Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor

Das, Anindya; Pisana, Simone; Chakraborty, Biswanath; Piscanec, S.; Saha, Sounik; Waghmare, Umesh V.; Новоселов, К. С.; Krishnamurthy, H. R.; Geǐm, A. K.; Ferrari, Andrea C.; Sood, A. K.

doi:10.1038/nnano.2008.67

Cited by 3,305 publications

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“…Pos(2D) ∼ 2686 cm −1 , and the 2D to G intensity and area ratios, I(2D)/I(G) and A(2D)/A(G), are 3.1 and 8.8, respectively. This indicates p-doping <100 meV, 47 confirming the electrical characterization. Further, while pristine SLG absorbs 2.3% of the incident light, 67 doping can significantly decrease the absorption by Pauli blocking.…”

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confidence: 67%

Photothermoelectric and Photoelectric Contributions to Light Detection in Metal–Graphene–Metal Photodetectors

et al. 2014

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Graphene's high mobility and Fermi velocity, combined with its constant light absorption in the visible to far-infrared range, make it an ideal material to fabricate high-speed and ultrabroadband photodetectors. However, the precise mechanism of photodetection is still debated. Here, we report wavelength and polarization-dependent measurements of metal−graphene−metal photodetectors. This allows us to quantify and control the relative contributions of both photothermo-and photoelectric effects, both adding to the overall photoresponse. This paves the way for a more efficient photodetector design for ultrafast operating speeds.KEYWORDS: Graphene, photodetectors, Raman spectroscopy, photoresponse, optoelectronics T he unique optical and electronic properties of graphene make it ideal for photonics and optoelectronics. 1 A variety of prototype devices have already been demonstrated, such as transparent electrodes in displays 2 and photovoltaic modules, 3 optical modulators, 4 plasmonic devices, 4−9 microcavities, 10,11 and ultrafast lasers. 12 Among these, a significant effort is being devoted to photodetectors (PDs). 6,10,11,13−25 Various photodetection schemes and architectures have been proposed to date. The simplest configuration is the metal− graphene−metal (MGM) PD, in which graphene is contacted with metal electrodes as the source and drain. 13−18 These PDs can be combined with metal nanostructures enabling local surface plasmons and increased absorption, realizing an enhancement in responsivity (i.e., the ratio of the lightgenerated electrical current to the incident light power). 6,26 Microcavity based PDs were also used, with increased light absorption at the cavity resonance frequency, again achieving an increase in responsivity. 10,11 Another scheme is the integration of graphene with a waveguide to increase the effective interaction length with light. 25,27 Hybrid approaches employ semiconducting nanodots as light-absorbing media. 22 In this case, light excites electron−hole (e−h) pairs in the nanodots; the electrons are trapped in the nanodot, while the holes are transferred to graphene, thus effectively gating it. 22 Under applied drain−source bias, this results in a shift in the Dirac point, thus a modulation of the drain−source current. 22 Due to the long trapping time of the electrons within the dot, the transferred holes can cycle many times through the phototransistor before relaxation and e−h recombination. This gives a photoconductive gain; i.e., one absorbed photon effectively results in an electrical current of several electrons. Responsivities >10 7 A/W were reported, 22 but with a millisecond time scale, not suitable for, e.g., high-speed optical communications. Devices were also fabricated for detection of THz light. 28,29 In this low energy range, Pauli blocking forbids the direct excitation of e−h pairs due to finite doping. Instead, an antenna coupled to source and gate of the device excites plasma waves within the channel. These are rectified, leading to a detectable dc out...

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confidence: 67%

Photothermoelectric and Photoelectric Contributions to Light Detection in Metal–Graphene–Metal Photodetectors

et al. 2014

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“…15 The ratio of the integrated intensity of the 2D mode compared to that of the G mode, I 2D /I G , is presented in the spatial map of Fig 3c. On the suspended portion of the sample, the 2D-mode intensity is enhanced, while the G-mode strength is not strongly affected. Consistent with studies of top-gated graphene FETs, 15 as well as with recent theoretical results suggesting a reduced intensity of the doubly resonant features in doped graphene from enhanced electron-electron scattering, 36 this ratio provides a criterion to distinguish neutral and doped graphene. We note that the absolute intensities for G-and 2D-modes measured in the free-standing and supported regions might differ simply because of an optical etalon effect associated with the different dielectric environments.…”

mentioning

confidence: 99%

“…[13][14][15][16] Our experiment did not permit us to calibrate the Raman measurements with a systematic variation of doping, since no gate was present in our sample geometry.…”

mentioning

confidence: 99%

Probing the Intrinsic Properties of Exfoliated Graphene: Raman Spectroscopy of Free-Standing Monolayers

Berciaud¹,

Ryu²,

Brus³

et al. 2009

Nano Lett.

526

489

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The properties of pristine, free-standing graphene monolayers prepared by mechanical exfoliation of graphite are investigated. The graphene monolayers, suspended over open trenches, are examined by means of spatially resolved Raman spectroscopy of the G-, D-, and 2D-phonon modes. The G-mode phonons exhibit reduced energies (1580 cm -1 ) and increased widths (14 cm -1 ) compared to the response of graphene monolayers supported on the SiO 2 -covered substrate. From analysis of the G-mode Raman spectra, we deduce that the free-standing graphene monolayers are essentially undoped, with an upper bound of 2×10 11 cm -2 for the residual carrier concentration. On the supported regions, significantly higher and spatially inhomogeneous doping is observed. The free-standing graphene monolayers show little local disorder, based on the very weak Raman D-mode response. The two-phonon 2D mode of the free-standing graphene monolayers is downshifted in frequency compared to that of the supported region of the samples and exhibits a narrowed, positively skewed line shape.

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“…and A(2D)/A(G) are 2.53 and 6.3 respectively, indicating doping∼9·10 12 cm −2 (∼290meV) [55,56,59]. We also get I(D)/I(G)∼0.14, indicating that the fabrication process does introduce significant defects in the SLG electrode [57,60].…”

Section: Introductionmentioning

confidence: 63%

“…Pos(G) is 1587.5cm −1 with FWHM(G)∼19.6cm −1 . The 2D to G peak intensity and area ratios, I(2D)/I(G) and A(2D)/A(G), are 4.32 and 7.16 respectively, suggesting a p-doping∼2.4·10 12 cm −2 (∼200meV) [55,56,59]. Fig.4a (blue curve) plots the SLG Raman spectrum after device fabrication and point-to-point subtraction of the Si reference using the same procedure.…”

Section: Introductionmentioning

confidence: 98%

Vertically Illuminated, Resonant Cavity Enhanced, Graphene–Silicon Schottky Photodetectors

et al. 2017

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We report vertically-illuminated, resonant cavity enhanced, graphene-Si Schottky photodetectors (PDs) operating at 1550nm. These exploit internal photoemission at the graphene-Si interface. To obtain spectral selectivity and enhance responsivity, the PDs are integrated with an optical cavity, resulting in multiple reflections at resonance, and enhanced absorption in graphene. Our devices have wavelength-dependent photoresponse with external (internal) responsivity∼20mA/W (0.25A/W). The spectral-selectivity may be further tuned by varying the cavity resonant wavelength. Our devices pave the way for developing high responsivity hybrid graphene-Si free-space illuminated PDs for free-space optical communications, coherence optical tomography and light-radars.

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Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor

Cited by 3,305 publications

References 31 publications

Photothermoelectric and Photoelectric Contributions to Light Detection in Metal–Graphene–Metal Photodetectors

Photothermoelectric and Photoelectric Contributions to Light Detection in Metal–Graphene–Metal Photodetectors

Probing the Intrinsic Properties of Exfoliated Graphene: Raman Spectroscopy of Free-Standing Monolayers

Vertically Illuminated, Resonant Cavity Enhanced, Graphene–Silicon Schottky Photodetectors

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