Momentum-space indirect interlayer excitons in transition-metal dichalcogenide van der Waals heterostructures

Kunstmann, Jens; Mooshammer, Fabian; Nagler, Philipp; Chaves, Andrey; Stein, Frederick; Paradiso, Nicola; Plechinger, Gerd; Strunk, Christoph; Schüller, Christian; Seifert, Gotthard; Reichman, David R.; Korn, Tobias

doi:10.1038/s41567-018-0123-y

Cited by 279 publications

(396 citation statements)

References 38 publications

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“…Thus, electron–hole pairs that are optically generated in either of the constituent layers become spatially separated within a few tens of femtoseconds . These spatially separated charge carriers can form interlayer excitons (ILEs) on ultrafast timescales, which have been observed directly in photoluminescence (PL) for several TMDC heterobilayer combinations . Such ILEs have already been studied in conventional semiconductor heterostructures, e.g., coupled quantum wells.…”

Section: Introductionmentioning

confidence: 99%

“…There, different aspects such as exciton–exciton interaction and bosonic condensation of excitons were investigated, but only at low temperatures, limited by the weak ILE binding energies in these systems. ILEs in TMDC heterostructures are characterized by binding energies which significantly exceed those in GaAs heterostructures, making them stable beyond room temperature and robust against dissociation in applied electric fields. In addition, they have long radiative lifetimes, in stark contrast to intralayer excitons in TMDC monolayers, where subpicosecond radiative recombination can be observed .…”

Section: Introductionmentioning

confidence: 99%

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Interlayer Excitons in Transition‐Metal Dichalcogenide Heterobilayers

Nagler

Mooshammer

Kunstmann

et al. 2019

Physica Status Solidi (b)

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In heterobilayers consisting of different transition‐metal dichalcogenide (TMDC) monolayers, optically excited electron–hole pairs can be spatially separated into the adjacent layers due to a type‐II band alignment. However, they remain Coulomb correlated and form interlayer excitons (ILEs), which recombine radiatively. While these ILEs are observed in several TMDC material combinations, their characters and properties depend on the specific system. Herein, some of these peculiarities are demonstrated by comparing studies performed on two different heterobilayer combinations: MoS2–WSe2 and MoSe2–WSe2.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interlayer Excitons in Transition‐Metal Dichalcogenide Heterobilayers

Nagler

Mooshammer

Kunstmann

et al. 2019

Physica Status Solidi (b)

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“…This assembly can be used to create an almost unlimited number of combinations and extraordinary properties [1][2][3] for novel multifunctional electronic and optoelectronic devices. This assembly can be used to create an almost unlimited number of combinations and extraordinary properties [1][2][3] for novel multifunctional electronic and optoelectronic devices.…”

Section: Optical Memorymentioning

confidence: 99%

“…A charge trapping layer acting as a floating gate, instead of charge trapping at the materials/SiO 2 interface, can be introduced via gold nanoparticle/crosslinked poly(4-vinylphenol)/MoS 2 heterojunction-FETs, which significantly increase both the switching on/off ratio (≈10 6 ) and retention time (>10 4 s). This assembly can be used to create an almost unlimited number of combinations and extraordinary properties [1][2][3] for novel multifunctional electronic and optoelectronic devices. [30] Despite the long retention time and high on/off ratios of the recently developed vdWs heterostructure-based optical memory 2D van der Waals (vdWs) heterostructures exhibit intriguing optoelectronic properties in photodetectors, solar cells, and light-emitting diodes.…”

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confidence: 99%

Two‐Terminal Multibit Optical Memory via van der Waals Heterostructure

et al. 2018

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cells, [11] and memory. [12,13] Recently, vdWs heterostructure-based nonvolatile optical memory have been investigated for broad potential applications in imaging sensors, [14] logic gates, [15] optoelectronic demodulators, [16] and synaptic devices for neuromorphic systems. [17,18] These 2D vdWs materials and their hybrids are considered to be an ideal platform for nonvolatile optical memory owing to their strong light-matter interactions [19][20][21] and significant photogenerated charge trapping derived from their very large surface-to-volume ratio. [22][23][24] In addition, the mechanical strength and atomic thickness of 2D vdWs materials allow for device miniaturization in flexible and wearable optoelectronics. [25][26][27] The demonstration of 2D vdWs materials-based optical memory in the FETs of few-layer copper indium selenide (CuIn 7 Se 11 ) has been reported [14] along with hybrids of graphene/MoS 2[5] on a silicon substrate. These devices exhibit low optical switching on/off ratios (<1 [5] and ≈10 [14] ), high off-currents (≈400 µA [5] and 20 pA [14] ), and short retention times (50 s [14] ), preventing their use in high quality image sensors and multilevel storage devices.Using oxygen plasma treatments to create more charge trap sites at SiO 2 surface, monolayer MoS 2 -FET-based optical memory on silicon substrate has exhibited a long retention time of ≈10 4 s. [28] However, the data storage capacity of eight levels of the material remains limited for practical applications due to moderate switching on/off ratio of ≈4700. Importantly, the memory function of these devices relies on charge trapping of photoexcited carriers in defects and impurities on either the surface or material/SiO 2 interface. [5,28] This results in short retention times and sensitivity to environmental factors. A charge trapping layer acting as a floating gate, instead of charge trapping at the materials/SiO 2 interface, can be introduced via gold nanoparticle/crosslinked poly(4-vinylphenol)/MoS 2 heterojunction-FETs, which significantly increase both the switching on/off ratio (≈10 6 ) and retention time (>10 4 s). [29] Similarly, by storing charge in the hexagonal boron nitride (h-BN) dielectric layer, the WSe 2 /h-BN-FET-based optical memory on silicon also exhibited a high on/off ratio of 1.1 × 10 6 , realizing a data storage capability of up to 128 distinct states. [30] Despite the long retention time and high on/off ratios of the recently developed vdWs heterostructure-based optical memory 2D van der Waals (vdWs) heterostructures exhibit intriguing optoelectronic properties in photodetectors, solar cells, and light-emitting diodes. In addition, these materials have the potential to be further extended to optical memories with promising broadband applications for image sensing, logic gates, and synaptic devices for neuromorphic computing. In particular, high programming voltage, high off-power consumption, and circuital complexity in integration are primary concerns in the development of three-terminal optical memory devices....

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“…In addition to the well-documented low-dimensional nanostructures, for example, from 2D quantum wells or nanoflakes to 1D nanowires or quasi-1D nanotubes, and eventually to 0D nanoclusters or quantum dots, the discovery of single-layer graphene in 2004 has fundamentally changed the landscape of materials science, owing to its unique physical properties and stable single-atom or single-polyhedral thickness. [32,33] In experiment, measurements of the absorption and emission spectra, lattice vibrational modes, energy band structures, and photoconductivity of 2D vdW materials have been performed by using photoluminescence (PL) spectroscopy, [34,35] Raman spectroscopy, [36,37] angle-resolved photoemission spectroscopy, [38,39] optical pump-probe measurements, and optical pump-terahertz (THz) probe measurements. [32] To investigate such ultrafast dynamic processes of free charge carriers or quasiparticles and their interactions with lattice vibrations and unexcited cold electrons in 2D vdW materials, such as rapid exciton-exciton scattering, charge-transfer process, exciton-phonon interaction, and formation and recombination processes of excitons, tremendous efforts have been made from both theoretical and experimental aspects in recent years.…”

Section: Introductionmentioning

confidence: 99%

Time‐Resolved Terahertz Spectroscopy Studies on 2D Van der Waals Materials

Han

Wang

Zhang

2019

Advanced Optical Materials

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bulk diamond with tetrahedral structure, graphite is another allotrope of carbon with layered hexagonal lattice structure. In single-or few-layer graphite, which is also referred to as graphene, carbon atoms are strongly coupled by covalent bonds in plane and weakly coupled through van der Waals (vdW)-like interactions in layered direction; [2,3] such 2D-layered atomic crystals are commonly referred as "2D vdW materials." [3][4][5] Following the discovery of graphene, insulating 2D-layered hexagonal boron nitride (h-BN) was initially predicted in theory and then synthesized in experiments. [6,7] Soon after the discovery of semimetallic graphene and the insulating h-BN, semiconductinglayered 2D vdW materials, for example, transition-metal dichalcogenides (TMDs), monochalcogenides, black phosphorus (BP), 2D oxides, and transition meal carbides/carbon nitrides (MXenes) were synthesized by using different physical or chemical synthesis approaches such as mechanical exfoliations, wet-chemical synthesis, and chemical vapor-phase depositions. [4,5,[8][9][10][11][12][13][14] To date, more than 500 types of 2D vdW materials have been synthesized in laboratories.Owing to their high in-plane charge carrier mobility [15] and a wide range of energy bandgaps varies from tens of millielectron volts (meV) to few electron volts (eV), [16,17] semiconducting 2D materials have been viewed as a key component for the nextgeneration optoelectronic devices. [18][19][20][21][22] In addition to the high carrier mobility and wide spectral range, intriguing spin-valley physics, induced by the strong spin-orbit coupling and band structures, [23][24][25] strong Coulomb interactions, which originate from the strict out-of-plane quantum confinement and reduced dielectric screenings, [26,27] along with the large exciton-binding energies enrich the physical properties of photoexcited quasiparticles (e.g., exciton, trion, and biexciton) in 2D vdW semiconductors. In addition to these exciting physical properties, another attractive characteristic of 2D vdW materials is to stack them into structures that are constructed through vdW interactions, without introducing defects or lattice distortions at the interfaces. The unique physical properties along with the vdW interlayer interaction allow for the fabrication of highperformance devices with extremely fast responses, such as high-mobility GHz-frequency field-effect transistors, [28,29] fast response phototransistors, [30] and extremely sensitive chemical detectors. [31] Owing to the fascinating and technologically useful electronic and optical properties, 2D van der Waals (vdW) materials are viewed as the key component for the next-generation optoelectronic, photovoltaic, and nanoelectronic devices. Fully understanding the ultrafast carrier dynamics in 2D vdW materials is essential to study the fundamental physics and realize potential applications. Time-resolved terahertz (THz) spectroscopy is a powerful tool used to investigate the ultrafast carrier dynamics and transport properties in semiconduc...

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Momentum-space indirect interlayer excitons in transition-metal dichalcogenide van der Waals heterostructures

Cited by 279 publications

References 38 publications

Interlayer Excitons in Transition‐Metal Dichalcogenide Heterobilayers

Interlayer Excitons in Transition‐Metal Dichalcogenide Heterobilayers

Two‐Terminal Multibit Optical Memory via van der Waals Heterostructure

Time‐Resolved Terahertz Spectroscopy Studies on 2D Van der Waals Materials

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