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O: Fachverband Oberflächenphysik
O 88: 2D Materials: Stacking and Heterostructures (joint session O/HL)
O 88.4: Vortrag
Donnerstag, 20. März 2025, 15:45–16:00, H6
SNOM of lateral TMDC heterojunctions — •Philipp Schwendke1, Samuel Palato1, and Julia Stähler1,2 — 1Humboldt-Universität zu Berlin — 2Fritz-Haber-Institut der MPG
Two transition metal dichalcogenide monolayers, joined together laterally, form a one-dimensional heterojunction where charge transfer with associated space charge region and current rectification have been shown experimentally [1]. Furthermore, there are unique local electronic properties determining the excitonic response in the boundary region. Nanoscale spectroscopic methods are needed for the observation of such local optical properties. We use scanning near-field optical microscopy (SNOM) in combination with a continuous wave (cw) light source at 633 nm, as well as a pulsed laser tunable in a wide range from 250 nm to 1300 nm. We employ pseudo-heterodyne modulation for noise suppression and optical phase information, and quadrature-assisted discrete demodulation in order to use the tunable light source at kHz repetition rates. Resonant SNOM measurements show a quenching near the WS2-MoS2 boundary, which can be indicative of local energy shifts or electronic states specific to the boundary region. This is complementary to previous measurements which show quenching of photoluminescence [2], attributing it to exciton recombination. In addition, the agreement of results acquired with cw and pulsed light sources paves the way towards time-resolved near-field measurements.
[1] Li et al., Science, vol 349, p 524 (2015)
[2] Chou et al., Nanoscale, vol 14, p 6323 (2022)
Keywords: SNOM; lateral heterojunction; TMDC