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We study an active modulation of surface plasmon resonance (SPR) of Au nanoparticles based on highly doped graphene in visible and near-infrared regions. We find that compared to the traditional metal SPR, the SPR of Au nanoparticles based on graphene causes a remarkable blue shift. The field intensity in the gap is redistributed to standing wave. The field intensity of standing wave is about one order of magnitude higher than the traditional model. Moreover, the SPR of Au nanoparticles can be actively modulated by varying the graphene Fermi energy. We find the maximum modulation of field intensity of absorption spectra is more than 21.6 % at λ = 822 nm and the amount of blue shift is 17.4 nm, which is about 2.14 % of the initial wavelength λ = 813.4 nm, with increasing monolayer graphene Fermi energy from 1.0 to 1.5 ev. We find that the SPR sensitivity to the refractive index n of the environment is about 642 nm per refractive index unit (RIU). The SPR wavelengths have a big blue shift, which is about 33 nm, with increasing number of graphene layers from 1 to 3, and some shoulders on the absorption spectra are observed in the models with multilayer graphene. Finally, we study the Au nanorod array based on monolayer graphene. We find that the blue shift caused by the graphene increases from 14 to 24 nm, with increasing gap g from 10 to 20 nm. Then, it decreases from 24 to 14 nm, with increasing gap g from 20 to 50 nm. This study provides a new way for actively modulating the optical and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Different defective structures of nitrogen-doped 6H-SiC single crystals were examined using a combination of laser scanning confocal microscopy (LSCM), scanning electron microscope (SEM) and KOH-KCO etching. The form, depth and size of the defects in etched silicon carbide (SiC) crystals were observed by LSCM. Using these 3D LSCM images, defective structures varying in the growth direction were observed from a side view for the first time. To study the size, depth and form of defect etch pits in detail, we observed the defect etch pits configuration in some volumes through taking 3D LSCM pictures. Information on defects obtained using this approach will be very helpful for investigation of MP and SD formation mechanism in conducting SiC substrates, as well as the observation of polytype stability in nitrogen-doped SiC crystals. [ABSTRACT FROM AUTHOR]