Characterization of Nano-Scale Graphene Devices for Thickness and Defect Metrology Using Micro and Nano- Raman Spectroscopy

Nanoscale metrology (thickness, defectivity) of carbon-based devices is a substantial challenge due to device dimension scaling. Development of graphene-based nanoelectronics required solutions for thickness and defect metrology owing to the difficulty of probing the atomic structure of individual graphene sheets. Distinguishing the number of graphene layers for a particular test structure as well as quantifying disorder for local defect characterization is essential to study graphene based devices. Raman spectroscopy has proved to be an appropriate approach in this regard for identifying and distinguishing the number graphene layers in thin (n < 4) multilayer exfoliates by signatures of the 2D Raman band. Raman spectroscopy is capable not only in establishing the registry of graphene flakes but also in identifying defects present by study of D (defect) bands. In this work we have employed Raman thickness metrology protocols with customized commercial graphene exfoliates to distinguish mono and bi layer graphene flakes deposited on test structures via analysis of the Raman 2D bands. Raman spectra of CVD graphene deposited on similar test structures have also been investigated. Defects introduced by controlled dose, e-beam irradiation have likewise been analyzed. The evolution of defect induced D bands in Raman and the I(D)/I(G) ratios are used to establish relative defect densities.