Regensburg 2025 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 53: 2D Semiconductors and van der Waals Heterostructures V
HL 53.8: Vortrag
Donnerstag, 20. März 2025, 17:00–17:15, H15
Engineering carrier density and exciton polarization in WSe2 monolayers via photochlorination — •Eirini Katsipoulaki1,2, George Vailakis1,3, Delphine Lagarde4, Vishwas Jindal4, Konstantinos Mourtzidis4, Xavier Marie4, Ioannis Paradisanos1, George Kopidakis1,3, George Kioseoglou1,3, and Emmanouel Stratakis1,2 — 1FORTH/IESL, Heraklion, Greece — 2Dpt. of Physics, UoC, Heraklion, Greece — 3Dpt. of Materials Science and Engineering, UoC, Heraklion, Greece — 4Universite de Toulouze, INSA-CNRS-UPS, LPCNO, Toulouze, France
Transition Metal Dichalcogenides (TMDs) represent a special class of 2D van der Waals materials. Unlike their 3D-counterparts, which are indirect gap semiconductors, the monolayers exhibit a direct bandgap, leading to a significant enhancement in photoluminescence quantum yield. TMDs feature valley dependent optical selection rules, establishing them as promising candidates for atomically thin optoelectronic devices. A key factor influencing the performance of TMDs in these applications is the carrier density. To address this, we demonstrate the modulation of the Fermi level in WSe2 monolayers using an UV-assisted photochlorination method. Systematic shifts and relative intensities between charged and neutral excitons indicate a controllable decrease of the electron density and switch WSe2 from n- to a p-type semiconductor. DFT calculations predict Cl2 adsorption at Se vacancies. Furthermore, this method can strongly impact the circular polarization degree of excitons. These findings indicate that photochlorination can tailor nanopatterned lateral p-n junctions.
Keywords: Transition Metal Dichalcogenides; WSe2; photochlorination; excitons; p-type semiconductor