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DTSTART;TZID=Europe/Paris:20231214T150000
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DTSTAMP:20260418T133227
CREATED:20231209T063906Z
LAST-MODIFIED:20231211T083020Z
UID:9430-1702566000-1702573200@fermi.univ-tlse3.fr
SUMMARY:Tuning the optoelectronic properties of TMD monolayers with dielectric environment\, photochemical processes\, and strain. - (George Kioseoglou / LPCNO / Seminar). - 14/12/2023\, 15H
DESCRIPTION:George Kioseoglou\, University of Crete\, Greece \nSéminaire LPCNO\, seminar room\, INSA\, Build. 27\, Room 2.20 (2nd floor left) \nSummary :\nMonolayers of MX2-type (M=Mo or W and X=S or Se) Transition Metal Dichalcogenides (TMDs)\,\nexhibit promising potential for future 2D nanoelectronics owing to their unique optoelectronic properties.\nIn this seminar\, I will present methods for controlling their optical and electronic characteristics through\nthe engineering of their dielectric environment\, employing photochemical methods\, and applying\nmechanical strain.\nIn particular\, we investigate WS2 monolayers on pre-patterned Si/SiO2 substrates with cylindrical\nwells of 3 μm in diameter\, analyzing strained and suspended areas. Raman mapping experiments quantify\nstrain\, revealing a 10-fold enhanced photoluminescence efficiency with strong neutral excitonic emission\nin suspended areas. TMD optoelectronic properties are chemically controlled by modulating the Fermi level\nusing UV-assisted photochlorination processes in WS2 [1\,2] and WSe2 [3] monolayers. Systematic shifts\nand relative intensities between neutral and charged excitons indicate a controllable decrease in electron\ndensity\, switching WSe2 from n-type to p-type semiconductor. Validation of chlorine species and DFT\ncalculations [4] predict p-type doping through chlorine adsorption on selenium vacancy sites. Investigating\nisotropic\, biaxial strain at room temperature on WS2 monolayers shows a strong shift on the order of ~130\nmeV per % of strain in neutral exciton emission and a decrease in circular polarization degree [5]. The\nanalysis reveals the interplay of energy and polarization relaxation channels\, as well as variations in the\nexciton oscillator strength affecting long-range exchange interactions. \n\n[1] I. Demeridou\, et al. 2D Mater. 6\, 015003 (2018)\n[2] I. Demeridou\, et al. Appl. Phys. Lett. 118\, 123103 (2021)\n[3] E. Katsipoulaki\, et al.\, 2D Mater. 10\, 045008 (2023)\n[4] G. Vailakis\, et al. Phys. Rev. Mater 7\, 024004 (2023)\n[5] G. Kourmoulakis\, et al.\, Appl. Phys. Lett. 123\, (2023) in print
URL:https://fermi.univ-tlse3.fr/event/tuning-the-optoelectronic-properties-of-tmd-monolayers-with-dielectric-environment-photochemical-processes-and-strain-george-kioseoglou-lpcno-seminar-14-12-2023-15h/
LOCATION:Salle 220\, LPCNO\, INSA – LPCNO : 135 avenue de Rangueil\, toulouse\, 31077\, France
CATEGORIES:Events,LPCNO,Seminars
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