Abstract
Time-resolved terahertz (THz) spectroscopy is a powerful technique for the determination of charge transport properties in photoexcited semiconductors. However, the relatively long wavelengths of THz radiation and the diffraction limit imposed by optical imaging systems reduce the applicability of THz spectroscopy to large samples with dimensions in the millimeter to centimeter range. Exploiting THz near-field spectroscopy, we present the first time-resolved THz measurements on a single exfoliated 2D nanolayered crystal of a transition metal dichalcogenide (WS2). The high spatial resolution of THz near-field spectroscopy enables mapping of the sheet conductance for an increasing number of atomic layers. The single-crystalline structure of the nanolayered crystal allows for the direct observation of low-energy phonon modes, which are present in all thicknesses, coupling with free carriers. Density functional theory calculations show that the phonon mode corresponds to the breathing mode between atomic layers in the weakly bonded van der Waals layers, which can be strongly influenced by substrate-induced strain. The non-invasive and high-resolution mapping technique of carrier dynamics in nanolayered crystals by time-resolved THz time domain spectroscopy enables possibilities for the investigation of the relation between phonons and charge transport in nanoscale semiconductors for applications in two-dimensional nanodevices.
| Original language | English |
|---|---|
| Pages (from-to) | 15557-15562 |
| Number of pages | 6 |
| Journal | ACS Applied Nano Materials |
| Volume | 5 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - 28 Oct 2022 |
Funding
The authors thank Mohamed Abdelkhalik for performing the AFM measurements. S.T.H. and J.G.R. acknowledge the support from Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) (Vici 680-47-628), A.R.C. acknowledges the support from the ITN 4PHOTON Marie Sklodowska Curie grant agreement no. 721394, S.E. acknowledges the support from the NWO START-UP grant (740.018.009), and M.E.F. acknowledges the support for the theoretical methodology coherently connecting the optical excitation to phonons from the Center for Molecular Quantum Transduction (CMQT), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0021314 for funding.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| European Union's Horizon 2020 - Research and Innovation Framework Programme | 721394 |
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek | 740.018.009, 680-47-628 |
Keywords
- density functional theory
- electron-phonon coupling
- terahertz conductivity
- terahertz near-field spectroscopy
- transition metal dichalcogenide
- tungsten disulfide
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Researchers from Eindhoven University of Technology Detail Findings in Nanodevices (High-frequency Sheet Conductance of Nanolayered Ws2 Crystals for Two-dimensional Nanodevices)
Curto, A. G., ter Huurne, S. & Godiksen, R. H.
23/11/22
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