Near-field Coupling Effect between Individual Au Nanospheres and their Supporting SiO2/Si Substrate

Abstract

We studied the far-field optical reflection contrast spectroscopy (FORCS) properties of the following system: individual Au nanospheres (radius R) immobilized above Si substrate with different thicknesses (d) SiO 2 between them. We found that peaks in the FORCS red-shift exponentially with d decreasing. The near-field coupling between the Au nanosphere and its supporting substrate is revealed to contribute to this, while the coupling strength is demonstrated to decrease exponentially with a decay length of 0.30 in units of d/R. It qualitatively agrees well in magnitude with the near-field coupling between two noble metal nanoparticles consisting of a dimer. Our results demonstrate that the FORCS can provide insight into the near-field coupling, which is significant for their applications in nano-photonics, sensing, surfaceenhanced spectrascopies, etc.

High Order Gap Modes of Film-Coupled Nanospheres

“…[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] Due to its geometrical generality, the response of this configuration to electromagnetic wave is an interesting topic which have been studied through several theoretical approaches such 4 as single dipole approximation, 53 static approximation, 54-60 extended Mie method, [61][62][63][64][65] Green's tensor method, 66 rigorous coupled wave analysis (RCWA), 67 plasmon hybridization, [68][69][70][71] transformation optics, 72 and full-wave simulations. [73][74] For the system of film-coupled plasmonic nanoparticles, it contains a well-defined planar structure and can be easily prepared without expensive and time-consuming e-beam based nanofabrication.…”

Advanced Photonic Sciences

“…Then, to determine the decay length of the electromagnetic (EM) coupling between individual gold nanopspheres and its supporting substrate, different thicknesses (d) SiO 2 film on Si were obtained by annealing single-crystalline Si (d < 20 nm) in air or by RF sputtering SiO 2 (d > 20 nm) to serve as the substrate. (Du et al, 2010). Figure 7 illustrated the schematic diagram of the prepared gold nanospheres on SiO 2 /Si substrate samples and a typical SEM image was shown as Figure 8c.…”

“…Accordingly, the near-field EM coupling strength between them determines the magnitude of the dipolar LSP wavelength shift ( 0       ) compared to the LSP wavelength (  ) of the isolated nanosphere case. (Du et al, 2010).…”

“…Recently, optical imaging and spectroscopic studies of metal nanoarrays, individual metal nanostructures, and graphene (one monolayer thick carbon atoms packed into a two-dimensional honeycomb lattice, which is the basic building block for other sp 2 carbon nanomaterials.) sheet have attracted much attention (Du et al, 2008(Du et al, , 2010Laurent et al, 2005Laurent et al, , 2006Ni et al, 2007;Wang et al, 2010). As an example, scanning near-field optical microscope (SNOM) has provided high resolution and been widely used in nanostructure study.…”

Confocal White Light Reflection Imaging for Characterization of Nanostructures

“…Recently, optical imaging and spectroscopic studies of metal nanoarrays, individual metal nanostructures, and graphene (one monolayer thick carbon atoms packed into a two-dimensional honeycomb lattice, which is the basic building block for other sp 2 carbon nanomaterials.) sheet have attracted much attention (Du et al, 2008(Du et al, , 2010Laurent et al, 2005Laurent et al, , 2006Ni et al, 2007;Wang et al, 2010). As an example, scanning near-field optical microscope (SNOM) has p r o v i d e d h i g h r e s o l u t i o n a n d b e e n w i d e l y u s e d i n n a n o s t r u c t u r e s t u d y .…”