Carrier Exchange Research Articles

Cooperative liner shipping network design by means of a combinatorial auction

Cooperation in the ocean liner shipping industry has always been important to improve liner shipping networks (LSN’s). As tight cooperations like alliances are challenged by antitrust laws, looser forms of cooperation among liner carriers might become a reasonable way to increase efficiency of LSN’s. Our goal is to facilitate a loose form of cooperation among liner carriers. Therefore, we introduce a coordination mechanism for designing a collaborative LSN based on a multi round combinatorial auction. Via the auction, carriers exchange demand triplets, i.e. orders which describe the transport of containers between ports. A standard network design problem which includes ship scheduling and cargo routing decisions is used as isolated network design problem of an individual carrier. A carrier has to solve this isolated problem repeatedly during the auction so that the carrier is able to decide which demand triplets to sell, on which demand triplets to bid, and what prices to charge. To solve these problems we propose a variable neighborhood search based matheuristic. The matheuristic addresses the isolated planning problem in four phases (construct ship cycles, modify cycles, determine container flow, and reallocate ships to cycles). Our computational experiments on a set of 56 synthetic test instances suggest that the introduced combinatorial auction increases profits on average compared to isolated planning significantly by 4%. The more diverse the original assignment of demand triplets and ships to carriers is, the higher the potential for collaboration; for 18 diverse instances, the profits increase on average by 10%.

Colloidal Mn-Doped Cesium Lead Halide Perovskite Nanoplatelets

Strong quantum confinement in Mn-doped semiconductor nanocrystals enhances dopant–carrier exchange interactions. Here, we report the synthesis and optical properties of strongly quantum confined, quasi two-dimensional, Mn-doped CsPbCl3 nanoplatelets. A room-temperature synthesis was employed to prepare the platelets with thickness 2.2 nm (4 monolayers), which is significantly smaller than the Bohr excitonic diameter of CsPbCl3 (5 nm). Efficient transfer of excitonic energy from the host to the Mn2+ dopant ions leads to a spin-forbidden 4T1–6A1 Mn d-electron emission with the highest quantum yield of ∼20% and exhibits a long lifetime of 1.6 ms. Subsequent anion exchange reactions at room temperature lead to the formation of Mn-doped CsPbBr3 nanoplatelets, with weak Mn emission. These newly developed Mn-doped cesium lead halide nanoplatelets are suitable candidates for exploring the effects of quantum confinement on dopant–carrier exchange interaction and exhibiting interesting magneto-optic properties.

Crystal face regulating MoS2/TiO2(001) heterostructure for high photocatalytic activity

Semiconductor heterostructure is usually constructed to separate carriers, and the energy band structures of component semiconductors are mainly considered to achieve the separation. However, the interface of heterostructure also has a great influence on the transmission of carriers which is always neglected. Here, we employed {001} and {101} facets of anatase TiO2 as substrate to composite with two-dimension MoS2 and compared the photocatalytic activity. The results show that MoS2/TiO2(001) composite with optimal ratio demonstrates a large enhancement of photocatalytic activity as much as 3.4 times than that of pristine TiO2 nanosheets with exposed {001} facets. As compared, P25 with main exposed surface of anatase {101} facets was composited with MoS2, and the composite only exhibits 31% boost of photocatalytic activity than pristine P25. This contrast confirmed that {001} facets of anatase TiO2 are the key to construct carrier exchange heterostructure between MoS2 and TiO2 to enhance the photocatalytic activity. The HRTEM images show that the two-dimension MoS2 grown on the {001} facets of TiO2 nanosheets to show a face-to-face contact. This contact is an ideal transmission channel for photo-induce carriers with less scattering. Moreover, due to the higher valence band compared with {101} facets, the photo-induced holes will transfer to {001} facets and finally be extracted by MoS2 for photocatalysis degradation. The strategy that employs different crystal faces to regulate heterostructure interface can also be applied in other fields such as solar cell and electron device.

Electrical control of antiferromagnetic metal up to 15 nm

Manipulation of antiferromagnetic (AFM) spins by electrical means is on great demand to develop the AFM spintronics with low power consumption. Here we report a reversible electrical control of antiferromagnetic moments of FeMn up to 15 nm, using an ionic liquid to exert a substantial electric-field effect. The manipulation is demonstrated by the modulation of exchange spring in [Co/Pt]/FeMn system, where AFM moments in FeMn pin the magnetization rotation of Co/Pt. By carrier injection or extraction, the magnetic anisotropy of the top layer in FeMn is modulated to influence the whole exchange spring and then passes its influence to the [Co/Pt]/FeMn interface, through a distance up to the length of exchange spring that fully screens electric field. Comparing FeMn to IrMn, despite the opposite dependence of exchange bias on gate voltages, the same correlation between carrier density and exchange spring stiffness is demonstrated. Besides the fundamental significance of modulating the spin structures in metallic AFM via all-electrical fashion, the present finding would advance the development of low-power-consumption AFM spintronics.

Energy Transfer between Inorganic Perovskite Nanocrystals

Cesium lead halide nanocrystals are a new attractive material for optoelectronic applications since they combine the advantageous properties of perovskites and quantum dots. For future applications in optoelectronics and photovoltaics, an efficient energy and/or carrier exchange is a necessary condition. Here, we explicitly demonstrate nonradiative energy transfer for colloidal CsPbBr3 nanocrystals. Using time-resolved optical characterization of purposefully prepared batches of nanocrystals with different sizes, we identify the energy transfer which can be driven by the concentration gradient of excited nanocrystals as well as by the bandgap energy difference. The latter process moves the energy from smaller to larger nanocrystals and opens a possibility of directional streaming of the excitation energy in these materials. The observed energy transfer is enabled in the colloids by proximity of individual nanocrystals due to clustering.

A physical-based equivalent circuit model for an organic/electrolyte interface

The aim of this work is to develop an equivalent circuit model for the metal-organic semiconductor-electrolyte structures that are typically used as transducers in biosensor devices. In particular, a perylene derivative material is implemented in the active layer of a gold-semiconductor-electrolyte stack. Our approach is extending the standard range of the bias voltages applied for devices that operate in water. This particular characterisation protocol allows to distinguish and investigate the different mechanisms that occur at the different layers and interfaces: adsorption of ions in the semiconductor; accumulation and charge exchange of carriers at the semiconductor/electrolyte interface; percolation of the ionic species through the organic semiconductor; ion diffusion across the electrolyte; ion adsorption and charge exchange at the platinum interface. We highlight the presence of ion percolation through the organic semiconductor layer, which is described in the equivalent circuit model by means of a de Levie impedance. The presence of percolation has been demonstrated by environmental scanning electron microscopy and profilometry analysis. Although percolation is much more evident at high negative bias values, it is still present even at low bias conditions. The very good agreement between the model and the experimental data makes the model a valid tool for studying the transducing mechanisms between organic films and the physiological environment.

The impact of energy barrier height on border traps in the metal insulator semicondoctor gate stacks on III–V semiconductors

We investigated the effect of a thin interfacial layer (IL) made of silicon or germanium between high-k dielectrics and III–V semiconductors on the frequency dispersion of the capacitance–voltage (C–V) curves in detail. We demonstrated experimentally that the frequency dispersion at accumulation voltage is strongly dependent on the energy barrier height (ΦB) between high-k dielectrics and semiconductors. It was revealed that the improvement of frequency dispersion for n-type III–V semiconductors with IL is attributed to the increase in ΦB realized by inserting Ge IL. Moreover, the border trap density did not necessarily decrease with IL through the assessment of border trap density using a distributed bulk-oxide trap model. Finally, we proved that it is important to increase ΦB to suppress the carrier exchange and improve high-k/III–V gate stack reliability.

Surface State Mediated Electron Transfer Across the N-Type SiC/Electrolyte Interface

Understanding the mechanisms of charge transfer across the semiconductor/electrolyte interface is a basic prerequisite for a variety of practical applications. In particular, electrically active surface states located in the semiconductor band gap are expected to play an important role, but direct experimental evidence of surface states has proven to be challenging, and further experimental studies are required to verify their influence on the exchange of charge carriers between semiconductor and electrolyte. Due to its wide band gap, chemical stability, and controllable surface termination, silicon carbide (SiC) provides an excellent model system for this purpose. In this report, we provide a fundamental electrochemical study of n-type 6H-SiC and 4H-SiC electrodes in aqueous electrolytes containing the ferricyanide/ferrocyanide redox couple. Cyclic voltammetry and impedance spectroscopy measurements are performed over a wide range of potentials to determine the energetic positions of the SiC band edges a...

Transport properties of hybrid topological superconductor devices in contact with an environment

We investigate transport properties of different realizations of one-dimensional quantum wires coupled to a number of external electrodes in terms of the full counting statistics. Focusing on the set-ups in which edge states of Majorana type are realizable we analyze the effects of the exchange of charge carriers with the environment. We find a very strong suppression of the non-local current correlations, which decay exponentially with the coupling strength and the wire length. The local properties such as transport currents and current correlations measured at individual contacts between the wire and external electrode turn out to develop asymmetry when energy-resolved. We provide a number of exact analytical solutions and discuss experimental implications of our findings.

Growth, structure, and properties of GaAs-based (GaAs)1–x–y (Ge2) x (ZnSe) y epitaxial films

The possibility of growing the (GaAs)1–x–y(Ge2)x(ZnSe)y alloy on GaAs substrates by the method of liquid-phase epitaxy from a tin solution–melt is shown. X-ray diffraction shows that the grown film is single-crystal with the (100) orientation and has the sphalerite structure. The crystal-lattice parameter of the film is af = 0.56697 nm. The features of the spectral dependence of the photosensitivity are caused by the formation of various complexes of charged components. It is established that the I–V characteristic of such structures is described by the exponential dependence I = I0exp(qV/ckT) at low voltages (no higher than 0.4 V) and by the power dependence J ~ Vα, where the exponent α varies with increasing voltage at high voltages (V > 0.5 V). The results are treated within the framework of the theory of the drift mechanism of current transfer taking into account the possibility of the exchange of free carriers within the recombination complex.

The Effect of Doping on the Electrophysical Properties of Polycrystalline Diamond Films Deposited from an Abnormal Glow Discharge

The paper is focused on the study of the boron doping effect on the electrical characteristics, on the mechanism of charge carrier transfer, and on the energy spectrum of the localized defect states in the polycrystalline diamond films (PDF) deposited from an abnormal glow discharge. PDF doping enables to form the semiconductor layers of p-type conductivity, which have as good properties as those of PDF produced by the alternative methods. The doping reduces the degree of disorder in the film material brought by the growth defects, which determine the film electrical characteristics and electrotransfer mechanism. The PDF electrical characteristics and electrotransfer mechanism are determined by the defects of different nature, whose band gap energy levels have a continuous energy distribution. A p-type activation component is realized in the exchange of charge carriers between the valence band and shallow acceptor levels with the activation energy of 0.013-0.022 eV. Doping increases the effect of the hopping mechanism of the conductivity involving the localized states with a density of (1-6)·1020 eV-1 •cm-3 distributed near the Fermi level, which is in the low half of the band gap.

Heterostructure of epitaxial (001) Bi4Ti3O12 growth on (001) TiO2 for enhancing photocatalytic activity

In this work, specific exposed crystal facets were employed to construct epitaxial heterostructure for high efficiency carriers transmission channel. The (001) face of anatase TiO2 was chosen to composite (001) Bi4Ti3O12 for two reasons. First, as the lattice spacing of (110) faces of anatase TiO2 (0.26741 nm) is very close to that of (020) (0.27240 nm) or (200) (0.27080 nm) faces of Bi4Ti3O12, (001) Bi4Ti3O12 will epitaxial grow on the (001) faces of anatase TiO2. Second, due to the high surface energy, the chemical reaction between TiO2 and Bi(NO3)3 will occur at a low Bi:Ti mole ratio to form well crystallographic Bi4Ti3O12 nanocrystals. Compared with Bi4Ti3O12/P25 composite, this epitaxial heterostructure is confirmed to be an ideal carriers exchange channel to extend the separation time of photo-induced carriers and enhance photocatalytic activity. This study demonstrates the importance of crystal facets choice of substrate for constructing high efficiency carriers transmission channel.

Influences of Ni Doping on the Morphology, Optical and Magnetic Properties of ZnO Nanostructures Synthesized by Solvothermal Process.

Pure and Ni-doped ZnO nanostructures have been synthesized by a solvothermal process. The structure, morphology and properties of as-synthesized samples have been investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), selected-area electron diffraction (SAED), UV-vis spectrometer as well as by vibrating sample magnetometer (VSM). XRD and EDS studies indicated that the as-prepared products were well-crystallized wurtzite hexagonal structure. The SEM and TEM images show that the individual Zn0.96Ni0.04O nanostructure is composed of several nanorods with average diameter of 200 nm and lengths of 500 nm. The structure and morphology analyses show that Ni doping can influence the nanostructures morphology, but cannot change the crystal structures of ZnO samples. The UV-vis spectra showed that Ni dopant can result in an appreciable blue-shift for the absorption edge of the Ni-doped ZnO samples. The band gap energy of the Zn0.96Ni0.04O nanostructure was about 3.23 eV. By magnetic measurements, it was observed that the pure ZnO nanostructure exhibits diamagnetic property while the sample of 4% Ni shows an obvious ferromagnetic behavior at room temperature due to the formation of solid solution Zn0.96Ni0.04O, sp-d and d-d carrier exchange interactions, and the presence of abundant defects and oxygen vacancies.

Two-component model for long-term prediction of threshold voltage shifts in SiC MOSFETs under negative bias stress

The negative bias temperature instability in SiC MOSFETs was investigated. Considering the time, temperature, and bias dependences of the threshold-voltage (Vth) shift, we propose a two-component model for long-term prediction. On the basis of fitting results, we discuss the origins of these components. The first component, which dominates short-term instability, was found to show reverse temperature and weak bias dependences. Such trends are consistent with the carrier exchange of pre-existing slow oxide traps, which are O vacancies. After subtracting the first component, the second component was found to show power-law time dependence, similar to that observed in Si devices. The forward temperature and strong bias dependences of the second component indicate the activation of additional traps. The activation energy of 0.1 eV is consistent with that of a Si device using nitrided gate oxide. Therefore, the origin of the long-term Vth shift of SiC-MOSFETs was suggested to be a nitrogen-related site. Control of the amount of nitrogen is expected to be important for the long-term threshold stability of SiC-MOSFETs.

Low frequency noise behaviors in the partially depleted silicon-on-insulator device

Low frequency noise in the partially depleted silicon-on-insulator (SOI) NMOS device is investigated in this paper. The experimental results show low frequency noise behaviors are in good consistence with classical noise model. Based on McWhorter model, the low frequency noise in the SOI device results from the exchange of carriers between channel and oxide. The densities of trapped charges in the front gate oxide and buried oxide are extracted. Due to the difference between manufacture processes, the extracted density of trapped charges in the buried oxide (Nt=8×1017 eV-1·cm-3) is larger than that in the gate oxide (Nt=2.767×1017 eV-1·cm-3), and the result is in good agreement with testing result of transfer characteristics in part 2. Based on the charge tunneling mechanism, the spatial distribution of trapped charges in the gate oxide and buried oxide are extracted by using the tunneling attenuation coefficient (λ=0.1 nm for SiO2) and time constant (τ0=10-10 s), and the result also proves that the trap in buried oxide is larger than that in gate oxide. In addition, the influence of channel length on the low frequency noise in the SOI device is discussed. The variations of normalized channel current noise power spectral density with channel length are investigated at four frequencies(10 Hz, 25 Hz, 50 Hz, and 100 Hz). The experimental results show that the normalized noise power spectral density decreases linearly with the increase of channel length, which indicates the low frequency noise of SOI device is mainly caused by the flicker noise in the channel, and the contribution of source/drain contact and parasitic resistances could be ignored. Finally, the dependences of back gate voltage on the front gate threshold voltage, front channel current and front channel noise are discussed by considering the charge coupling effect. The experimental results show the measured channel current and channel noise with applying front gate voltage and back gate voltage simultaneously are larger than those with applying the front gate voltage and back gate voltage separately.

Electrical and photoelectric properties of polycrystalline diamond films deposited from an abnormal glow discharge

Electrical and photovoltaic properties of polycrystalline diamond films (PDF), deposited from the abnormal glow discharge were analysed. Features of charge carrier transfer in PDF are determined by continuous energy distribution in the band gap of defect states of different nature. Dominated n-type conductivity activation component of electrical conduction and photoconductivity is complemented by a hopping mechanism with the participation of states near the Fermi level with a density 5.6·1017–2.1·1021 eV−1 cm−3. Activation transfer is realized in the exchange of charge carriers between the allowed bands and donor levels with the activation energy 0.007-0.21 eV, which are sparsely populated and have wide variation in their parameters. Trapping centers and carriers recombination are heterogeneously distributed in grain boundaries. Under lighting, the state density increases 3-5 times and probable jump length decreases by 1-3 nm. Spectral distribution centers of photosensitivity are correlated with the distribution of deep-level defects, determining the absorption spectra.

Tungsten polyoxometalate molecules as active nodes for dynamic carrier exchange in hybrid molecular/semiconductor capacitors

In this work we study the utilization of molecular transition metal oxides known as polyoxometalates (POMs), in particular the Keggin structure anions of the formula PW12O403−, as active nodes for potential switching and/or fast writing memory applications. The active molecules are being integrated in hybrid Metal-Insulator/POM molecules-Semiconductor capacitors, which serve as prototypes allowing investigation of critical performance characteristics towards the design of more sophisticated devices. The charging ability as well as the electronic structure of the molecular layer is probed by means of electrical characterization, namely, capacitance-voltage and current-voltage measurements, as well as transient capacitance measurements, C (t), under step voltage polarization. It is argued that the transient current peaks observed are manifestations of dynamic carrier exchange between the gate electrode and specific molecular levels, while the transient C (t) curves under conditions of molecular charging can supply information for the rate of change of the charge that is being trapped and de-trapped within the molecular layer. Structural characterization via surface and cross sectional scanning electron microscopy as well as atomic force microscopy, spectroscopic ellipsometry, UV and Fourier-transform IR spectroscopies, UPS, and XPS contribute to the extraction of accurate electronic structure characteristics and open the path for the design of new devices with on-demand tuning of their interfacial properties via the controlled preparation of the POM layer.

Theory to carrier recombination in organic disordered semiconductors

A theoretical description for recombination kinetics of charge carriers in a disordered system with a broad energy distribution of localized states (DOS) is suggested. This kinetics is governed by the exchange of carriers between transport states and traps. Concentration transients in systems with Gaussian DOS, typical for organic semiconductors, appear much steeper than those obtained for systems with exponential DOS. This difference in recombination kinetics is caused by the difference in thermalization kinetics for these two types of the DOS functions. The comparison of the recombination transients for mobile and trapped carriers in exponential and Gaussian DOS might help to distinguish between these two possible shapes of the DOS using experimental data for transient photoconductivity and photoabsorption.

Optical signatures of a fully dark exciton condensate

We propose optical means to reveal the presence of a dark exciton condensate that does not yield any photoluminescence at all. We show that i) the dark exciton density can be obtained from the blueshift of the excitonic absorption line induced by dark excitons; ii) the polarization of the dark condensate can be obtained from the blueshift dependence on the probe photon polarization as well as from the Faraday effect. All these effects result from carrier exchanges between dark and bright states.

Gate dielectric degradation: Pre-existing vs. generated defects

We consider the possibility that degradation of the electrical characteristics of high-k gate stacks under low voltage stresses of practical interest is caused primarily by activation of pre-existing defects rather than generation of new ones. In nFETs in inversion, in particular, defect activation is suggested to be associated with the capture of an injected electron: in this charged state, defects can participate in a fast exchange of charge carriers with the carrier reservoir (substrate or gate electrode) that constitutes the physical process underlying a variety of electrical measurements. The degradation caused by the activation of pre-existing defects, as opposed to that of new defect generation, is both reversible and exhibits a tendency to saturate through the duration of stress. By using the multi-phonon assisted charge transport description, it is demonstrated that the trap activation concept allows reproducing a variety of experimental results including stress time dependency of the threshold voltage, leakage current, charge pumping current, and low frequency noise. Continuous, long-term degradation described by the power law time dependency is shown to be determined by the activation of defects located in the interfacial SiO2 layer of the high-k gate stacks. The findings of this study can direct process optimization efforts towards reduction of as-grown precursors of the charge trapping defects as the major factor affecting reliability.