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With the increasing demand for energy, it has become imperative to investigate the thermoelectric properties that can be beneficial to directly converting heat into electric energy. Here, we theoretically study the thermoelectric transport of the Mn-doped blue phosphorene (blue-P) along the zigzag direction. We show that the spin-polarized electronic transport in the blue-P can be produced by the Mn-doping induced half-metallic energy band structure, and the Seebeck coefficients can take positive and negative values, indicating that the main carriers may be holes and electrons. Thus, the spin-down, spin, and charge Seebeck coefficients show a high peak and a deep valley, while the spin and charge thermoelectric figures of merit show two wide peaks. Moreover, the spin and charge thermoelectric figures of merit are found to be so large that the Mn-doped blue-P along the zigzag direction can be used as good thermoelectric materials. In addition, we consider the effect of the doping concentration on the electronic structure and thermoelectric transport properties. This research should be an important reference for designing spin caloritronic and thermoelectric devices. [ABSTRACT FROM AUTHOR]

A compact online proton spectrometer based on a CMOS plate detector was proposed for the diagnosis of picosecond intense-laser accelerated protons. Inside the CMOS plate detector, a composite structure that composed of a scintillator screen, a fiber optic plate (FOP), and a CMOS sensor was designed to detect the protons safely and efficiently. The scintillator screen converted the incident protons to visible light, which, in turn, was collected by using the FOP and detected by using the CMOS sensor. An additional aluminum housing was designed to decrease the strong electromagnetic pulse (EMP) impact on the electronic readout system from picosecond laser–plasma interaction. This online spectrometer is compact and cost-effective than the system based on the micro-channel plate or scintillator screen in combination with an electron multiplying CCD camera and has better resistance to radiation damage than the system based on a single CMOS sensor. [ABSTRACT FROM AUTHOR]

Millimeter wave systems based on powerful gyrotron can deliver megawatt microwave power, which is an important auxiliary heating method for magnetic confinement fusion devices. Reflective gratings are normally used as quasi-optical polarizers for polarization control of the wave in such systems. Based on the coordinate transformation method, we developed a numerical code to study the broadband polarization strategy. By considering the synthesis of two polarizers, we designed a pair of polarizers in the W band. Calculation results indicated that almost arbitrary polarization can be achieved in a wide frequency range. To verify the design, we set up a low-power test platform and experiments were carried out. The performance of the polarizers was tested from 80 to 105 GHz with a step of 5 GHz. The test results agreed well with the numerical results, indicating that the design is reasonable. With the development of multi-frequency gyrotrons, the study in this paper can be used as a reference for the design of broadband polarizers of multi-frequency millimeter wave systems. [ABSTRACT FROM AUTHOR]

The irradiation of a target with high laser intensity can lead to self-generation of an intense magnetic field (B-field) on the target surface. It has therefore been suggested that the sheath-driven acceleration of high-energy protons would be significantly hampered by the magnetization effect of this self-generated B-field at high enough laser intensities. In this paper, particle-in-cell simulations are used to study this magnetization effect on sheath-driven proton acceleration. It is shown that the inhibitory effect of the B-field on ion acceleration is not as significant as previously thought. Moreover, it is shown that the magnetization effect plays a relatively limited role in high-energy proton acceleration, even at high laser intensities when the mutual coupling and competition between self-generated electric (E-) and B-fields are considered in a realistic sheath acceleration scenario. A theoretical model including the v × B force is presented and confirms that the rate of reduction in proton energy depends on the strength ratio between B- and E-fields rather than on the strength of the B-field alone, and that only a small percentage of the proton energy is affected by the self-generated B-field. Finally, it is shown that the degraded scaling of proton energy at high laser intensities can be explained by the decrease in acceleration time caused by the increased sheath fields at high laser intensities rather than by the magnetic inhibitory effect, because of the longer growth time scale of the latter. This understanding of the magnetization effect may pave the way to the generation of high-energy protons by sheath-driven acceleration at high laser intensities. [ABSTRACT FROM AUTHOR]

Recently, a new kind of distributed element superconducting resonators with granular aluminum (grAl) has been developed for circuit quantum electrodynamics. Given that lumped element resonators possess certain advantages over the distributed element ones, in this paper, we use a relatively simple micro-nanotechnology, without the etching process, to fabricate the designed lumped element superconducting grAl resonators. They are deposited on silicon substrates by DC magnetron sputtering of pure Al in an atmosphere of Ar and O2. By cryogenic microwave transmission measurements, at a temperature of 50 mK, we find that, compared with a usual Al resonator of the same size, such a device shows significantly strong nonlinearity and thus higher kinetic inductance. The noise features, quality factors, and temperature-dependence of the resonant frequencies have been investigated experimentally. It is believed that the lumped element superconducting resonators with high kinetic inductance demonstrated here could also be applied to superconducting quantum computation and photon counting in the future. [ABSTRACT FROM AUTHOR]

In this research, the evolution of the piezomagnetic field of a low carbon steel under cyclic tensile stress was investigated. The objective was to explore the correlations between piezomagnetic signal measured by a fluxgate magnetometer with progressive changes that take place during the fatigue tests. Experiments show first that the piezomagnetic hysteresis loop changes drastically with the propagation of fatigue crack. A multiscale magneto-elastic model of the piezomagnetic behavior allows secondly the experimental cycles evolution to be explained. [ABSTRACT FROM AUTHOR]

The infrared dielectric property of monoclinic BaTeMo2O9 single crystals is studied by polarized IR reflectance spectra from 20 to 1800 cm-1. Based on the modified Lorentz model, the frequencies, strengths, and dampings of TO modes as well as the orientations of the dipole momenta are determined, agreeing well with Raman spectra and results from First-principles calculation. The observed modes are visually assigned to the specific atoms' motions in the primitive cell based on the theory calculations. A large shift of the internal modes of the anion groups relative to free anion co-ordination polyhedra is observed, which can be used to indicate the distortions of co-ordination polyhedra related to the nonlinear optical properties. Further, the experimental results of the strengths of the oscillators support the elimination and splitting of degenerate modes in free regular polyhedrons. These results offer a way to evaluate the nonlinear optical properties by use of traditional IR reflectivity spectra. [ABSTRACT FROM AUTHOR]

The redshift (∼54 meV) of the photoluminescence (PL) peak energy of blue InGaN/GaN light-emitting diodes exposed to 60Co γ-rays was observed. Time-resolved PL indicates that the PL radiative time increases along with irradiation does. The temperature-dependent PL and photoreflectance techniques show that γ-ray irradiance leads to higher carrier localization energies and larger Stokes' shift, respectively. These facts suggest that the redshifts of the PL peak emission introduced by γ-ray irradiance mainly originated from the enhancement of indium fluctuation. The cathodoluminescent images of the samples before and after γ-ray irradiation are compared to verify the results. [ABSTRACT FROM AUTHOR]

Researches on the fracmemristor have aroused increasing interest in the last several years, but there are no reports on design of the discrete fracmemristor. Based on the fractional-order difference and the mathematical model of the charge-controlled memristor, the discrete fracmemristor is designed where the amount of charge is determined by a fractional-order discrete system. In the numerical simulations, it shows that the pinched hysteresis loops are observed, which imply that the proposed memristor satisfies the definition of the memristor. As an application, the fracmemristor sine map is designed, and multistability is observed regarding the initial conditions of both the memristor and system. It provides a potential model for different applications such as cellular neural networks, modulators, sensors, chaotic systems, and programmable digital circuits. [ABSTRACT FROM AUTHOR]

Temperature dependent Suns-Voc measurements are performed on four types of polycrystalline silicon thin-film solar cells on glass substrates, all of which are made by solid phase crystallization/epitaxy of amorphous silicon from plasma enhanced chemical vapor deposition or e-beam evaporation. Under the two-diode model, the diode saturation currents corresponding to n=1 recombination processes for these polycrystalline silicon p-n junction cells follow an Arrhenius law with activation energies about 0.15–0.18 eV lower than that of single-crystal silicon p-n diodes of 1.206 eV, regardless of whether the cells have an n- or p-type base. This discrepancy manifests itself unambiguously in a reduced temperature sensitivity of the open-circuit voltage in thin-film polycrystalline silicon solar cells compared to single-crystal silicon cells with similar voltages. The physical origin of the lowered activation energy is attributed to subgap levels acting either as minority carrier traps or shallow recombination centers. [ABSTRACT FROM AUTHOR]

Reactions of neutral Vn, Nbn, and Tan metal clusters (n≤=11) with CO+H2 mixed gases and CH3OH in a flow tube reactor (1–50 Torr) are studied by time of flight mass spectroscopy and density functional theory calculations. Metal clusters are generated by laser ablation, and reactants and products are ionized by low fluence (∼200 μJ/cm2) 193 nm excimer laser light. Nbn clusters exhibit strong size dependent reactivity in reactions both with CO+H2 and CH3OH compared with Vn and Tan clusters. A “magic number” (relatively intense) mass peak at Nb8COH4 is observed in the reaction of Nbn clusters with CO+H2, and CH3OH is suggested to be formed. This feature at Nb8COH4 remains the most intense peak independent of the relative concentrations of CO and H2 in the flow tube reactor. No other Nbn, Tan, or Vn feature behaves in this manner. In reactions of CH3OH with metal clusters Mn (M=V, Nb, and Ta, n=3–11), nondehydrogenated products MnCOH4/MnCH3OH are only observed on Nb8 and Nb10, whereas dehydrogenated products MnCO/CMnO are observed for all other clusters. These observations support the suggestion that CH3OH can be formed on Nb8 in the reaction of Nbn with CO+H2. A reaction mechanism is suggested based on the experimental results and theoretical calculations of this work and of those in the literature. Methanol formation from CO+H2 on Nb8 is overall barrierless and thermodynamically and kinetically favorable. [ABSTRACT FROM AUTHOR]

Neutral niobium and tantalum clusters (Nbn and Tan) are generated by laser ablation and supersonic expansion into a vacuum and are reacted in a pickup cell with various low pressure (∼1 mTorr) unsaturated hydrocarbons (acetylene, ethylene, propylene, 1-butene, 1,3-butadiene, benzene, and toluene) under nearly single collision conditions. The bare metal clusters and their reaction products are ionized by a 193 nm laser and detected by a time of flight mass spectrometer. Partially and fully dehydrogenated products are observed for small (n≤=m) and large (n>=m) neutral metal clusters, respectively, with m ranging from 2 to 5 depending on the particular hydrocarbon. In addition to primary, single collision products, sequential addition products that are usually fully dehydrogenated are also observed. With toluene used as the reactant gas, carbon loss products are observed, among which Nb8C12 and Ta8C12 are particularly abundant, indicating that the Met-Car molecule M8C12 can be formed from the neutral metal cluster upon two collisions with toluene molecules. The dehydrogenation results for low pressure reactions are compared with those available from previous studies employing flow tube (high pressure) reactors. Low pressure and high pressure cluster ion reactions are also compared with the present neutral metal cluster reactions. Reactions of unsaturated hydrocarbons and metal surfaces are discussed in terms of the present neutral cluster results. [ABSTRACT FROM AUTHOR]

Neutral vanadium, niobium, and tantalum oxide clusters are studied by single photon ionization employing a 26.5 eV/photon soft x-ray laser. During the ionization process the metal oxide clusters are almost free of fragmentation. The most stable neutral clusters of vanadium, niobium, and tantalum oxides are of the general form (MO2)0,1(M2O5)y. M2O5 is identified as a basic building unit for these three neutral metal oxide species. Each cluster family (Mm, m=1,...,9) displays at least one oxygen deficient and/or oxygen rich cluster stoichiometry in addition to the above most stable species. For tantalum and niobium families with even m, oxygen deficient clusters have the general formula (MO2)2(M2O5)y. For vanadium oxide clusters, oxygen deficient clusters are detected for all cluster families Vm (m=1,...,9), with stable structures (VO2)x(V2O5)y. Oxygen rich metal oxide clusters with high ionization energies (IE>10.5 eV, 118 nm photon) are detected with general formulas expressed as (MO2)2 (M2O5)y O1,2,3. Oxygen rich clusters, in general, have up to three attached hydrogen atoms, such as VO3H1,2, V2O5H1,2, Nb2O5H1,2, etc. [ABSTRACT FROM AUTHOR]

This paper summarizes the analysis of the influence of anisotropy on the stress-optic coefficients and the determination of the stress-optic tensor components π11-π12 and π44 using an infrared polariscope and calibration with four-point bending of thin silicon samples. Values obtained are π11-π12=9.88×10-13 Pa-1 and π44=6.50×10-13 Pa-1. A fringe multiplier was also introduced to increase the sensitivity of the infrared polariscope by up to seven times. [ABSTRACT FROM AUTHOR]

The (0,0) band of the B ²Σ[sup +]-X²Σ[sup +] transition of LaS near 726 nm has been studied at high resolution using laser vaporization/reaction supersonic free jet expansion and laser induced fluorescence spectroscopy. Spectra taken at a resolution of about 50 MHz show resolved hyperfine structure which is caused principally by the unpaired 6sσ- electron in the ground state interacting with large magnetic moment of the [sub 57][sup 139]La nucleus with nuclear spin I=7/2. The X²Σ[sup +] state of LaS is in good Hund's case (b[sub βs]) coupling, however, the upper state, B ²Σ[sup +], is close to case (b[sub βJ]) coupling. A total of 1850 rotational-hyperfine transition lines have been assigned and measured. Accurate rotational, spin and hyperfine parameters for the B ²Σ[sup +] and X²Σ[sup +] states have been obtained, which give information about the electron distribution in the molecule. [ABSTRACT FROM AUTHOR]

Provides information on a study which presented the effects of precursors and substrate materials on microstructure, dielectric properties, and step coverage of (Ba,Sr)...TiO... films grown by metalorganic chemical vapor deposition. Film composition and growth rate; Film microstructure; Summary.

With the forthcoming laser intensities (I ≥ 1023 W/cm2), synchrotron radiation in a laser-plasma interaction has attracted particular interest because it can lead to an extremely bright source of γ-rays. Here, a scheme to generate a bright γ-ray pulse with high efficiency is proposed and numerically demonstrated. Using a circularly polarized (CP) laser pulse impinged on a thin foil, a relativistic flying plasma layer is formed. With another counterpropagating CP pulse colliding with the flying layer, it is found that the electrons are efficiently accelerated in the longitudinal direction by the space-charge field. The energetic electrons interact with the counterpropagating CP pulse, producing ultra-brilliant (∼1024 photons/s/mm2/mrad2/0.1%BW) highly dense (∼270nc) femtosecond (∼5 fs) γ-ray pulses. At a moderate laser intensity of 4 × 1022 W/cm2, the fraction of laser energy transferred into the γ-ray pulse is as high as 10%, which is comparable to that previously predicted for an order of magnitude higher in laser intensity. The enhanced γ-photon emission might pave the way for its potential applications in the near future. [ABSTRACT FROM AUTHOR]

A comparable study of the microstructure and magnetic properties was performed for magnetite films deposited on (100)-oriented MgO and SrTiO3 (STO) substrates. The growth of strained high quality Fe3O4 films was confirmed by x-ray diffraction analysis and Raman spectroscopy measurements. The surface morphology and magnetic properties of the two films were found to be obviously different. Moreover, a stripelike magnetic domain structure was observed in the film on STO. Substrate-induced strain is believed to be responsible for these observations, which significantly affects the magnetic anisotropy and the magnetic coupling at the antiphase boundaries in the films. [ABSTRACT FROM AUTHOR]

A systematic investigation of the expansion dynamics of plasma plumes generated by two Q-switched Nd:YAG lasers at 1064 nm wavelength operating on a silicon target was undertaken for the inter-pulse delay times of 0, 100, 200, and 400 ns using a technique involving fast-gated intensified charge-coupled device imaging. Our results indicate that the plasmas exhibit free expansion in a vacuum environment at an inter-pulse delay time of 0 ns. With increasing inter-pulse delay time, the plasma front becomes sharpened and an interaction boundary is formed. Moreover, using the radiation intensity distribution along the plasma axis of symmetry, the formation and evolution mechanism of the plasmas generated by the double pulses was analyzed at different inter-pulse delay times. Finally, the experimental results of the expansion of the plasma core and front were compared with a radiation hydrodynamics model and a drag model, and were found to be generally in good agreement. [ABSTRACT FROM AUTHOR]

Strong coupling stimulated Brillouin backscattering (sc-SBS) in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers. Here, we report on a new regime of brillouin-based plasma amplification, producing an amplified pulse with a duration of 5 fs and unfocused intensity of 6x1017 W/cm2. The results are obtained from 2D particle-in-cell simulations, using two circularly polarized pump and seed pulse with Gaussian transverse profile, both at an intensity of 2.74x1016 W/cm2, counter-propagating in a 0.3nc plasma. The significant compression of amplified seed is achieved as a result of sc-SBS amplification as well as additional compression by the interplay between self-phase modulation and negative group delay dispersion. We show that the amplified seed retains high beam qualities since the filamentation can be prevented due to the fast compression. This scheme may pave the way for few-cycle laser pulses to reach exawatt or even zetawatt regime. [ABSTRACT FROM AUTHOR]

We have investigated the characteristic properties of Co/Fe multilayers sputtered on Ru underlayer as the field generation layer (FGL) of spin torque oscillator (STO) for microwave assisted magnetic recording. The Co/Fe multilayers exhibit large uniaxial negative anisotropy (up to ~8.7 X 106 erg/cm3), ultra-low damping constant (~0.008), and small in plane coercivity Hc (~5 Oe) that are required for stable STO precession over a wide range of applied magnetic fields and injected spin currents. The importance of Ru underlayer to achieve the above parameters has been addressed. We further show through theoretical calculations that a frequency of 30+ GHz is realistic using Co/Fe multilayers as the field generation layer in a STO comprising a perpendicularly magnetized polarizer and a planar FGL (10-nm Co/Fe multilayers) separated by a metallic spacer. [ABSTRACT FROM AUTHOR]

Two-dimensional tailoring of a proton beam is realized by a "particle lens" in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a "fountain-like" pattern when these hot electrons diffuse after propagating a distance. [ABSTRACT FROM AUTHOR]

A simple scheme to produce strong magnetic fields due to cold electron flow in an open-ended coil heated by high power laser pulses is proposed. It differs from previous generation of magnetic fields driven by fast electron current in a capacitor-coil target [S. Fujioka et al., Sci. Rep. 3, 1170 (2013)]. The fields in our experiments are measured by B-dot detectors and protonradiography, respectively. A 205 T strong magnetic field at the center of the coil target is generated in the free space at I?² of 6.85 × 1014 W cm-2 µm², where I is the laser intensity, and ? is the laser wavelength. The magnetic field strength is proportional to I?². Compared with the capacitor-coil target, the generation mechanism of the magnetic field is straightforward and the coil is easy to be fabricated. [ABSTRACT FROM AUTHOR]

Backward Raman amplification (BRA) in plasmas has been promoted as a means for generating ultrapowerful laser pulses. For the purpose of achieving the maximum intensities over the shortest distances, an envelope matching between the seed pulse and the amplification gain is required, i.e., the seed pulse propagates at the same velocity with the gain such that the peak of the seed pulse can always enjoy the maximum gain. However, such an envelope matching is absent in traditional BRA because in the latter the amplification gain propagates at superluminous velocity while the seed pulse propagates at the group velocity, which is less than the speed of light. It is shown here that, by using self-ionizing plasmas, the speed of the amplification gain can be well reduced to reach the envelope matching regime. This results in a favorable BRA process, in which higher saturated intensity, shorter interaction length and higher energy-transfer efficiency are achieved. [ABSTRACT FROM AUTHOR]

Blue organic light emitting diodes are made based on 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi) as a fluorescent emitter mixed with two charge transport hosts, 4,4′-bis(carbazol-9-yl)biphenyl and Bis[2-(2-hydroxyphenyl)-pyridine]beryllium. It is found that the device efficiency increases as BCzVBi concentration increases. An extremely high 6.1% external quantum efficiency (EQE) with Commission Internationale de L'Eclairage coordinate of (0.18, 0.31) is obtained when the BCzVBi concentration reaches 50 wt. %, which is exceedingly high above a typical 1-2 wt. % concentration for typical fluorescent emitters. The 6.1% EQE is also much higher than the expected 3% value calculated using the prevailing theorem. [ABSTRACT FROM AUTHOR]

We study the influence of gas absorption on the photovoltaic properties of carbon nanotube/Si solar cells (CSSCs). The power efficiency of CSSCs changes evidently when exposed in gas, resulting from the resistance change of carbon nanotube (CNT) by gas absorption. The performances of CSSCs degrade when they are long time exposed in air, which results mainly from excessive gas absorption. Gas desorption on CNTs is accelerated by applying a current through the cells, making recovery of efficiency. By applying a current through the cells before light illumination, CSSCs show stable efficiency at ∼10% in one month. [ABSTRACT FROM AUTHOR]

Junction temperature (JT) is a key parameter of the performance and lifetime of light emitting diodes (LEDs). In this paper, a mobile instrument system has been developed for the non-contact measurement of JTs of LED under LabVIEW control. The electroluminescence (EL) peak shift of the LED is explored to measure the JT. Commercially available high power blue LEDs are measured. A linear relation between emission peak shift and JT is found. The accuracy of the JT is about 1 °C determined by the precision of the emission peak shift, ±0.03 nm, at 3σ standard deviation for blue LED. Using this system, on-line temperature rise curves of LED lamps are determined. [ABSTRACT FROM AUTHOR]

Evidence for accumulated damage is provided by investigating the effect of etch duration on the carrier lifetime of an InGaAsP quantum well (QW) inside the InP-based photonic crystal (PhC) structures. It is found that once the quantum well is etched through, additional etching reduces the carrier lifetimes from 800 to 70 ps. The surface recombination velocity (SRV) at the exposed hole sidewalls is determined from the measured carrier lifetimes of the PhC fields with different lattice parameters. The observed variation in the SRV with etch duration also confirms the presence of accumulated sidewall damage. It increases from 6×103 to 1.2×105 cm s-1 as the etching time increases from 3 to 50 min. A geometric model based on sputtering theory and on the evolution of the hole shape is developed to explain the accumulation of sidewall damage. The model is used to estimate the number of impact events from sputtered species reaching the QW sidewalls, and the variation in the accumulated impact events with etch duration is shown to be qualitatively consistent with the experimental observations. Finally, the results suggest a new method for tailoring the carrier lifetimes in PhC membrane structures. [ABSTRACT FROM AUTHOR]

On the basis of the equivalence between the AKNS hierarchy and the cKP hierarchy with the constraint k=1, we point out that there exist two choices to keep the form of the Lax operator when we perform the gauge transformation for the AKNS hierarchy, which results in two classes of functions to trigger the gauge transformation. For the second choice, two theorems for two types of gauge transformation are established. Several new and more general forms of tau-functions for the AKNS hierarchy are obtained by means of gauge transformations of both types. The union of the two choices leads to new forms of τ-functions. We generate the AKNS hierarchy from the “free” Lax operator L[sup (0)]=∂ via a chain of gauge transformations. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the spreading of water covered by a monolayer of valinomycin on a vertical glass slide, using an apparatus for Langmuir-Blodgett film deposition. Dependence of the rate of spreading on the surfactant concentration; Instability of the spreading front; Bifurcation of fronts while forming tree-like patterns.

Epitaxial single-crystal Ge1-xMnx ferromagnetic-semiconductor films were fabricated on Ge(001) substrates by molecular beam epitaxy. All the samples are ferromagnetic and have strong magnetic anisotropy indicated by different magnetization in plane and out of plane. The electrical transport of the films obeys Efros variable range hopping law in the low temperature range. Interestingly, a negative coefficient of the ordinary Hall effect of p-type carriers was found in the variable range hopping at low temperature. Anomalous Hall effect in Ge0.949Mn0.051 film was observed below the Curie temperature, indicating the carrier-mediated intrinsic ferromagnetism. [ABSTRACT FROM AUTHOR]

This letter summarizes research on the characterization of residual stresses and electron-hole lifetimes of polycrystalline silicon sheet for photovoltaic applications. Full-field polariscopy, scanning room temperature photoluminescence, and surface photovoltage are used to characterize the polycrystalline silicon sheet. An orientation dependent stress-optic coefficient has been developed and used to extract the in-plane residual stresses from analysis of transmitted near-infrared light. The characteristics of the spatial distribution and the quantitative correlation between the residual stresses and the electron-hole lifetime are presented. [ABSTRACT FROM AUTHOR]

Structural phase transformation from multiwalled carbon nanotubes to nanocrystalline diamond by hydrogen plasma post-treatment was carried out. Ultrahigh equivalent diamond nucleation density above 1011 nuclei/cm2 was easily obtained. The diamond formation and growth mechanism was proposed to be the consequence of the formation of sp3 bonded amorphous carbon clusters. The hydrogen chemisorption on curved graphite network and the energy deposited on the carbon nanotubes by continuous impingement of activated molecular or atomic hydrogen are responsible for the formation of amorphous carbon matrix. Diamond nucleates and grows in the way similar to that of diamond chemical vapor deposition processes on amorphous carbon films. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The self-assembled two-dimensional superlattice of octanthiol-passivated Au-Ag alloy nanoparticles is reported in this letter. These nanoparticles show good composition-tunable properties. In the UV-visible spectra, the absorption peaks shifted linearly from the high-energy to the lower-energy side with increasing molar faction of Au. [ABSTRACT FROM AUTHOR]

We present a direct observation of a structural transition at molecular scale in an organic p-nitrobenzonitrile (PNBN) thin film using scanning tunneling microscopy (STM). STM images clearly show an ordered molecular structure of unrecorded regions in the films, while the PNBN molecular arrangements are disordered in the recorded regions. The current-voltage (I-V) measurements from the STM demonstrate a great increase of the conductance transition in the recorded regions after the voltage pulses. Those results suggest that the recording mechanism may be due to a crystalline structural transition, which is consistent with our previously proposed mechanism in another organic system for ultrahigh density data storage. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

When chloroaluminate (AlCl4-) serves as the electrolyte, aluminum nitride (AlN) has shown promise as a cathode material in aluminum ion batteries. However, there is currently a lack of research on the mechanisms of charge transfer and cluster intercalation between AlCl4 and AlN cathode materials. Herein, first-principles calculations are employed to investigate the intercalation mechanism of AlCl4 within the AlN cathode. By calculating the formation energies of stage-1-5 AlN-AlCl4 intercalation compounds with the insertion of individual AlCl4 cluster, we found that the structure of the stage-4 intercalation compounds exhibits the highest stability, suggesting that when the clusters begin to intercalate, it is important to start with the formation of the stage-4 intercalation compounds. In the subsequent phases of the charging process (stages 1 and 2), the stabilized structure with four inserted clusters demonstrates two characteristics: the coexistence of standing and lying clusters and the insertion of two standing clusters in an upside-down doubly stacked configuration, which further improve the spatial utilization while maintaining the structural stability. In addition, we infer that a phenomenon of coexisting intercalation compounds with mixed stages will occur in the course of the charging and discharging processes. More importantly, the diffusion barrier of AlCl4 in AlN-AlCl4 intercalation compounds decreases with the reduction of stage number, ensuring the rate performance of batteries. Therefore, we expect that our work will contribute to comprehend the intercalation mechanism of AlCl4 into the AlN cathode materials of aluminum ion batteries, providing guidance for related experimental work., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Polyyne bridges have attracted extensive interest as molecular wires due to their shallow distance dependence during charge transfer. Here, we investigate whether triplet energy transfer from cadmium selenide (CdSe) quantum dots (QDs) to anthracene acceptors benefits from the high conductance associated with polyyne bridges, especially from the potential cumulene character in their excited states. Introducing π-electron rich oligoyne bridges between the surface-bound anthracene-based transmitter ligands, we explore the triplet energy transfer rate between the CdSe QDs and anthracene core. Our femtosecond transient absorption results reveal that a rate constant damping coefficient of β is 0.118 ± 0.011 Å-1, attributed to a through-bond coupling mechanism facilitated by conjugation among the anthracene core, the oligoyne bridges, and the COO⊖ anchoring group. In addition, oligoyne bridges lower the T1 energy level of the anthracene-based transmitters, enabling efficient triplet energy transfer from trapped excitons in CdSe QDs. Density-functional theory calculations suggest a slight cumulene character in these oligoyne bridges during triplet energy transfer, with diminished bond length alternation. This work demonstrates the potential of oligoyne bridges in mediating long-distance energy transfer., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)