74 research outputs found
High-Performance Self-Powered Photodetectors Based on ZnO/ZnS Core-Shell Nanorod Arrays
In recent years, there is an urgent demand for high-performance ultraviolet photodetectors with high photosensitivity, fast responsivity, and excellent spectral selectivity. In this letter, we report a self-powered photoelectrochemical cell-type UV detector using the ZnO/ZnS core-shell nanorod array as the active photoanode and deionized water as the electrolyte. This photodetector demonstrates an excellent spectral selectivity and a rapid photoresponse time of about 0.04 s. And the maximum responsivity is more than 0.056 (A/W) at 340 nm, which shows an improvement of 180 % compared to detectors based on the bare ZnO nanorods. This improved photoresponsivity can be understood from the step-like band energy alignment of the ZnO/ZnS interface, which will accelerate the separation of photoexcited electron-hole pairs and improve the efficiency of the photodetector. Considering its uncomplicated low-cost fabrication process, and environment-friendly feature, this self-powered device is a promising candidate for UV detector application
Enhanced Interfacial Dzyaloshinskii-Moriya Interaction in annealed Pt/Co/MgO structures
The interfacial Dzyaloshinskii-Moriya interaction (iDMI) is attracting great
interests for spintronics. An iDMI constant larger than 3 mJ/m^2 is expected to
minimize the size of skyrmions and to optimize the DW dynamics. In this study,
we experimentally demonstrate an enhanced iDMI in Pt/Co/X/MgO ultra-thin film
structures with perpendicular magnetization. The iDMI constants were measured
using a field-driven creep regime domain expansion method. The enhancement of
iDMI with an atomically thin insertion of Ta and Mg is comprehensively
understood with the help of ab-initio calculations. Thermal annealing has been
used to crystallize the MgO thin layer for improving tunneling
magneto-resistance (TMR), but interestingly it also provides a further increase
of the iDMI constant. An increase of the iDMI constant up to 3.3 mJ/m^2 is
shown, which could be promising for the scaling down of skyrmion electronics
High Reversibility of Lattice Oxygen Redox in Na-ion and Li-ion Batteries Quantified by Direct Bulk Probes of both Anionic and Cationic Redox Reactions
The reversibility and cyclability of anionic redox in battery electrodes hold
the key to its practical employments. Here, through mapping of resonant
inelastic X-ray scattering (mRIXS), we have independently quantified the
evolving redox states of both cations and anions in Na2/3Mg1/3Mn2/3O2. The
bulk-Mn redox emerges from initial discharge and is quantified by
inverse-partial fluorescence yield (iPFY) from Mn-L mRIXS. Bulk and surface Mn
activities likely lead to the voltage fade. O-K super-partial fluorescence
yield (sPFY) analysis of mRIXS shows 79% lattice oxygen-redox reversibility
during initial cycle, with 87% capacity sustained after 100 cycles. In
Li1.17Ni0.21Co0.08Mn0.54O2, lattice-oxygen redox is 76% initial-cycle
reversible but with only 44% capacity retention after 500 cycles. These results
unambiguously show the high reversibility of lattice-oxygen redox in both
Li-ion and Na-ion systems. The contrast between Na2/3Mg1/3Mn2/3O2 and
Li1.17Ni0.21Co0.08Mn0.54O2 systems suggests the importance of distinguishing
lattice-oxygen redox from other oxygen activities for clarifying its intrinsic
properties.Comment: 33 pages, 8 Figures. Plus 14 pages of Supplementary Materials with 12
Figure
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