Electronic Structure and Luminescence of Quasi-Freestanding MoS<sub>2</sub> Nanopatches on Au(111)

Krane, Nils; Lotze, Christian; Läger, Julia M.; Reecht, Gaël; Franke, Katharina J.

doi:10.1021/acs.nanolett.6b02101

Cited by 69 publications

(71 citation statements)

References 29 publications

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“…The renormalization of the bandgap in 2D materials due to the substrate is an intriguing concept that receives a lot of attentions recently1017343839. It has been shown that single-layer MoS 2 grown on Au(111) has a significantly lower bandgap than that grown on graphite103839.…”

Section: Resultsmentioning

confidence: 99%

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Bandgap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures

et al. 2016

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The van der Waals interaction in vertical heterostructures made of two-dimensional (2D) materials relaxes the requirement of lattice matching, therefore enabling great design flexibility to tailor novel 2D electronic systems. Here we report the successful growth of MoSe2 on single-layer hexagonal boron nitride (hBN) on the Ru(0001) substrate using molecular beam epitaxy. Using scanning tunnelling microscopy and spectroscopy, we found that the quasi-particle bandgap of MoSe2 on hBN/Ru is about 0.25 eV smaller than those on graphene or graphite substrates. We attribute this result to the strong interaction between hBN/Ru, which causes residual metallic screening from the substrate. In addition, the electronic structure and the work function of MoSe2 are modulated electrostatically with an amplitude of ∼0.13 eV. Most interestingly, this electrostatic modulation is spatially in phase with the Moiré pattern of hBN on Ru(0001) whose surface also exhibits a work function modulation of the same amplitude.

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Section: Resultsmentioning

confidence: 99%

“…It has been shown that single-layer MoS 2 grown on Au(111) has a significantly lower bandgap than that grown on graphite103839. In the case of MoSe 2 , earlier study suggested that MoSe 2 on graphite has a smaller gap than MoSe 2 on bilayer graphene17.…”

Section: Resultsmentioning

confidence: 99%

Bandgap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures

et al. 2016

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“…The electroluminescence has been observed in two-dimensional monolayer field-effect transistors or p-n light-emitting diodes made of MoS 2 [9,10], WSe 2 [11], and WS 2 [12]. Single layer molybdenum disulfide (MoS 2 ) field-effect transistors can emit electroluminescence (visible light) at 1.8 eV thanks to its direct band gap [9].…”

Section: Light-emitting Diodesmentioning

confidence: 99%

“…Single layer molybdenum disulfide (MoS 2 ) field-effect transistors can emit electroluminescence (visible light) at 1.8 eV thanks to its direct band gap [9]. Electrostatic gating must be used to improve control and efficiency of light emission.…”

Section: Light-emitting Diodesmentioning

confidence: 99%

Graphene against Other Two-Dimensional Materials: A Comparative Study on the Basis of Photonic Applications

Vargas-Bernal¹

2017

Graphene Materials - Advanced Applications

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Two-dimensional materials represent the basis of technological development to produce applications with high added value for nanoelectronics, photonics, and optoelectronics. In first decades of this century, these materials are impelling this development through materials based on carbon, silicon, germanium, tin, phosphorus, arsenic, antimony, and boron. 2D materials for photonic applications used until now are graphene, silicene, germanene, stanene, phosphorene, arsenene, antimonene, and borophene. In this work, the main strategies to modify optical properties of 2D materials are studied for achieving photodetection, transportation, and emitting of light. Optical properties analyzed here are refractive index, extinction coefficient, relative permittivity, absorption coefficient, chromatic dispersion, group index, and transmittance. The transmittance spectra of various two-dimensional materials are presented here with the aim of classifying them from photonic point-of-view. A performance comparison between graphene and other twodimensional materials is done to help the designer choose the best design material for photonic applications. In next three decades, a lot of scientific research will be realized to completely exploit the use of 2D materials either as single monolayers or as stacked multilayers in several fields of knowledge with a special emphasis in the optoelectronics and photonic industry in benefit of the industry and ultimately to our society.

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“…We show that the spatial intensity variations can be simulated by including vibration-assisted tunneling in addition to the Franck-Condon picture.Scanning tunneling microscopy (STM) experiments were performed at a temperature of 4.6 K in ultra-high vacuum. Monolayer-islands of MoS 2 were grown on a clean Au(111) surface by depositing Mo in an H 2 S atmosphere (5 · 10 −5 mbar) and annealing to 800 K [30,31].2,5-Bis(3-dodecylthiophen-2-yl)thieno[3,2b]thiophene (BTTT) [phthalocyanine (H 2 Pc)] molecules were evaporated at 365 K [680 K] onto the surface held at 200 K [120 K]. Differential-conductance (dI/dV ) spectra and maps were recorded using lock-in detection with 921 Hz modulation frequency.Deposition of BTTT molecules on MoS 2 leads to partially ordered structures with the molecules lying parallel to each other (Figure 1a) [33].…”

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confidence: 99%

Vibrational Excitation Mechanism in Tunneling Spectroscopy beyond the Franck-Condon Model

et al. 2020

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Vibronic spectra of molecules are typically described within the Franck-Condon model. Here, we show that highly resolved vibronic spectra of large organic molecules on a single layer of MoS2 on Au(111) show spatial variations in their intensities, which cannot be captured within this picture. We explain that vibrationally mediated perturbations of the molecular wave functions need to be included into the Franck-Condon model. Our simple model calculations reproduce the experimental spectra at arbitrary position of the STM tip over the molecule in great detail.Vibronic excitations are resonant transitions from a molecular ground state to an electronically and vibrationally excited state. These excitations are typically described by the Franck-Condon model. The essence of it are fast electronic transitions treated in Born-Oppenheimer approximation, such that the excitations occur without changes in the nuclear coordinates or momentum. Vibronic excitations in single molecules on surfaces can be detected as resonant sidebands of positive or negative ion resonances in tunneling spectroscopy [1][2][3][4][5][6][7] with apparent submolecular variations due to distinct close-lying orbitals [8][9][10]. In contrast to these resonant excitations, inelastic vibrational excitations far below resonance [6,12,13] are described by a change in the nuclear coordinates, which leads to a modified tunneling matrix element and to the opening of a new tunneling path [7,15,16]. Hence, off-resonant inelastic tunneling and resonant vibronic transitions are treated in distinct and complementary models [17]. The combination of both models would be akin to phonon-mediated electronic transitions in crystal structures [18,19], where the activation of a phonon mode enables otherwise forbidden electronic transitions, as the initial and final state have different parallel momentum in the electronic band structure [20][21][22][23]. Signatures of such combined excitations in single molecules have not been reported to date.Recent tunneling experiments have revealed some limitations of the Franck-Condon model. In cases, where the electronic energy level spacing was similar to vibrational energies, it was found that avoided level crossings determine the resonant sidebands [24,25]. In other cases, intensity variations of the resonant sidebands along an organic molecule were interpreted in terms of coherent vibrational modes with different symmetries [8] or with vibration-assisted coupling of wave functions of different symmetry in molecule and tip [26]. Selection rules could not be derived, because the vibrational modes and associated nuclear displacements of the molecule could not be identified owing to an insufficient experimental energy resolution probably limited by non-adiabatic relaxation effects.Here, we show that vibration-assisted tunneling and Franck-Condon excitations are crucial for a complete vibronic model. To benchmark our model we use vibronic spectra of large organic molecules on a single layer of MoS 2 on Au(111). The van-der-Waals lay...

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Electronic Structure and Luminescence of Quasi-Freestanding MoS₂ Nanopatches on Au(111)

Cited by 69 publications

References 29 publications

Bandgap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures

Bandgap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures

Graphene against Other Two-Dimensional Materials: A Comparative Study on the Basis of Photonic Applications

Vibrational Excitation Mechanism in Tunneling Spectroscopy beyond the Franck-Condon Model

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Electronic Structure and Luminescence of Quasi-Freestanding MoS2 Nanopatches on Au(111)

Cited by 69 publications

References 29 publications

Bandgap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures

Bandgap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures

Graphene against Other Two-Dimensional Materials: A Comparative Study on the Basis of Photonic Applications

Vibrational Excitation Mechanism in Tunneling Spectroscopy beyond the Franck-Condon Model

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Electronic Structure and Luminescence of Quasi-Freestanding MoS₂ Nanopatches on Au(111)