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For the purpose of introducing a high work-function layer to improve the implied voltage in asymmetric silicon-based heterojunction photovoltaic devices, molybdenum oxide (MoOx, 0 < x < 3) is applied to the device. However, besides the role of extracting holes on one side, another singularity behavior presented itself in the nonequilibrium state, i.e. a worsened photovoltaic peformance (an 'S-shape') of current density versus voltage (J–V) was revealed with an inappropriate chemical state of the MoOx film. The source of the 'S-shaped' behavior of an MoOx/a-Si: H(i)/n-Si heterojunction device was co-analyzed by x-ray photoelectron spectroscopy with depth profiling, ultraviolet photoelectron spectroscopy, current density-voltage representation, a minority carrier lifetime survey and automat for simulation of heterostructures software simulation. It was found that an amorphous SiOx interlayer was spontaneously formed during the deposition of MoOx film onto a-Si: H(i)/n-Si substrate, blocking the transport of holes. The decrease in the work-function of the MoOx layer is attributed to an oxidation reaction at the MoOx/a-Si: H(i) boundary zone, which results in the decline of hole selectivity. A rising O/Si ratio in the SiOx interlayer induces an augmentation of valence band offsets, which could be the best interpretation of the 'S-shaped' response, because of a barrier that hinders the thermionic emission of holes. Meanwhile, the thicker (>4 nm) SiOx layer leads to a lower tunneling probability for holes. The characteristic analysis of the MoOx/a-Si: H(i)/n-Si heterojunction device deepens the understanding of the hole transport mechanism of the device. [ABSTRACT FROM AUTHOR]

Threading dislocations that are of a type were observed to form locally in InGaN layers and wells containing 7%-15% indium. Direct correlations between a type dislocations and stacking faults in InGaN layers and wells were observed. The formation of these dislocations is attributed to the dissociation of Shockley partials bounding the stacking faults. [ABSTRACT FROM AUTHOR]

We report the bandgap and electronic properties of wurtzite ZnO doped with elements IIA or/and IIIA, investigated using both theoretical and experimental methods. With wurtzite ZnO co-doped with B and Mg (denoted as ZnO:[B,Mg]) grown via metalorganic chemical vapor deposition, we have observed that both the bandgap and the conductivity can be widely tunable with the doping levels. From first-principles calculations of wurtzite ZnO:Mg, we show that IIA doping elements have a great impact on the widening of the bandgap. Also, from a newly developed calculation method for investigating the electronic properties of wurtzite ZnO:Al, we have found that IIIA doping elements play an important role in tailoring the conductivity. [ABSTRACT FROM AUTHOR]

We investigated the spin-transfer switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar through micromagnetic simulation. A two-step switching hysteresis loop due to the fourfold in-plane magnetocrystalline anisotropy of Co2FeAl0.5Si0.5 layers was obtained. The simulation explains the experimental result of the resistance versus current hysteresis loop and yields good agreement with the measured critical current. Furthermore, the magnetization trajectory and magnetization distribution were shown and analyzed to elucidate the different characters of two-step switching. [ABSTRACT FROM AUTHOR]

Predicting the domain structures and properties in both bulk single crystal and thin film ferroelectrics using the phase-field approach requires the knowledge of fundamental mechanical, electrical, and electromechanical coupling properties of a single-domain state. In this work, the elastic properties and structural parameters of cubic single crystals as well as tetragonal, orthorhombic, and rhombohedral BaTiO3 single domain states are obtained using first-principles calculations under the local density approximation. The calculated lattice constants, bulk modulus, and elastic constants are in good agreement with experiments for both the cubic paraelectric phase and the low-temperature ferroelectric phases. Spontaneous polarizations for all three ferroelectric phases and the electrostrictive coefficients of cubic BaTiO3 are also computed using the Berry’s phase approach, and the results agree well with existing experimentally measured values. [ABSTRACT FROM AUTHOR]

A complete surface reconstruction takes place after a local connection between two crossed tubes is established, leading to the creation of an extended X-shaped junction constituted by topological defects with smooth negative curvature. Molecular-dynamics simulations show that the surface reconstructions occur through (1) generalized Stone-Wales transformation and (2) the movement of sp and sp3 atoms and their transformation to sp2 atoms by bond rearrangement. Based on both the principle of energy minimization and a generalized Euler’s rule, it is demonstrated that the most stable structure for X junctions contains only 12 heptagons. The annealing temperature influences the topological structure and stability of junctions. [ABSTRACT FROM AUTHOR]

The temperature- and growth-dependent Urbach band-tail characteristics in polysilicon wafers have been investigated both experimentally and theoretically for the improvement of solar cells. The band-tail parameter in polysilicon has been obtained by temperature-dependent transmission spectra, with the aid of a detailed calculation of the transmission profile. The band-tail parameter is in the range of 30-90 meV in polysilicon. A band-tail model based on the calculation of density of occupied states and the carrier-phonon interaction has been employed to analyze the temperature-dependent band-tail characteristics. It is found that the yielded structural information can be well explained by Raman measurements. We have correlated various aspects of the observed structural properties, such as the band-tail parameter, trap concentration, grain-surface charge density, and correlation length, with the conversion efficiency of the polysilicon solar cells. [ABSTRACT FROM AUTHOR]

To address the hesitancy, inconsistency and uncertainty of decision makers cognitions, linguistic interval hesitant fuzzy sets (LIHFSs) are efficient tools. This paper focuses on studying the application of LIHFSs. To do this, two correlation coefficients of LIHFSs are defined, which needn’t consider the length of elements in LIHFSs or the arrangement of their possible interval values. To address the situation where the weights of elements in a set are different and correlative, two linguistic interval hesitant fuzzy Shapley weighted correlation coefficients are defined. Considering the situation where the weight information of features/attributes is partly known, programming models to determine the optimal fuzzy measures on them are constructed, respectively. After that, an approach to pattern recognition and multi-attribute decision making with linguistic interval hesitant fuzzy information is developed, respectively. Meanwhile, illustrative examples about medical diagnosis and selecting constructors for tunnel bidding are selected to verify the application of new approaches, and comparison with a previous method is offered. [ABSTRACT FROM AUTHOR]

NiCo2S4@PPy core–shell nanotube arrays have been successfully prepared through three facile steps: solvothermal synthesis, solvothermal sulphurisation and subsequentin situelectropolymerisation of polypyrrole (PPy). Their structure and morphology were studied by XRD, FTIR, SEM and TEM. The results suggest that a thin layer of PPy with 8 nm in thickness is wrapped on the surface of NiCo2S4nanotubes. The coating PPy strong promotes pseudo-capacitance reaction of NiCo2S4nanotube arrays. NiCo2S4@PPy shows lower charge plateau and IR drop, higher discharge plateau and Coulombic efficiency. Rate performance is improved remarkably. Average specific capacitance at 24 mA cm−2is even two times that of the uncoated NiCo2S4. The galvanostatic cycling tests at 4 mA cm−2indicate NiCo2S4@PPy exhibit the highest specific capacitance of 1524 F g−1and improved capacitance retention to 78.5% after 3000 cycles. The corresponding values of the uncoated NiCo2S4nanotube arrays are only 1410 F g−1and 22%. The improved electrochemical performance is mainly attributed to unique core–shell nanotube array structure and the key assistant effect of the coating PPy which remarkably improves the conductive property of NiCo2S4long nanotubes and effectively enhances structure stability and cycling stability of NiCo2S4nanotubes. [ABSTRACT FROM PUBLISHER]