Temperature and Gate Voltage Dependent Raman Spectra of Single-Layer Graphene

Abstract

Raman spectra of electrostatically gated single-layer graphene are measured from room temperature to 560 K to sort out doping and thermally induced effects. Repeated heating cycles under Ar led to convergent first-order temperature coefficients of the G-band (χ(G) = -0.03 cm(-1)/K) and the 2D-band (χ(2D) = -0.05 cm(-1)/K) frequencies, which are independent of doping level as long as the Fermi level does not shift with temperature. While the intrinsic behavior may be different (e.g., χ(G) ∼ -0.02 cm(-1)/K near room temperature), these values appear more appropriate in describing responses of most graphene samples on SiO(2) substrates. The more negative χ(G) value than theoretical expectations may be explained by interactions with the substrate reducing the lattice thermal expansion contribution to the temperature dependence of G-band frequency. Enhanced interactions with the substrate may also be responsible for zero-charge, room-temperature G-band line width increase and 2D-band frequency downshift.

Thermal and optical properties of freestanding flat and stacked single-layer graphene in aqueous media

“…The Raman 2D peak downshift with temperature at a rate of À0.067 cm À1 /K is shown in the inset of Figure 3(a). This result is close to the reported value for monolayer graphene suspended above porous membrane, 18 but higher than the values obtained from supported graphene, 15,19 probably due to the elimination of substrate interaction. The temperature dependence of freestanding graphene ribbon on excitation laser powers is then acquired.…”

“…Raman spectroscopy was also applied to extract the local temperature of freestanding stacked graphene since Raman 2D-mode of flat single-layer graphene shows a temperature dependence as reported in previous literature. 15 In our experiment, a stacked graphene ribbon was placed in a microscopy cryostat (Janis), and a 785 nm diffraction-limited laser spot (<500 nm) was then fixed on the stacked region that displayed the highest thermal emission intensity. When the temperature of the whole sample was increased by a heating stage in the microscope chamber, the Raman 2D-mode of stacked graphene showed a linear downshift with the temperature-scaling coefficient of À0.066 cm À1 K À1 (Fig.…”

Ferroelectrically driven spatial carrier density modulation in graphene

“…Shifts in the Raman G-band mode frequency [24][25][26] provide a spatially resolved probe of the carrier density in graphene without the need for device fabrication, which could screen or alter the nature of the interactions 27,28 (Fig. 1b).…”

Nanoscale optical thermometry using a time-correlated single-photon counting in an illumination-collection mode

“…Moreover, probe fabrication remains complicated. Several non-contact methods, such as infrared thermometry, 6 Raman scattering spectroscopy, 7 and fluorescence thermometry, 8,9 have been reported. For example, temperature imaging of a carbon nanotube network transistor has been performed by infrared thermometry, 6 and Nguyen et al examined the temperature and gate voltage-dependent Raman spectra of single-layer graphene.…”

“…For example, temperature imaging of a carbon nanotube network transistor has been performed by infrared thermometry, 6 and Nguyen et al examined the temperature and gate voltage-dependent Raman spectra of single-layer graphene. 7 Fluorescence thermometry techniques have been widely used for biological subjects. 8,9 Kucsco et al measured the temperature of biological samples (human embryonic fibroblast WS1 cells) with high temperature resolution using nanodiamonds on the basis of their nitrogen-vacancy color centers.…”