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Density functional study of phonon-induced photocarrier capture in defective MoSe2

講師：Soungmin Bae (Korea Advanced Institute of Scence and Technology, KOREA)
日時：5月23日（木）13：30～
場所：工学研究院　総合研究棟　W202室
In recent years, optical electronic excitations and photocarrier dynamics in transition metal dichalcogenides (TMDCs) have been actively investigated in view of understanding photophysics in atomically thin materials and their optical device applications. According to recent studies on pristine TMDCs, acoustic phonons are involved in exciton generation and electron cooling processes [1,2]. In practical situations, TMDC samples usually contain a certain amount of defects and adsorbates, which act as ultrafast photocarrier trapping centers [3,4]. Meanwhile, although the exciton-phonon interaction in pristine TMDC is relatively well studied, defect-related photocarrier trappings remain vague. Here, we present our theoretical study of defect-induced photocarrier capture in MoSe2 by means of delta-self-consistent-field (ΔSCF) density functional theory calculations [5,6]. Starting from the ground-state MoSe2 with various defects, we explicitly minimize the geometry of its excited states at defects, thus explicitly treating the nonradiative decay through multi-phonon emission processes. Comparing our computational results with pump-probe measurement data, we conclude that the exciton trapping at a Se vacancy adsorbed by an oxygen molecule is a dominant photocarrier capture mechanism.

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