Surface-enhanced Raman scattering of suspended monolayer graphene

Abstract

The interactions between phonons and electrons induced by the dopants or the substrate of graphene in spectroscopic investigation reveal a rich source of interesting physics. Raman spectra and surface-enhanced Raman spectra of supported and suspended monolayer graphenes were measured and analyzed systemically with different approaches. The weak Raman signals are greatly enhanced by the ability of surface-enhanced Raman spectroscopy which has attracted considerable interests. The technique is regarded as wonderful and useful tool, but the dopants that are produced by depositing metallic nanoparticles may affect the electron scattering processes of graphene. Therefore, the doping and substrate influences on graphene are also important issues to be investigated. In this work, the peak positions of G peak and 2D peak, the I2D/IG ratios, and enhancements of G and 2D bands with suspended and supported graphene flakes were measured and analyzed. The peak shifts of G and 2D bands between the Raman and SERS signals demonstrate the doping effect induced by silver nanoparticles by n-doping. The I2D/IG ratio can provide a more sensitive method to carry out the doping effect on the graphene surface than the peak shifts of G and 2D bands. The enhancements of 2D band of suspended and supported graphenes reached 138, and those of G band reached at least 169. Their good enhancements are helpful to measure the optical properties of graphene. The different substrates that covered the graphene surface with doping effect are more sensitive to the enhancements of G band with respect to 2D band. It provides us a new method to distinguish the substrate and doping effect on graphene. PACS78.67.Wj (optical properties of graphene); 74.25.nd (Raman and optical spectroscopy); 63.22.Rc (phonons in graphene)

Fast Hydrogenation and Dehydrogenation of Pt/Pd Bimetal Decorated over Nano-Structured Ag Islands Grown on Alumina Substrates

“…This phenomenon agrees with the surface limited diffusion [34,35,36,37]. This process can be attributed to the variation of the surface diffusion coefficient with temperature [40]. Due to the differences in the chemical potentials among the Ag nanoislands, the smaller nanoislands are thermodynamically unstable and they dissolve in atoms for each fixed temperature [41].…”

A study on the correlation between the dewetting temperature of Ag film and SERS intensity

“…Moreover, with the increase of temperature, small particles are lessened and the value distribution of AgNIs diameter became more concentrated, which indicated that the substrate becomes more uniform. The changes in the AgNIs morphologies at different temperatures are completed via surface-limited diffusion 25 , 26 , which is analogous to ostwald ripening. This process can be attributed to the varying of surface diffusion coefficient with temperature 27 .…”

Single Type of Nanocavity Structure Enhances Light Outcouplings from Various Two-Dimensional Materials by over 100-Fold

“…Table compares the characteristics of the enhancement technique in this study with those of other techniques reported previously. Although the Raman/PL signals of 2D materials have been enhanced significantly in previous studies when using plasmonic nanostructures − and photonic crystal cavities, − several external disturbances (e.g., peak shifting, peak distortion) would arise, making characterization with these techniques difficult. In contrast, the thin film-based interference enhancement method appears be a superior method for increasing the light outcoupling of 2D materials because the high enhancement effect occurs without affecting the spectral properties.…”

“…Therefore, enhancing the Raman and PL signals, in other words, the light outcoupling, of 2D materials has become particularly important for detailed analyses of their fine structural characteristics. Although several techniques have been developed previously to increase the Raman or PL signals of 2D materials, − they usually disturb the external properties of the 2D materials in an unpredictable manner, making it difficult to characterize the original Raman or PL spectra. In addition, simple approaches toward enhancing both the Raman and PL emissions of a range of 2D materials have not been reported previously.…”

“…When a probe molecule approaches a plasmonic nanostructure, its Raman scattering signals or PL intensities can be enhanced effectively. Plasmonic nanostructures have also been applied to enhance the Raman/PL signals from 2D materials. − …”