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Nickel–cobalt layered double hydroxide (NiCo-LDH) is a promising electrode material for supercapacitors due to its high electrochemical activity. However, it easily restacks and aggregates due to its nanosheet structure, which limits the effective utilization of redox active sites. Herein, the NiCo-LDH nanosheets derived from ZIF-67 were in situ grown on the surface of a basic copper cobalt carbonate (CoCu) urchin-like skeleton and supported by nickel foam (CoCu@NiCo-LDH). The well-designed three-dimensional (3D) hierarchical nanostructure not only effectively prevents the aggregation of NiCo-LDH nanosheets, but also provides a rapid charge transport channel, which facilitates ion diffusion and electron transport, therefore enhancing the utilization of NiCo-LDH redox active sites to a greater extent. Besides, the synergistic interactions between NiCo-LDH nanosheets and CoCu nanoneedles further enrich the redox reactions and increase the electrical conductivity and reaction kinetics of the electrode at the same time. As a result, the CoCu@NiCo-LDH electrode exhibits outstanding electrochemical performance with an ultrahigh mass loading of 14 mg cm−2, including excellent specific capacitance (18.71 F cm−2 or 1346 F g−1 at 3 mA cm−2) and distinguished rate capability of 87.3% from 3 mA cm−2 to 50 mA cm−2. When the CoCu@NiCo-LDH electrode was assembled with active carbon (AC) to form an asymmetric supercapacitor (ASC), the CoCu@NiCo-LDH//AC ASCs display outstanding energy density (1.98 mW h cm−2) and power density (97.5 mW cm−2) with excellent cycling stability (86.0% initial capacitance after 5000 cycles), and could keep an LED light bulb working for 90 min after only charging for 60 s. This work provides an effective strategy for the design and application of layered double hydroxide based pseudocapacitors. [ABSTRACT FROM AUTHOR]

Aluminum (Al) ion implantation is one of the most important technologies in SiC device manufacturing processes due to its ability to produce the p-type doping effect, which is essential to building p–n junctions and blocking high voltages. However, besides the doping effect, defects are also probably induced by the implantation. Here, the impacts of Al ion implantation-induced defects on 4H-SiC MOSFET channel transport behaviors are studied using a multiscale simulation flow, including the molecular dynamics (MD) simulation, density functional theory (DFT) calculation, and tight-binding (TB) model-based quantum transport simulation. The simulation results show that an Al ion can not only replace a Si lattice site to realize the p-doping effect, but it can also replace the C lattice site to induce mid-gap trap levels or become an interstitial to induce the n-doping effect. Moreover, the implantation tends to bring additional point defects to the 4H-SiC body region near the Al ions, which will lead to more complicated coupling effects between them, such as degrading the p-type doping effect by trapping free hole carriers and inducing new trap states at the 4H-SiC bandgap. The quantum transport simulations indicate that these coupling effects will impede local electron transports, compensating for the doping effect and increasing the leakage current of the 4H-SiC MOSFET. In this study, the complicated coupling effects between the implanted Al ions and the implantation-induced point defects are revealed, which provides new references for experiments to increase the accepter activation rate and restrain the defect effect in SiC devices. [ABSTRACT FROM AUTHOR]

Transition‐metal‐ion doping is an effective method to shorten bandgap and enhance visible‐light absorption of TiO2, but there are still some serious challenges for most doping technologies, such as nonuniform doping, severe lattice damages, metal atoms agglomeration, and inactivated impurities. Herein, a simple and universal hydrothermal method is developed to realize the effective transition‐metal ions doping of TiO2 (including Fe, Co, Mn, Cu, V, and Cr). The photoelectrochemical water splitting performances of Cr‐doped TiO2 nanorods with multifarious Cr ion valence states (Cr3+ or Cr6+ ions), various Cr‐ion concentrations, with or without oxygen vacancy activation are emphatically and systematically studied. Experiments and theoretical calculations demonstrate that the remarkably enhanced carrier separation and injection efficiencies are the key factors to improve the visible‐light photoactivity, benefiting from the homogeneous distribution of impurity atoms and the incorporation of oxygen vacancies. The Cr3+‐ion‐doped TiO2 nanorod arrays with oxygen vacancy activation (Cr3+/Ov–TiO2) displays an impressive incident photon‐to‐electron conversion efficiency of 5.4% at 450 nm visible light, far superior to the pure TiO2 of 0.03%. Furthermore, no obvious photocurrent decay is observed in the Cr3+/Ov–TiO2 photoanode after 12 h continuous light illumination. [ABSTRACT FROM AUTHOR]

The strain induced piezoelectric and piezoresistive effects have been regarded as promising methods to regulate the photoelectric properties of two-dimensional transition metal dichalcogenides. However, the distinction between the influence of piezoelectric and piezoresistive effects on devices is ambiguous. Here, piezo-phototronic photodetectors based on monolayer WS2 were fabricated to investigate the competitive behavior of the piezoelectric and piezoresistive effects. We have shown that the piezoresistive effect dominates the photocurrent enhancement through narrowing the bandgap under small strain. With increasing strain, the influence of piezoelectric effect became more and more obvious, and it dominated the photo-induced carrier transport behavior through polarization charges accumulated at the metal–semiconductor contact interface when the strain exceeded 0.78%. Under the strain condition, the modulation of strain on photocurrent reached as high as 1400%. [ABSTRACT FROM AUTHOR]