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X-ORIGINAL-URL:https://lpcno.insa-toulouse.fr/
BEGIN:VEVENT
UID:MEC-5eac43aceba42c8757b54003a58277b5@lpcno.insa-toulouse.fr
DTSTART:20231214T140000Z
DTEND:20231214T160000Z
DTSTAMP:20231129T145400Z
CREATED:20231129
LAST-MODIFIED:20240110
SUMMARY:Séminaire de George Kioseoglou
DESCRIPTION:Department of Materials Science and Technology, University of Crete, Greece\nInstitute of Electronic Structure and Lasers – FORTH\nTuning the optoelectronic properties of TMD monolayers\nwith dielectric environment, photochemical processes, and strain\n \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[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\n
X-ALT-DESC;FMTTYPE=text/html:<p data-index="0"><span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;Institut de Chimie Radicalaire, Marseille&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}"><span class="VIiyi"><span class="JLqJ4b ChMk0b" data-language-for-alternatives="en" data-language-to-translate-into="fr" data-phrase-index="0"><span class="JLqJ4b ChMk0b" data-language-for-alternatives="en" data-language-to-translate-into="fr" data-phrase-index="0"><span class="JLqJ4b ChMk0b" data-language-for-alternatives="en" data-language-to-translate-into="fr" data-phrase-index="0"><span class="JLqJ4b ChMk0b" data-language-for-alternatives="en" data-language-to-translate-into="fr" data-phrase-index="0"><span class="mec-address">Department of Materials Science and Technology, University of Crete, Greece<br />
Institute of Electronic Structure and Lasers &#8211; FORTH</span></span></span></span></span></span></span></p>
<h3 data-index="0"><span class="VIiyi"><span class="JLqJ4b ChMk0b" data-language-for-alternatives="en" data-language-to-translate-into="fr" data-phrase-index="0">Tuning the optoelectronic properties of TMD monolayers<br />
with dielectric environment, photochemical processes, and strain</span></span></h3>
<p>&nbsp;</p>
<p>Monolayers of MX2-type (M=Mo or W and X=S or Se) Transition Metal Dichalcogenides (TMDs),<br />
exhibit promising potential for future 2D nanoelectronics owing to their unique optoelectronic properties.<br />
In this seminar, I will present methods for controlling their optical and electronic characteristics through<br />
the engineering of their dielectric environment, employing photochemical methods, and applying<br />
mechanical strain.<br />
In particular, we investigate WS2 monolayers on pre-patterned Si/SiO2 substrates with cylindrical<br />
wells of 3 μm in diameter, analyzing strained and suspended areas. Raman mapping experiments quantify<br />
strain, revealing a 10-fold enhanced photoluminescence efficiency with strong neutral excitonic emission<br />
in suspended areas. TMD optoelectronic properties are chemically controlled by modulating the Fermi level<br />
using UV-assisted photochlorination processes in WS2 [1,2] and WSe2 [3] monolayers. Systematic shifts<br />
and relative intensities between neutral and charged excitons indicate a controllable decrease in electron<br />
density, switching WSe2 from n-type to p-type semiconductor. Validation of chlorine species and DFT<br />
calculations [4] predict p-type doping through chlorine adsorption on selenium vacancy sites. Investigating<br />
isotropic, biaxial strain at room temperature on WS2 monolayers shows a strong shift on the order of ~130<br />
meV per % of strain in neutral exciton emission and a decrease in circular polarization degree [5]. The<br />
analysis reveals the interplay of energy and polarization relaxation channels, as well as variations in the<br />
exciton oscillator strength affecting long-range exchange interactions.</p>
<p>[1] I. Demeridou, et al. 2D Mater. 6, 015003 (2018)<br />
[2] I. Demeridou, et al. Appl. Phys. Lett. 118, 123103 (2021)<br />
[3] E. Katsipoulaki, et al., 2D Mater. 10, 045008 (2023)<br />
[4] G. Vailakis, et al. Phys. Rev. Mater 7, 024004 (2023)<br />
[5] G. Kourmoulakis, et al., Appl. Phys. Lett. 123, (2023) in print</p>

URL:https://lpcno.insa-toulouse.fr/events/seminaire-de-george-kioseoglou/
ORGANIZER;CN=:MAILTO:
CATEGORIES:Séminaires
LOCATION:Bât. 27, Salle 2.20 (2ème étage gauche), INSA, 135 av. de Rangueil, Toulouse
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