Conductivity mapping of graphene on polymeric films by terahertz time-domain spectroscopy

Whelan, Patrick Rebsdorf; Huang, Deping; Mackenzie, David; Messina, Sara; Li, Zhancheng; Li, Xin; Li, Yunqing; Booth, Tim; Jepsen, Peter Uhd; Shi, Haofei; Bøggild, Peter

doi:10.1364/oe.26.017748

Cited by 34 publications

(55 citation statements)

References 24 publications

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“…[28,29] Graphene on SiO 2 was fabricated from CVD growth of graphene on Cu(111) foils [30] prepared by contact-free annealing [31] and subsequent bubbling transfer [32]. Electrical parameters σ DC , n and µ of graphene in all these substrates measured in this [22] and regions of high mobility of charge carriers in graphene supported on PEN [29] (despite our measurements are undertaken in larger spatial regions and under ambient conditions).…”

Section: Graphene Growth Transfer To Flexible Substrates and Graphenmentioning

confidence: 99%

“…where n B = n sub -1 and δ= ωd sub /c with substrate thickness d. [22] By fitting σ s ω to the Drude…”

Section: Thz-tds Measurements Of Graphene On Arbitrary Substratesmentioning

confidence: 99%

“…We point out that that this consistency test is desirable when using thin (~100 µm) polymeric films. The timing between internal reflections in these substrates (~1-2 ps) is commonly shorter than the width of the time-domain waveforms in the commercial setup (see figure 2(a)), and the frequency-dependent sheet conductivity σ s (ω) must be calculated by using a complicated fitting expression accounting for internally reflected transients [22] since THz transients from direct transmission and internal reflections are overlapping, and thus occurring within the same waveform. In contrast, σ s (ω) can be extracted using a simpler formalism in the broadband setup, covering only a directly transmitted transient since the width of the time-domain waveforms in this setup is shorter than the intervals between internal reflections as shown in figure 2(a).…”

Section: Thz-tds Of Graphene Films On Arbitrary Thin Substratesmentioning

confidence: 99%

“…With these values (σ DC , τ), we can then proceed to calculate n, µ and ν F * of graphene on PEN, PET and substrates [15][16][17]22,33]. The median values of n and µ from the THz-TDS measurements and the corresponding n H and µ H from Hall measurements are also highlighted in the figure (see also Table 1), and show a reasonable quantitative agreement for both substrates (detailed analysis in the next subsection).…”

Section: Extracted Electronic (ν F * ) and Electrical (N µ) Parametementioning

confidence: 99%

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Fermi velocity renormalization in graphene probed by terahertz time-domain spectroscopy

Whelan¹,

Shen²,

Zhou³

et al. 2020

2D Mater.

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We demonstrate terahertz time-domain spectroscopy (THz-TDS) to be an accurate, rapid and scalable method to probe the interaction-induced Fermi velocity renormalization ν F * of charge carriers in graphene. This allows the quantitative extraction of all electrical parameters (DC conductivity σ DC , carrier density n, and carrier mobility µ) of large-scale graphene films placed on arbitrary substrates via THz-TDS. Particularly relevant are substrates with low relative permittivity (< 5) such as polymeric films, where notable renormalization effects are observed even at relatively large carrier densities (> 10 12 cm -2 , Fermi level > 0.1 eV). From an application point of view, the ability to rapidly and non-destructively quantify and map the electrical (σ DC , n, µ) and electronic (ν F * ) properties of large-scale graphene on genericsubstrates is key to utilize this material in applications such as metrology, flexible electronics as well as to monitor graphene transfers using polymers as handling layers.

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Section: Graphene Growth Transfer To Flexible Substrates and Graphenmentioning

confidence: 99%

“…where n B = n sub -1 and δ= ωd sub /c with substrate thickness d. [22] By fitting σ s ω to the Drude…”

Section: Thz-tds Measurements Of Graphene On Arbitrary Substratesmentioning

confidence: 99%

Section: Thz-tds Of Graphene Films On Arbitrary Thin Substratesmentioning

confidence: 99%

Section: Extracted Electronic (ν F * ) and Electrical (N µ) Parametementioning

confidence: 99%

See 2 more Smart Citations

Fermi velocity renormalization in graphene probed by terahertz time-domain spectroscopy

Whelan¹,

Shen²,

Zhou³

et al. 2020

2D Mater.

Self Cite

View full text Add to dashboard Cite

show abstract

“…[197] Skalsky et al [198] used few-layer graphene prepared by liquid phase exfoliation from graphite mixed in various concentrations with teflon pellets and characterized the composite by THz spectroscopy. [197] Skalsky et al [198] used few-layer graphene prepared by liquid phase exfoliation from graphite mixed in various concentrations with teflon pellets and characterized the composite by THz spectroscopy.…”

Section: Thz Properties Of Graphenementioning

confidence: 99%

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Kužel

Němec

2019

Advanced Optical Materials

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Transport of charges is a fundamental process in many high-tech applications including photovoltaic or optoelectronic devices, but also in more ordinary components such as unsophisticated wires and other circuitry. The development of nanotechnologies resulted in the fabrication of highly complex materials consisting of a large variety of nanosized elements, which inevitably involve a multitude of charge transport processes occurring on various time-and length-scales. Figure 1 summarizes the most common nanoelements with high application potential.For example, the electrodes employed in Grätzel solar cells [1] are composed of percolated networks of a huge number of metal oxide nanoparticles (top-left panel in Figure 1). Colloidal nanocrystals form the basis for thin film electronics and flexible electronic devices. [2] The synthetic approaches control their composition, size and electronic structure (energy levels, density of states within the bands and in the bandgap) and the charge-carrier transport. [2,3] Nanowires and nanotubes made of conventional semiconductors are quasi 1D systems combining Terahertz spectroscopy has been used for almost two decades for investigations of nanomaterials, including nanocrystals, nanoparticles, nanowires, nanotubes or 2D crystals. Its great importance stems from the fact that it is a noncontact method and, owing to its high frequency and broadband character, it is capable of characterizing charge transport properties within individual nano-objects but also among them. In addition, probing of photoinitiated ultrafast charge dynamics is possible thanks to the sub-picosecond time resolution. Despite this unprecedented potential, the interpretation of the measured terahertz conductivity spectra in many materials is still intensively debated. Herein is presented a review of the experiments performed on nanostructures of conventional semiconductors and on carbon nanomaterials (graphene and carbon nanotubes) during the past decade. The state of the art of the theoretical formalism is provided and discussed, including the intrinsic response, as well as the role of inherent heterogeneity and of the experimental conditions.

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Microscale Spectroscopic Mapping of 2D Optical Materials

Dong

Yetisen

Köhler

et al. 2019

Advanced Optical Materials

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be used for flexible touch screens and displays, printable electronics, and thinfilm photovoltaics, [4] while FETs made of graphene can be used for highly sensitive biosensors. [5] Another 2D material MoS 2 , a direct-bandgap semiconductor, has applications in ultrasensitive photodetectors, transistors, and gas-sensing devices. [6][7][8][9] Other 2D materials have also shown potential in photovoltaic devices, memory, and light-emitting diodes (LEDs). [10,11] Broad application potential of 2D materials in optoelectronic devices, photonic devices, and optical sensors is mainly based on their unique optical performances. [12] 2D materials can be fabricated based on their layered structure. In the molecular structures of these materials, the atoms are bonded hard in the same plane, but the bond effect between two lateral layers is weak due to van der Waals forces. [13] 2D materials can be roughly categorized as semimetal like graphene, semiconductor like transition metal dichalcogenides (TMDs), and insulator like hexagonal boron nitride (hBN) from the aspect of bandgap differences. [14] Due to the experimentally practical manipulation of monolayer and multilayer 2D materials, remarkable optical performances can be realized for a wide range of optical applications. For example, the number of layers of 2D materials can strongly influence the photoluminescence performance. [15] The unconventional optical performances including adsorption and emission, light sensitivity, as well as plasmonic effects of 2D materials are closely related to their inner physical properties such as carrier mobility, density of states, and band structure based on the interaction of atoms, structural symmetry, and stacking patterns. [16,17] Through the control of layer number which could influence the bandgap value, 2D materials could react to different spectrum ranging from ultraviolet to infrared light. [18] Doping strategies are also effective to modify intrinsic 2D semiconductors and improve the response with respect to an extended range of spectrum. [19,20] The assessment of the optical properties of 2D materials is indispensable for device and sensor development. [21] Based on detailed surface mapping and spectral information, the suitability of 2D materials for optical devices or sensor applications can be thoroughly studied. [22,23] Microscopy, direct 2D mapping of materials, can provide basic spatial information, [24] while spectroscopy can offer one more dimensional spectral information which is 2D materials have unique optical properties due to their ultrathin layered structures, and are emerging as promising materials for optoelectronic devices. To characterize and evaluate these properties, diffraction-limited spectroscopic mapping, also known as microscale spectroscopic imaging, has been developed to provide abundant spatial and spectral information. The usefulness of microscale spectroscopic mapping for unique property study of 2D optical materials is addressed. Advances in both mature and growing microscale spectroscopic mapping...

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Conductivity mapping of graphene on polymeric films by terahertz time-domain spectroscopy

Cited by 34 publications

References 24 publications

Fermi velocity renormalization in graphene probed by terahertz time-domain spectroscopy

Fermi velocity renormalization in graphene probed by terahertz time-domain spectroscopy

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Microscale Spectroscopic Mapping of 2D Optical Materials

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