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Abstract The electronic properties of 2D materials play a critical role in determining their potential for device applications. Despite rapid developments in 2D semiconductors, studies of fundamental electronic parameters, including the electronic gap and ionization energy, are limited, with significant discrepancies in reported values. The study focuses on tungsten disulfide (WS₂) and investigates the electronic structure of films comprising an increasing number of layers deposited with two different methods: direct synthesis via metal–organic chemical vapor deposition (MOCVD) and additive mechanical transfer of exfoliated single layers. The films are characterized via Raman, UV–vis, and photoluminescence spectroscopies, as well as ultraviolet photoelectron and inverse photoemission spectroscopies (UPS/IPES). The electronic gap of WS₂ is found to decrease from 2.43 eV for the monolayer to 1.97 eV for the trilayer, indicating a bulk transition at the trilayer thickness. This reduction in the electronic gap is primarily due to the downward shift of the conduction band minimum relative to the valence band maximum. A comparative analysis with MOCVD‐grown WS₂ reveals a slightly larger electronic gap for MOCVD‐grown samples, attributed to differences in defect densities. The electronic levels evaluated through UPS/IPES highlight the significant influence of preparation methods on the electronic properties of WS₂. 

Transition metal dichalcogenide heterostructures show strong interactions and can imprint a moiré potential to a separate layer. 

Transition metal dichalcogenides (TMDs) have attracted much interest in recent years due to their emerging material properties. In monolayer TMDs, such as MoS2, extreme quantum confinement is achieved in the monolayer limit. Although monolayer TMDs represent an ideal platform to explore excitonic physics using ultrafast spectroscopy, this exploration is currently limited by confusion regarding the origin of certain spectral features, including the below-bandgap PIA feature observed in pump-probe experiments. In this work, we document an absence of PIA features immediately after photoexcitation, indicating a lack of strong optically-induced biexciton formation. Below-bandgap PIA features are observed to grow in with a time constant of 110 ± 10 fs, indicative of other factors responsible for their origin. These results indicate that optically-induced biexciton formation is most likely not responsible for the previously observed PIA features in MoS2 monolayers.