Characterization of Thermally Reduced Graphene Oxide by Imaging Ellipsometry

Abstract

The dispersion functions for the refractive index and the extinction coefficient of single-and multiple-layer graphene oxide samples were measured by imaging spectroscopic ellipsometry in the wavelength range of 350-1000 nm and were compared to previously reported results measured by confocal microscopy. The dispersion functions for thin platelets were also compared to those obtained by standard spectroscopic ellipsometry on a deposit consisting of many overlapping graphene oxide layers. Changes were observed in both the thickness of the deposits and the values of the dispersion parameters following heating. A model is proposed to explain these observations, based on the removal of water between the graphene-oxide layers upon thermal treatment.

Making Graphene Luminescent by Oxygen Plasma Treatment

“…The spectrum of PLG yields the complex refractive index n= ϭ A n ϩ B n / 2 ϩ i*(A k ϩ B k / 2 ), with Cauchy parameters A n ϭ 2.76, A k ϭ 0.06, B n ϭ 3000, and B k ϭ 1500 (assuming graphene thickness of 0.34 nm), comparable to those obtained for GO. 32 The data presented so far are taken for single-layer graphene (SLG). A different behavior is observed for multilayer graphene (MLG), which remains nonluminescent following treatment.…”

Imaging ellipsometry of graphene

“…15 Graphene oxide layers have already been characterized by imaging ellipsometry. 16 In this letter, we demonstrate that imaging ellipsometric intensity ͑IEI͒ maps, imaging ellipsometry ͑IE͒, and imaging variable angle spectroscopic ellipsometry ͑IVASE͒ at visible light frequencies are powerful tools to detect and classify graphene flakes and to study their optical properties on a large variety of flat substrates. Due to the high lateral resolution of less than 1 m of our setup, the optical properties can be mapped over a graphitic flake.…”

Spectroscopic ellipsometry on Si/SiO2/graphene tri-layer system exposed to downstream hydrogen plasma: Effects of hydrogenation and chemical sputtering

“…Þ with typical values of C n ¼ 3000 and C k ¼ 1500 [30][31][32] were used for fitting, while d G and d die were fixed to 0.34 nm and 292 nm, respectively. The obtained optical contrast (Fig.…”

“…2(d)) very similar to values obtained in the literature. 13,[30][31][32][33][34] After graphene was chemically sputtered, light was still being absorbed at k Շ 500 nm that resulted in an optical contrast which could even be perceived by the naked eye or under optical microscope (Figs. 2(c) and 2(d)).…”