Spectroscopic and Microscopic Analysis of Graphene for Sensor Applications

As a two-dimensional material, graphene shows very good thermal and electrical conductivities, which, with its unique optical properties, makes it suitable for a variety of applications. In this study we present detailed investigations by confocal Raman and Drude model analysis of the material's changes and improvements, as it transitioned from 3D graphite to 2D graphene. Besides Raman spectral recording, which can detect single, a few, and multi-layers of graphene, confocal Raman mapping allows distinction of such domains and direct visualization of material inhomogeneity. Moreover, far-infrared transmittance measurements, which are related to electrical conductivity, demonstrate a distinct increase of conductivity with dimensionality reduction. These measurements are particularly suited to determining important material characteristics, including time constant (the inverse of the average time between two carrier-core collisions), carrier concentration, and conductivity by using a Drude-like model. Such information is valuable for developing bio-medical sensors, which is the main application envisioned for this work.