on Pt/Ti/SiO2/Si substrates using a sol-gel process. The film annealed at 750°C is composed of grains of 50–100 nm in diameter. The fine grains show nearly random orientations. “Micropores” were frequently observed at the junctions of the grains and they are mostly amorphous, while sometimes containing very fine crystalline particles with sizes of only a few nanometers. The BNdT film capacitors with a Pt top electrode showed excellent ferroelectric properties. The remanent polarization and the coercive field were in the range of 41–43 μC/cm2 and 70–84 kV/cm, respectively. The BNdT capacitors did not show any significant fatigue up to 5×109 switching cycles at a frequency of 1 MHz. [ABSTRACT FROM AUTHOR]

The intensity of the N K edge in electron energy-loss spectra from a GaN thin film shows a pronounced difference when the orientation of the film approaches the (0002) and (000-2) Bragg reflections, along the polar direction. This experimental result can be interpreted by the effect associated with interference between the Bloch waves of the incident electron in the GaN crystal. The theoretical calculations indicate that, at the Bragg condition of g = 0002 along the Ga-N bond direction, the thickness-averaged electron current density on the N atom plane is much higher than that at g = 000&2macr;, with a maximum as the specimen thickness is about 0.4ξ[sub 0002] (the two-beam extinction distance). The delocalization effect on the experimental spectra is also discussed. [ABSTRACT FROM AUTHOR]

Low-loss all-angle negative refraction is predicted in the mid-infrared region based on doped-silicon nanowire arrays. Loss-enhanced transmission and absence of resonances account for the broadband high figure of merit (FOM), which could be an order of magnitude greater than those reported previously for multilayered metamaterials. At oblique incidence, FOM is found to improve with increasing loss and the physical insight of this counter-intuitive trend is provided. The proposed structure uses doped silicon that is abundant, cheap, nontoxic, and can be fabricated with available processing technology. Furthermore, good tunability can be achieved by varying the doping concentration and volume filling ratio. [ABSTRACT FROM AUTHOR]

A correction to the article "Determination of MgO/AIN heterojunction band offsets by x-ray photoelectron spectroscopy" that was published in the March 24, 2009 issue is presented.

A correction to the article "Anisotropic ferro- and piezoelectric properties of sol-gel grown Bi3.15Nd0.85Ti3O12 films with two different orientations on Pt/Ti/SiO2/Si" that was published in previous issue is presented.

The concentration of hydrogen–indium vacancy complex V[sub In]H[sub 4] in liquid encapsulated Czochralski undoped and Fe-doped n-type InP has been studied by low-temperature infrared absorption spectroscopy. The V[sub In]H[sub 4] complex is found to be a dominant intrinsic shallow donor defect with concentrations up to ∼10[sup 16] cm[sup -3] in as-grown liquid encapsulated Czochralski InP. The concentration of the V[sub In]H[sub 4] complex is found to increase with the compensation ratio in good agreement with the proposed defect formation model of Walukiewicz [W. Walukiewicz, Phys. Rev. B 37, 4760 (1998); Appl. Phys. Lett. 54, 2094 (1989)], which predicts a Fermi-level-dependent concentration of amphoteric defects. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The structures and thermoelectric properties of mCu5Zn3·nZn4Sb3 with multiphase coexistence are reported. Rietveld analysis reveals that at least 92.3% wt % β-Zn4Sb3 phase can be obtained with only small quantities of ZnSb and Cu5Zn8 phases precipitated after proper Cu5Zn3 addition. Measurements indicate that although the β-Zn4Sb3 phase plays a determining role in controlling the transport properties involving the Seebeck coefficient, electrical conductivity, and thermal conductivity, the impurity phases Cu5Zn8 and ZnSb with a crooked riverlike and intertwined tree stump morphologies, respectively, are still of great significance to tune the thermoelectric performance. The highest ZT value of 0.84 can be obtained for the alloy mCu5Zn3·nZn4Sb3 (m/n=1/200) at 631 K, approximately 1.8 times that of undoped β-Zn4Sb3, proving that a good combination between the transports of carriers and phonons can be achieved if a proper dopant is introduced in the Zn4Sb3 matrix. [ABSTRACT FROM AUTHOR]