547 research outputs found
Band Structure Engineering of Interfacial Semiconductors Based on Atomically Thin Lead Iodide Crystals
To explore new constituents in two-dimensional materials and to combine their
best in van der Waals heterostructures, are in great demand as being unique
platform to discover new physical phenomena and to design novel functionalities
in interface-based devices. Herein, PbI2 crystals as thin as few-layers are
first synthesized, particularly through a facile low-temperature solution
approach with the crystals of large size, regular shape, different thicknesses
and high-yields. As a prototypical demonstration of flexible band engineering
of PbI2-based interfacial semiconductors, these PbI2 crystals are subsequently
assembled with several transition metal dichalcogenide monolayers. The
photoluminescence of MoS2 is strongly enhanced in MoS2/PbI2 stacks, while a
dramatic photoluminescence quenching of WS2 and WSe2 is revealed in WS2/PbI2
and WSe2/PbI2 stacks. This is attributed to the effective heterojunction
formation between PbI2 and these monolayers, but type I band alignment in
MoS2/PbI2 stacks where fast-transferred charge carriers accumulate in MoS2 with
high emission efficiency, and type II in WS2/PbI2 and WSe2/PbI2 stacks with
separated electrons and holes suitable for light harvesting. Our results
demonstrate that MoS2, WS2, WSe2 monolayers with very similar electronic
structures themselves, show completely distinct light-matter interactions when
interfacing with PbI2, providing unprecedent capabilities to engineer the
device performance of two-dimensional heterostructures.Comment: 36 pages, 5 figure
Hot isostatic pressing of in-situ TiB/Ti-6Al-4V composites with novel reinforcement architecture, enhanced hardness and elevated tribological properties
In this study, titanium borides reinforced Ti-6Al-4V composites have been successfully prepared by hot isostatic pressing (HIPing). The microstructure of the as-fabricated samples was investigated using X-ray diffraction technique, secondary electron microscopy and electron backscatter diffraction and the mechanical properties evaluated through micro-hardness and wear resistance measurements together with nano-indentation. It was found that during HIPing the additive particles TiB2 have transformed into TiB needles which tend to decorate at prior particle boundaries of the consolidated powder particles to form a network structure. Under the same HIPing condition, the needles became increasingly coarser and agglomerated with increased addition of TiB2. The micro-hardness of the synthesized materials increased with increased volume fraction of TiB. Nano-indentation measurement demonstrates that the TiB network structure shows much higher nanohardness than the surrounding matrix regions. The friction coefficient of the synthesized composites decreased continuously with increased volume fraction of TiB, indicating improved wear resistance. High resolution transmission electron microscopy analysis on wear debris revealed the formation of a series of oxides suggesting that chemical reaction between alloy elements and oxygen in air may have happened. It is thus believed that the wearing of the current samples is a result of both friction and chemical reaction
Efficacy and Safety of Tribendimidine Against Clonorchis sinensis
In this randomized open-label trial, tribendimidine was shown to have an efficacy comparable to praziquantel for the treatment of Clonorchis sinensis infection. Patients treated with praziquantel experienced significantly more adverse events than tribendimidine recipient
Meta-analysis of the incidence of lead dislodgement with conventional and leadless pacemaker systems
Smith-Purcell radiation from time grating
Smith-Purcell radiation (SPR) occurs when an electron skims above a spatial
grating, but the fixed momentum compensation from the static grating imposes
limitations on the emission wavelength. It has been discovered that a
temporally periodic system can provide energy compensation to generate light
emissions in free space. Here, we introduce temporal SPR (t-SPR) emerging from
a time grating and propose a generalized t-SPR dispersion equation to predict
the relationship between radiation frequency, direction, electron velocity,
modulation period, and harmonic orders. Compared to conventional SPR, t-SPR
can: 1) Provide a versatile platform for manipulating SPR emission through
temporal modulation (e.g., period, amplitude, wave shape). 2) Exhibit strong
robustness to the electron-grating separation, alleviating the constraints
associated with extreme electron near-field excitation. 3) Introduce additional
energy channels through temporal modulation, enhancing and amplifying emission.Comment: 6 pages, 3 figure
Tunable interaction-induced localization of surface electrons in antidot nanostructured Bi2Te3 thin films
Recently, a logarithmic decrease of conductivity has been observed in
topological insulators at low temperatures, implying a tendency of localization
of surface electrons. Here, we report quantum transport experiments on the
topological insulator Bi2Te3 thin films with arrayed antidot nanostructures.
With increasing density of the antidots, a systematic decrease is observed in
the slope of the logarithmic temperature-dependent conductivity curves,
indicating the electron-electron interaction can be tuned by the antidots.
Meanwhile, the weak anti-localization effect revealed in magnetoconductivity
exhibits an enhanced dominance of electron-electron interaction among
decoherence mechanisms. The observation can be understood from an
antidot-induced reduction of the effective dielectric constant, which controls
the interactions between the surface electrons. Our results clarify the
indispensable role of the electron-electron interaction in the localization of
surface electrons and indicate the localization of surface electrons in an
interacting topological insulator.Comment: 27 pages, article+supplemental materials, published in ACS Nan
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