| Summary: | 碩士 === 國立成功大學 === 光電科學與工程學系 === 100 === This thesis is organized as followed: Chapter 1 a brief introduction to Graphene and Raman spectroscopy .In chapter2, I will introduction the research about Raman spectroscopy of Free-Standing single-layer graphene. I used Micro-Raman spectroscopy system and Polarized micro-Raman system to analyze Free-Standing single-layer graphene. In chapter3, I introduce the research about Surface Enhanced Raman Spectroscopy of Free-Standing Graphene, the SERS spectra of single- and bi-layer graphene were measured by depositing Ag nanoparticles on graphene via thermal evaporation. In chapter4, I summarized my work on the studies of characterization of free-standing Graphene.
In the studies of Raman spectroscopy of Free-Standing single-layer graphene, I used Micro-Raman spectroscopy system and Polarized micro-Raman system to analyze Free-Standing single-layer graphene. I found the Raman G-mode feature of suspended graphene is appreciably red- shifted (by 12 cm-1) compared with the supported region and the Raman 2D mode of the free-standing graphene is red- shifted (by 24 cm-1) with respect to the supported portion. I guess the red-shift phenomenon is dependent on the strain and I try to calculate the strain of the sample. After calculating found the region of suspended (~0.3%) have bigger strain than supported (~0.2%) region. Second I studied this sample using Micro- Polarized Raman system. I found that the 2D band of free-standing graphene show a strong polarization dependence. The intensity ratio of 2D to G band shows oscillatory behavior (with minima at 90。 and 270。and maxima at 0。, 180。, and 360。). This observation is a consequence of anisotropy absorption of photon near the K-point of the Brillouin zone.
In the studies of Surface Enhanced Raman Spectroscopy of Free-Standing Graphene, the SERS spectra of single- and bi-layer graphene were measured by depositing Ag nanoparticles on graphene via thermal evaporation.
(i)Single-layer graphene provides much larger SERS enhancement compared to bi-layer graphene The reason is the morphologies of Ag particle distribution density in single-layer graphene is bigger than bi-layer.
(ii) The 532 nm excitation laser provides much larger SERS enhancement compared to 633 nm excitation laser. The reason is that 532 nm was close to the surface plasmon resonance wavelength of aggregated Ag nanoparticles on graphene.
(iii) The SERS enhancement factor on supported region is bigger than suspended region. The reason is that the interference-enhanced Raman scattering (IERS) effect doesn't exist on suspended region.
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