Graphene-Thickness-Dependent Graphene-Enhanced Raman Scattering

• Published in: Journal of physical chemistry. C Vol. 117; no. 5; pp. 2369 - 2376
• Main Authors: Ling, Xi, Wu, Juanxia, Xie, Liming, Zhang, Jin
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 07-02-2013
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Physics; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Thin films and multilayers; Ultrathin films; Thickness; Raman spectra; Band structure; Graphene; Size effect; Molecular configurations; Vacuum deposition
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp310564d

Graphene-enhanced Raman scattering (GERS), enhancing Raman signals on graphene surface, is an excellent approach to investigate the properties of graphene via the Raman enhancement effect. In the present study, we studied the graphene-thickness dependent GERS in detail. First, by keeping molecule density on few-layer graphene using vacuum thermal deposition method, GERS enhancement was found to be the same for all graphene layers (one to six layers). While adsorbing probe molecules by solution soaking, the GERS enhancing factor was different on monolayer and bilayer graphene. By soaking in low concentration solutions, the GERS intensity on bilayer graphene was stronger than that on monolayer graphene, whereas by soaking under high concentration solutions, the GERS intensity difference was much less for that on monolayer and on bilayer. Molecule density, molecular configuration, and GERS enhancing factor are further discussed for molecules on monolayer and bilayer graphene. It was finally concluded that the abnormal graphene-thickness dependence of GERS between monolayer and bilayer graphene was attributed to the different enhancement for GERS on monolayer and bilayer graphene. Monolayer and bilayer graphene have different electronic structure and then doping effect of probe molecules, which shifts the Fermi level of graphenes differently. As a result, monolayer and bilayer graphene have different energy band matching with the probe molecules, yielding different chemical enhancement.