Spatially Resolved Persistent Photoconductivity in MoS2–WS2 Lateral Heterostructures
| Autor: | Jeffrey L. Blackburn, Benjamin M. Kupp, Prasana Sahoo, Dmitri V. Voronine, Sanjini U. Nanayakkara, Thomas M. Wallis, Hanyu Zhang, Elisa M. Miller, Pavel Kabos, Samuel Berweger |
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| Rok vydání: | 2020 |
| Předmět: |
Photoluminescence
Materials science Photoconductivity Exciton General Engineering General Physics and Astronomy Heterojunction 02 engineering and technology Photon energy 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Molecular physics 0104 chemical sciences Condensed Matter::Materials Science Dark state Excited state General Materials Science 0210 nano-technology Absorption (electromagnetic radiation) |
| Zdroj: | ACS Nano. 14:14080-14090 |
| ISSN: | 1936-086X 1936-0851 |
| Popis: | The optical and electronic properties of 2D semiconductors are intrinsically linked via the strong interactions between optically excited bound species and free carriers. Here we use near-field scanning microwave microscopy (SMM) to image spatial variations in photoconductivity in MoS2-WS2 lateral multijunction heterostructures using photon energy-resolved narrowband illumination. We find that the onset of photoconductivity in individual domains corresponds to the optical absorption onset, confirming that the tightly bound excitons in transition metal dichalcogenides can nonetheless dissociate into free carriers. These photogenerated carriers are most likely n-type and are seen to persist for up to days. Informed by finite element modeling we reveal that they can increase the carrier density by up to 200 times. This persistent photoconductivity appears to be dominated by contributions from the multilayer MoS2 domains, and we attribute the flake-wide response in part to charge transfer across the heterointerface. Spatial correlation of our SMM imaging with photoluminescence (PL) mapping confirms the strong link between PL peak emission photon energy, PL intensity, and the local accumulated charge. This work reveals the spatially and temporally complex optoelectronic response of these systems and cautions that properties measured during or after illumination may not reflect the true dark state of these materials but rather a metastable charged state. |
| Databáze: | OpenAIRE |
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