A binder‐free supercapacitor electrode of NiCo2O4 nanograss coated on nickel foam (NF) was prepared by single‐mode microwave method along with calcination, displaying a higher specific capacitance (1042 F/g at 1 mV/s). Furthermore, we demonstrate excellent electrochemical performance of NiCo2O4 nanograss as anode electrode and carbide‐derived carbon as cathode electrode. The resultant asymmetric supercapacitors possess high specific capacitance (105.6 F/g at 1 mV/s), good cycling stability (retention capacitance of 78.5% after 5000 cycles), high energy density (32.9 Wh/kg) and large power density (970.1 W/kg), which has potential application in energy storage devices.
Optical confinement in ZnO crystal was observed by O(+) implantation with different MeV energies and doses. Planar optical waveguides were formed in the as-implanted ZnO samples. The optical properties of the planar waveguide were investigated by the prism-coupling and the end-face coupling methods at the wavelength of 633 nm. The crystal lattice damage in the guiding region caused by the O(+) ions implantation was analyzed by the Rutherford backscattering/Channeling technique, results show that even high dose at 2 × 10(15) ions/cm(2) can hardly produce defect in near surface of ZnO. A theoretical model is developed to explain the principle of waveguide formation in ZnO crystal and the refractive index profile in the implanted waveguide was reconstructed accordingly. The experimental result and analysis are significant for application of ZnO crystal, especially for the design of ZnO light emitter devices.
A theoretical model is developed to evaluate the roles of various mechanisms, including the molar polarization and molar volume, the spontaneous polarization and the photoelastic effect, for the modifications of refractive indices in ion-implanted LiNbO3 waveguides. Based on the model, numerical calculations of refractive indices as a function of the lattice damage level in LiNbO3 crystals of different crystalline orientations (X, Y, and Z), are performed, with results in a good agreement with experimental data. The analysis indicates that the spontaneous polarization, the molar polarization, and molar volume play important roles in determining the index profiles in ion implanted LiNbO3. In addition, the contribution of the strain-induced photoelastic effect has been identified for different damage levels.
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