Characterizing the maximum number of layers in chemically exfoliated graphene

Abstract

An efficient route to synthesize macroscopic amounts of graphene is highly desired and bulk characterization of such samples, in terms of the number of layers, is equally important. We present a Raman spectroscopy-based method to determine the typical upper limit of the number of graphene layers in chemically exfoliated graphene. We utilize a controlled vapour-phase potassium intercalation technique and identify a lightly doped stage, where the Raman modes of undoped and doped few-layer graphene flakes coexist. The spectra can be unambiguously distinguished from alkali doped graphite, and modeling with the typical upper limit of the layers yields an upper limit of flake thickness of five layers with a significant single-layer graphene content. Complementary statistical AFM measurements on individual few-layer graphene flakes find a consistent distribution of the layer numbers.

Chemical and structural properties of reduced graphene oxide—dependence on the reducing agent

“…S5), crystallinity (Fig. S4, Table 3) [8][9][10][11][12][13][14][15][16][17][18][19]. The FWHM and intensity values of D and G mode indicate the distance between point-like defects smaller than 3 nm [19], for which phenomenological evaluation of distance between defects proposed by Concado et al [19] is not valid.…”

“…Description of structural and chemical properties of graphene materials basing on results obtained using X-ray photoelectron spectroscopy (XPS), X-ray excited Auger electron spectroscopy (XAES), reflection electron energy loss spectroscopy (REELS), Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), atomic force microscopy (AFM), etc., has been often reported [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The FTIR and XPS analyses are usually applied for probing the chemical properties of atoms, carbon hybridizations and oxygen groups, where FTIR analysis information is related to the bulk, and XPS information depth is limited to the surface, i.e.…”

“…few nanometers. By the recently developed complementary approaches of Raman spectroscopy [8][9][10][11][12][13][14][15][16][17][18][19] of few micrometers information depth, the surface AFM [8] and REELS [5] methods provide the information on the structural and chemical properties like level of disorder, dopants, the number of layers, the linear dispersion of electronic energy, the crystal orientation, the defects and strain [8][9][10][11][12][13][14][15][16][17][18][19].…”

Tuning Conductivity and Spin Dynamics in Few‐Layer Graphene via In Situ Potassium Exposure

“…[25][26][27] Chemical exfoliation was finalized using ultrasound tip sonication, as it is known to produce the best quality. [28,29] The properties of the starting material are well characterized by atomic force microscopy and Raman spectroscopy, which revealed that the restacked FLG is also present in the sample. [29] The dominant portion (90%) of the material consists of five layers or less, including monolayer content.…”

“…[28,29] The properties of the starting material are well characterized by atomic force microscopy and Raman spectroscopy, which revealed that the restacked FLG is also present in the sample. [29] The dominant portion (90%) of the material consists of five layers or less, including monolayer content. Prior to in situ measurements, the undoped FLG was heated to 400 C for 30 min in high vacuum (2 Â 10 À6 mbar) to remove any residual solvents.…”