Thermal enhancement of chemical doping in graphene: a Raman spectroscopy study

Abstract

The Raman spectrum of monolayer graphene deposited on the top of a silicon oxide/silicon substrate was investigated as a function of temperature up to 515 K. An anomalous temperature dependence of the Raman features was observed, including an important frequency upshift for the Raman G band at room temperature, after the heating process. On the other hand, the frequency of the Raman G(') band is only slightly affected by the thermal treatment. We discuss our experimental results in terms of doping and strain effects associated with the interaction of graphene with the substrate and with the presence of water in the sample. We conclude that the doping effect gives the most important contribution to the spectral changes observed after the thermal cycle.

Temperature and face dependent copper–graphene interactions

“…The values of A(2D) at high temperatures differ for each copper substrate, suggesting that different levels of doping are reached by each sample. It should be noted that in a similar experiment performed on CVD graphene [20] or exfoliated graphene [32,33] on SiO 2 /Si substrates, the observed 2D band intensity decrease was also observed. Nevertheless, the doping levels reached are still inferior to those observed for CVD graphene on copper substrates.…”

Raman spectra of bilayer graphene covered with Poly(methyl methacrylate) thin film

“…The data in brackets are standard errors of the mean for corresponding data in Figure 3. This result markedly differs from that of uncovered graphene, 21 for which the two 2D peaks soften with increase in temperature (i.e., laser power). 21 In the current study, the laser wavelength and slit were 633 nm and 1800 mm -1 , respectively.…”

“…This result markedly differs from that of uncovered graphene, 21 for which the two 2D peaks soften with increase in temperature (i.e., laser power). 21 In the current study, the laser wavelength and slit were 633 nm and 1800 mm -1 , respectively. The stiffness of graphene can be ascribed to compression strain induced by the laser.…”

“…For bare graphene, the 2D band softens with increase in temperature (i.e., laser power). 21 Graphene and few-layer graphene (FLG) were prepared by Graphene Industries using micromechanical cleavage and were independently characterized via optical microscopy and Raman spectroscopy. The monolayer was examined based on its single peak characteristics and the full width at half-maximum (FWHM) of the 2D peak.…”

“…This finding is in agreement with previous results. 17,21 It should be noted that the power was too low to make sure enough strong signal in Fig. 4(b).…”