Raman Spectroscopy for the analysis of graphene photonic applications

Abstract

The research project "Graphene: Photonics and Opto-Electronics, UPM-NUS Collaboration" (Process No. 2012/50259-8) to achieve its goals, is hiring new faculties, post-docs (http://www.nature.com/Naturejobs/science/) and students, and is moreover creating an attractive research environment for researchers visitors may always be present in our center. Prof. Marcos Pimenta is a renowned professional in the field of Raman spectroscopy and your visit will help us, among other things, to build this supportive environment of scientific activity. ******Prof. Pimenta will be linked directly to the project, which aims to explore the excellent optical properties of graphene, both from the point of view of basic research as the study of nonlinear optical response, as the applied perspective with the development of photonic devices and opto-electronic. For this purpose, we are building a headquarters building for MackGrafe (www.mackenzie.br/mackgrafe.html) with facilities for growth, processing and characterization of graphene-based devices. The Center is a center "brother" of Graphene Research Centre of the National University of Singapore, headed by Prof. AH Castro Neto, working in a complementary way. ******The project comprises four research lines that are still embryonic in the literature: (1) nonlinear optics and ultrafast phenomena, (2) development of saturable absorbers to generate ultra-short pulse lasers (3) development of devices and plasmonic coupling to photonic waveguides and, (4) development of integrated optical modulators for optical fibers for applications in optical communications. The success of this project depends crucially on the availability of large samples of graphene on suitable substrates, with low electrical resistance and high optical transparency, and size scales compatible with photonic and opto-electronics devices. ******In this context, Raman spectroscopy is of fundamental importance to the project, since the crystal structures of ordered and disordered carbon are especially distinguishable from the Raman spectroscopy. The Raman spectrum of graphite has an intense line around 1582 cm-1 corresponding to the fundamental vibration (first order) of tangential elongation known as G usually associated with the vibrational mode or the phonon E2G of carbon atoms sp2 and another line weaker around 2690 cm-1, designated D, corresponding to an overtone (harmonic or second order). In addition, polycrystalline graphite spectrum lines are observed in the region of 1350 cm-1 called the D ("induced disorder") and a low intensity line at 3248 cm-1 called G'. ******On the other hand, the Raman spectrum of graphene nanosheets the G line is broadened and shifted to 1595 cm-1. Simultaneously, the intensity of the D line at 1350 cm-1 substantially increases, and it changes its shape, width and position, which is attributed to the significant decrease in the size of the areas due to the crystalline structure sp2 "partially ordered" of the graphite nanosheets graphene. This effect, since it has been reported makes Raman spectroscopy used to detect the electronic structure of graphene and its dependence on the number of layers due to the double resonance Raman process. This behavior makes Raman spectroscopy a nondestructive technique fundamental in the study of graphene. ******Thus, Professor Marcos Pimenta during his visit will develop the following activities related to Raman Spectroscopy:* At the postgraduate level, will teach a course on optical properties of graphene.* Course / training on Raman characterization in graphene and nanomaterials.* Active interaction with all researchers involved in the project. (AU)