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A heterojunction photodiode was fabricated from Bi doped Cs2SnCl6 nanoparticles (Cs2SnCl6:Bi NPs) spin-coated on an epitaxially grown GaN substrate. With the back illumination configuration, the heterojunction photodiode demonstrated excellent narrow-band UV sensing capability with a full wavelength of half maximum of 18 nm and a maximum detectivity of 1.2 × 1012 jones, which is promising for biomedical applications. In addition to the excellent narrow band UV sensitivity, the device also demonstrated a large linear dynamic range of 71 decibels (dB) and a fast photoresponse speed (a rise time of 0.75 μs and a fall time of 0.91 μs). The excellent performance is attributed to excellent carrier separation efficiency at the heterojunction interface and improved carrier collection efficiency through the multi-walled carbon nanotube (MWCNT) network. All the above advantages are of great importance for commercial deployment of perovskite-based photodetectors. [ABSTRACT FROM AUTHOR]

High quality ZnO–TiO 2 core–shell nanowires (NWs) have been fabricated via a facile two-step method: growth of ZnO nanowires by hydrothermal synthesis and then coating of highly uniform TiO 2 shell using atomic layer deposition (ALD) technique. The ultraviolet (UV) emission intensity of the ZnO–TiO 2 core–shell NWs is largely quenched due to an efficient electron–hole separation that reduces the band-to-band recombinations. To the contrary, the absorption of the ZnO–TiO 2 core–shell NWs in both UV and visible region is enhanced, which is attributed to the antireflection properties of the TiO 2 shell. An UV photodetector fabricated from the ZnO–TiO 2 core–shell NWs showed a maximum photoresponsivity as high as 495 A/W at 373 nm under −10 V, which is ∼8 times higher than that of the photodetector fabricated from bare ZnO NWs. In addition, the transient response of the ZnO–TiO 2 core–shell NWs is improved by 6 times as compared to that of the bare ZnO NWs. The results presented in this work suggest that ZnO–TiO 2 core–shell NWs may be promising for various optoelectronics applications including: UV photodetectors, optical switches, optical fibers and solar cells. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel 3D WO3 nanoshale structure was synthesized via hydrothermal method. [•] The 3D WO3 nanoshale demonstrated good photoresponsivity in the UV region. [•] The 3D WO3 nanoshale may be promising for various optoelectronic applications. [ABSTRACT FROM AUTHOR]

Abstract: ZnO quantum dots-graphene (QDs-graphene) composite was synthesized using atomic layer deposition method. A photodetector fabricated from the ZnO QDs-graphene composite and polymers demonstrated high sensitivity to UV light with a maximum photoresponsivity of 247A/W at 325nm. The high photoresponsivity of this device is attributed to the high active surface to volume ratio of the ZnO QDs-graphene composite. In addition to the high photoresponsivity, fast transient response with response time on the order of tenth of milliseconds was achieved, which is attributed to high carrier transport and collection efficiency through the graphene. [Copyright &y& Elsevier]

Abstract: The ZnO/graphene nanocomposite was synthesized by high energy ball milling and evaluated as an anode material for lithium-ion batteries. EDX elemental mapping indicated that graphene was dispersed homogeneously in the ZnO matrix. The nanocomposite exhibits an initial reversible capacity of 783mAh/g and maintained a capacity of 610mAh/g after 500cycles at 100mA/g. Moreover, it shows excellent rate capability and cycling stability even at 10,000mA/g, which can be attributed to the unique structure and the synergistic effect between the nanosized ZnO and graphene. [Copyright &y& Elsevier]

A high sensitivity, fast ultraviolet (UV) photodetector was fabricated from WO3 nanodiscs (NDs)/reduced graphene oxide (RGO) composite material. The WO3 NDs/reduced GO composite material was synthesized using a facile three-step synthesis procedure. First, the Na2WO4/GO precursor was synthesized by homogeneous precipitation. Second, the Na2WO4/GO precursor was transformed into H2WO4/GO composites by acidification. Finally, the H2WO4/GO composites were reduced to WO3 NDs/RGO via a hydrothermal reduction process. The UV photodetector showed a fast transient response and high responsivity, which are attributed to the improved carrier transport and collection efficiency through graphene. The excellent material properties of the WO3 NDs/RGO composite demonstrated in this work may open up new possibilities for using WO3 NDs/RGO for future optoelectronic applications. [ABSTRACT FROM AUTHOR]

Abstract: An experimental study of the optical properties of PVA coated In2O3 nanoparticles was performed with characterization methods including photoluminescence, absorption and point source, photogenerated current–voltage measurements. The photoluminescence results show that PVA can suppress the parasitic green emission by modifying defect energy states introduced by oxygen vacancies. Thin films fabricated from PVA coated In2O3 nanoparticles show higher photocurrent and suppressed dark current, which may be promising for UV photodetector applications. [Copyright &y& Elsevier]

Abstract: A near ultraviolet (UV) photodetector is fabricated from colloidal In2O3 nanoparticles coated with polyvinyl-alcohol (PVA). The device exhibits lower dark current and higher responsivity compared with a photodetector fabricated from uncoated In2O3 nanoparticles. The rise and fall time of the PVA coated photodetector is about 500s and 1600s, respectively, one half of the uncoated device. The faster response time of the PVA enhanced photodetector is due to surface passivation which reduces the surface defects while enhancing desorption of oxygen from the nanoparticle surface, thus increasing free carrier concentration. [Copyright &y& Elsevier]

Enhanced near band gap edge (NBE) emissions of PVA–ZnOnanoparticleswere achieved by employing SiO2–Au core/shell nanostructureswhereas the defect-level emission (DLE) is greatly suppressed. A maximumenhancement of nearly 400% was observed using SiO2–Aufor the emission with optical resonance at 554 nm. SiO2–Au core/shell nanostructures also show a superior tunabilityof resonance energy as compared to that of the pure metal nanoparticles.The enhancement of the NBE emission and suppressed DLE is ascribedto the transfer of the energetic electrons excited by surface plasmonfrom metal nanoparticles to the conduction band of ZnO nanoparticles. [ABSTRACT FROM AUTHOR]

An ultraviolet heterojunction photodiode consisting of epitaxially grown p-GaN layers and polyvinyl alcohol coated ZnO colloidal nanoparticles exhibits a lowpass and bandpass alternative property depending on the illumination direction. At 0 V bias, a time response on the order of 10 s of milliseconds was demonstrated with a responsivity on the order of mA/W with about 100 nW of ultraviolet illumination. The rectification ratio at ±5 V was 1000 under dark environment. Deposition of colloidal ZnO nanoparticles on an independent p-GaN substrate introduces a technique to create a heterostructure pn junction photodiode with wavelength selection by back illumination. [ABSTRACT FROM AUTHOR]

A heterojunction photodiode was fabricated from multiwalled carbon nanotubes (MWCNTs)/ZnO nanowires/p-Si (100) substrate composite structure. The heterojunction photodiode demonstrated a faster transient response and higher responsivity than the reference sample without deposition of MWCNTs, which is attributed to improved carrier collection and transport efficiency through the MWCNTs network. The high photoresponsivities of the devices are explained in terms of operation as a hybrid of photodiode and photoconductor modes. The spectral response of the devices showed dependence on voltage polarity and is attributed to the high valance band offset in the interfacial region of ZnO and p-Si substrate. [ABSTRACT FROM AUTHOR]

A heterojunction photodiode was fabricated from ZnO nanowires (NWs) grown on a p-type Si (100) substrate using a hydrothermal method. Post growth hydrogen treatment was used to improve the conductivity of the ZnO NWs. The heterojunction photodiode showed diode characteristics with low reverse saturation current (5.58 × 10-7 A), relatively fast transient response, and high responsivity (22 A/W at 363 nm). Experiments show that the photoresponsivity of the photodiode is dependent on the polarity of the voltages. The photoresponsivity of the device was discussed in terms of the band diagrams of the heterojunction and the carrier diffusion process. [ABSTRACT FROM AUTHOR]

In this article, an integrated drive converter of segmented double-stator switched reluctance machine (SDS-SRM) with isolation and nonisolation charging capabilities for electric vehicle (EV) is presented. The proposed converter can not only reduce the number of the power switches, but also implement multiple operation modes. In nonisolation charging mode, the motor windings and existing power switches constitute a buck/boost converter to charge the battery. The appropriate rotor positions are obtained to achieve torque-free control, and the interleaved phase currents control method is introduced to reduce the charging current ripples. In isolation charging mode, the inner-stator is powered by the utility grid to drive the middle-rotor, and converts electrical energy into mechanical energy, while the outer-stator is operated in generation mode to convert mechanical energy into electrical energy. The SDS-SRM is served as a rotating transformer to transfer the electric power to charge the battery with the galvanic isolation function. A low power proof-of-concept prototype platform is built and experiments are carried out to verify the effectiveness of the proposed integrated drive converter and the corresponding control schemes. [ABSTRACT FROM AUTHOR]

The Bengal Fan is a mud-rich, deep-water sediment system. A series of recently discovered biogenic gas reservoirs in the northeastern Bay of Bengal are fine-grained. The Pliocene gas discovered in the study area accumulated in the levee element of a deep-water channel complex identified by high-resolution three-dimensional (3D) seismic interpretation integrated with well logs and sidewall cores (SWC). The thickness and porosity of the levee gas reservoir are of good quality, but the permeability is relatively low owing to the high mud content. The discovery of the levee sandstone indicates various reservoirs in this mud-rich sediment system. Moreover, gas discovery implies that the gravity-flow sediment systems "link" the source rock in the study area. Gas reservoirs were discovered in Pliocene gravity-flow sediment systems, where the palaeo-climate experienced significant changes with a dramatic increase in total organic carbon (TOC) from the Miocene to the Pliocene. TOC-rich pelagic mudstones and deep-water gravity sediments act as source rocks for petroleum systems. Therefore, gravity-flow sediment systems have developed self-accumulating petroleum plays that exhibit enormous potential for exploration. Given the structural framework in the northeastern part of the Bay of Bengal, stratigraphic or structure-stratigraphic traps could have developed in the Pliocene deep-water sediment systems in the Bengal Fan. • Fine-grained deep-water turbidite gas reservoirs in upper Bengal Fan. • Bengal Fan is with Pliocene deep-water sediment systems. • Stratigraphic or structure-stratigraphic traps for exploration. • A close relationship between petroleum and deep-water gravity systems. [ABSTRACT FROM AUTHOR]

Photoresponse from multicolor photodetector was measured in the spectral range of 0.4–6.0 μm as a function of temperature and bias voltage. Devices were fabricated from wafers with an active region of five periods of GaAs quantum rings grown by droplet epitaxy technique on lattice matched Al0.3Ga0.7As barriers. The photoresponse spectra exhibit two broad bands in the visible-near-infrared and midinfrared spectral regions. The visible-near-infrared band, which is due to interband transitions, was observed at temperatures as high as room temperature. On the other hand, the midinfrared band, which is due to intersubband transitions, was observed at temperature lower than 80 K. [ABSTRACT FROM AUTHOR]

The characteristics and evolution of different types of channel-complex sets (CCSs) have long attracted attention from both academia and the oil industry. 3D seismic data from the world's largest submarine fan in the Bay of Bengal allow the exploration of morphology, architecture, and evolution of a Pleistocene submarine channel system from inception to abandonment. Four types of architectural elements are recognized, including feeder and distributary channel-complex set (CCS), levees, bend cutoffs, and incised and unincised crevasse splays. Three types of CCSs are recognized: (1) erosional non-leveed CCSs with the lowest values of channel width (W), thickness (T), and cross-sectional area (C a) (mean values of W = 153 m, T = 20 m, and C a = 2613 m2); (2) graded CCSs with the highest values of W , T and C a (mean values of W = 745 m, T = 89 m, and C a = 49183 m2); (3) aggradational leveed CCSs with intermediate values of W , T and C a (mean values of W = 476 m, T = 56 m, and C a = 21968 m2). Graded CCSs and aggradational leveed CCSs have overbank levees, crevasse splays and bend cutoffs, whereas erosional non-leveed CCSs lack these features. Such architectural difference in overbank deposits suggests a channel evolution pattern of initial incision (erosional non-leveed CCSs) and then aggradation (graded and aggradational leveed CCSs), resulting in a pattern of incision-to-aggradation channel evolution. An increase-then-decrease in channel morphometrics (represented by W , T , and C a) from erosional non-leveed CCSs with the lowest mean values of W , T , and C a , to graded CCSs with the highest mean values of W , T , and C a , and finally to aggradational leveed CCSs with the intermediate mean values of W , T , and C a suggest that the incision-to-aggradation channel evolution is related to waxing-then-waning energy cyclicity. Submarine channel turbidity flows during the waxing energy phase became progressively more energetic and increasingly more erosional, producing erosional non-leveed CCSs. Instead, submarine channel turbidity flows during the waning energy phase were more diluted and increasingly more depositional, thereby producing aggradational leveed CCSs. The phase of peak environmental energy was most likely accompanied by most energetic turbidity currents, resulting in graded CCSs. Results and observations from the current study contribute to a better understanding of architectural complexity and evolution of submarine channels. • Channel morphometrics increase-then-decrease from erosional CCSs, to graded CCSs, and finally to aggradational CCSs. • Graded and aggradational CCSs have overbank levees, crevasse splays and bend cutoffs, but erosional CCSs don't. • Channel evolution from erosion, to gradation, finally to aggradation was related to a waxing-then-waning energy cyclicity. [ABSTRACT FROM AUTHOR]

Avulsions and splays of submarine channels are important autogenic responses affecting sediment distribution in deep-water areas; however, their formation and development are still not well understood. Using high-resolution 3D seismic data and spectral decomposition red–green–blue (RGB) color blends, two seismically well-imaged submarine channel systems (SCS1 and SCS2) on the northeastern Bengal Fan are used to document the formation and development of avulsions and splays. The results suggest that avulsions occur mainly during the early evolution stage of submarine channel systems. SCS1 and SCS2 are respectively accompanied by one and four avulsions and accordingly produce two and five independent submarine channels. During this early phase, these channels collectively incise into the underlying stratigraphy but lack levee deposits. Splays, in contrast, develop consistently during the late evolution stage of the submarine channel systems. Three crevasse splays and three overbank splays develop on the overbank areas of SCS1 and SCS2. During that late stage, channel and levee deposits build over the site of former erosion, thus forming the aggradational phase of channel evolution. Crevasse and overbank splays are two different types of splays observed on this part of the Bengal Fan. The former are created by flow breaching of the adjacent levees, producing large-scale elongated shapes; they are related to relatively stable sediment gravity flows, a high-degree of channel instability, and steep levee topography. Overbank splays, however, are created by flow overtopping adjacent levees and produce small-scale, fan-like shapes; they are related to gradually-weaking sediment gravity flows, a low-degree channel unstability, and gentle levee topography. • Avulsions and splays are integral components of submarine channel evolution. • Splays of crevasse and overbank types are highlighted in this study. • Three main factors affect the formation of crevasse and overbank splays. [ABSTRACT FROM AUTHOR]

As very common deep-water phenomena, submarine channel avulsions have been paid considerable attention recently. The differences among them are, however, rarely noted, nor their relationship to the evolution of submarine channels. A seismically well-imaged channel-levee system from the Pliocene Bengal Fan, named target channels (TCs) and consisting of three independent channels (Tc1-Tc3), has been selected as a case to address these issues. Using high-resolution 3D seismic data along with spectral decomposition and RGB color blending techniques, this study images TCs from initiation to abandonment and recognizes three different types of avulsion events: regional avulsion, local avulsion and bank crevasse. In the early evolution stage of TCs, the regional avulsion and the local avulsion successively occurred, promoting TCs to obtain a stable flow course and then undergo a significant evolution. Moreover, coupled with those regional and local avulsion events, TCs were growing respectively in the form of individual channel and amalgamated stacking. In the late evolution stage of TCs, only bank crevasses occurred and led to the formation of crevasse splays in the overbank setting, which coincided with the aggradational stacking of TCs developing. This new evolution model of channel-levee systems, which acknowledges different avulsion events, may provide insights on the understanding of analogue deep-water deposits and in turn can be applied to guide the hydrocarbon exploration and development. • Three different types of avulsions are recognized in deep-water channels. • Regional and local avulsions occur in the early stage and correspond to the individual channel and amalgamated channel. • Bank crevasses occur in the late stage and develop in the aggradational channel system. [ABSTRACT FROM AUTHOR]

This study uses 3D reflection seismic data to investigate how sediment gravity flows contribute to the evolution of the lower continental slope of the Myanmar margin that is part of the Bengal Fan, the largest deep-water fan system in the world. Seafloor and subseafloor data show large sediment wave fields that developed on both flanks of an extensive submarine canyon. The sediment waves exhibit asymmetric stoss and lee sides, wave lengths and heights of 850–3000 m and 25–70 m, respectively, and an upslope direction of migration. Seismic data reveals the presence of multiple fields of vertically stacked sediment waves, interbedded with units characterised by a chaotic seismic facies that accumulate mainly in the troughs of the sediment waves and can be tracked laterally to the adjacent canyons. According to their seismic facies, geometry, and internal architecture these chaotic units are interpreted as debrites. Seismic attributes extracted from different horizons indicate that the sediment waves are dominated by fine-grained sediment, while the debrites are probably associated with coarser-grained deposits. The debrites fill the troughs of the sediment waves, as well as the downstream portions of canyon thalweg, thus flattening the paleo-seafloor. The sediment waves are interpreted as cyclic steps formed by low-density turbidity currents flowing across the slope down to the basin floor, where the change in gradient favours the formation of hydraulic jumps and the transition from supercritical to subcritical flow conditions. A conceptual model for the sediment wave evolution was proposed for the study area, in the transitional environment on the lower slope, with low-density gravity flow deposits and high-density debris flow deposits alternatively accumulating on the major gravity flow conduits. • Gravity flow deposits and associated bedforms in the Upper Bengal Fan are studied. • Seismic data revealed multiple vertically stacked fields of sediment waves. • High-density flows are confined to the canyon thalweg. • The sediment waves were most likely formed by low-density turbidity currents. • Debris flows fill the troughs of sediment waves. [ABSTRACT FROM AUTHOR]

The theoretical model of turbidite bedform evolution has been verified based on laboratory tests and outcrop surveys. However, the evolution of the bedforms associated with flow regime variation within the channel–lobe transition zone (CLTZ) is poorly documented and generally extremely poorly understood. In this study, a combination of seismic sedimentological and topographic analyses, based on high-resolution 3D seismic data within the Qiongdongnan Basin of the South China Sea, was used. Continuous bedforms varied with the depositional elements within the CLTZ of the Huaguang leveed channel system along the flow direction. The depositional elements within the CLTZ change from the main channel to the distributary channels as well as to the sub-distributary channels. Numerous bifurcation and confluence points of gravity flows illustrated the complexity of the drainage network within the CLTZ. The average asymmetry index of the bedforms increased from 0.8 to 1.6, with the average wavelength increasing from 803 m to 1545 m along the thalweg of the channels. Crevasse splays at the starting reach of the CLTZ are likely to form the initial state of the new CLTZ in the future, because the slope gradient starting from the avulsion point was higher than that inside the channel. The deep scours at the bifurcation points and high steps at the confluence points demonstrate the critical roles of supercritical flows and hydraulic jumps in reworking the bedforms of the CLTZ. The high steps at confluence points were simultaneously formed along the margin and thalweg of the main channel. The acceleration mechanisms of flow velocity forming the high steps were the increase of the elevation difference along the internal slope of the main channel margin and promotion of discharge along the main channel thalweg. This paper presents newly completed deepwater observations of the present seafloor bedforms based on the turbidity currents within the CLTZ. These observations update the evolution model of local supercritical flows and hydraulic jumps under the global decreasing trend of the Froude numbers within CLTZs. [ABSTRACT FROM AUTHOR]

A number of unidirectionally migrating channels have been interpreted as the result of the interaction between turbidity flows and bottom currents. Based on the analysis of the morphology and internal architecture of channels, different conceptual models of unidirectionally migrating channels were built to reveal the flow process of the interaction between turbidity flows and bottom currents. Most previous studies mainly focused on the straight section of channels, however, the relevant models did not elucidate the flow process in sinuous sections, limiting the knowledge on the formation mechanism and evolution of the whole unidirectionally migrating channels. By using 3D seismic data, the current study not only depicted the geomorphology and internal architecture of a sinuous unidirectionally migrating channels in the Rovuma Basin, offshore Mozambique, but also quantitatively analyzed the flow processes in the straight and bend sections of the channels. The results show that the interaction between turbidity flows and the northward-flowing Antarctic Bottom Water (AABW) led to the unidirectional migration of the turbidite channels. In the straight section of channels, fine-grained material from the upper parts of turbidity flows was deflected northward via flow stripping induced by the AABW, and this material was finally deposited as sandy lateral accretion packages and muddy drifts. The lateral deposits steepened northern channel banks and forced the southward migration of channel axes. However, in the bend section of channels, the upper parts of turbidity flows were forced towards the inner (southern) bank due to the helical flow induced by centrifugal forces, which probably offset the effect of the AABW, and therefore no lateral drifts developed. The effect of bottom currents on turbidity flows is related to the relative direction of turbidity flow and bottom currents. The lateral deposition and corresponding erosion induced by bottom currents influence the formation of the unidirectionally migrating channels, and the channels migrate towards the erosional side but away from the lateral deposition. Our results can help reveal the complete flow processes and sedimentation in the unidirectionally migrating channels in deep water basins around the world. • The flow process in sinuous unidirectionally migrating channels was analyzed. • The channels in the Rovuma Basin were affected by north-flowing bottom currents. • The effect of bottom currents was offset by centrifugal forces in bend sections. • Channels migrate towards the side of erosions induced by bottom currents. [ABSTRACT FROM AUTHOR]

Graphene fibers are fabricated by wet-spinning an aqueous large-size and small-size graphene oxide (GO) dispersion in a rotating Me3N(C16H33)Br or CaCl2 coagulation bath. [ABSTRACT FROM AUTHOR]