Open AccessUltrafast Pump–Probe Microscopy on 2D Transition Metal Dichalcogenides
Author(s) -
Boandoh Stephen,
Hsiao Fu-He,
Shin Bongki,
Mack Majvor,
Grote Linus P.,
Wang Rongbin,
Han Yimo,
Lou Jun,
Koch Norbert,
Nickel Norbert H.,
Luo Chih-Wei,
Tsai Yu-Tsung
Publication year - 2022
Publication title -
advanced photonics research
Language(s) - English
Resource type - Journals
ISSN - 2699-9293
DOI - 10.1002/adpr.202200046
Subject(s) - charge carrier , tungsten disulfide , molybdenum disulfide , monolayer , heterojunction , materials science , ultrashort pulse , transition metal , molecular physics , condensed matter physics , nanotechnology , optoelectronics , physics , chemistry , optics , laser , biochemistry , metallurgy , catalysis
Although microscopic techniques have been used to characterize transition metal dichalcogenides (TMDs), direct observation of charge carrier dynamics distribution in TMDs with diverse shapes remains unexplored. Herein, ultrafast pump–probe microscopy (UPPM) is employed to reveal the carrier dynamics distribution in molybdenum disulfide (MoS 2 ) and tungsten disulfide (WS 2 ) monolayer of four shapes: triangular (t‐MoS 2 ), curved triangular (c‐MoS 2 ), triangular (t‐WS 2 ), and hexagonal (h‐WS 2 ). Monitoring the photon transmission T at 1.55 eV after pumping with a photon energy of 3.1 eV, a negative Δ T / T occurs in t‐MoS 2 and c‐MoS 2 , while a positive Δ T / T is detected in t‐WS 2 and h‐WS 2 after 3–7 ps time evolution. This distinctive behavior is attributed to deep/shallow defects below the conduction band minimum (CBM) in MoS 2 and WS 2 . Spatial‐independent Δ T / T is observed in t‐MoS 2 and t‐WS 2 , while the Δ T / T in c‐MoS 2 has a rapid decay of photoexcited carriers at the vertices and curved edges. Additionally, a threefold symmetry of Δ T / T is revealed in h‐WS 2 , attributed to the dissimilar occupation of defect states near the h‐WS 2 CBM. This work paves the way for examining charge carrier dynamics of various shapes of TMDs and provides a unique microscopic method for studying the charge carrier dynamics in emerging TMDs heterostructures.