Rapid identification of graphene flakes: alumina does it better?

Nowadays graphene is one of the hottest systems under investigation. We report a systematic investigation of the colour contrast of graphene on 50, 72 and 80 nm thick Al2O3/Si(100) and 100 and 300 nm thick SiO2/Si(100) [1]. The CC is determined by the analysis of optical microscopy images. A corresponding assignment of graphene in the single, double and trylayer phase is made with micro-Raman spectroscopy. A quantitative evaluation allows to conclude that the colour contrast between 72 nm alumina and graphene is significantly larger than the one between 300 nm silicon oxide and graphene. Moreover, to increase the visibility, the use of a red or a green light is preferable [2]. [1] Gao L. et al., ACS Nano, 2 (2008) 1625. [2] De Marco P. et al., Nanotechnology, 21 (2010) 255703.