We fabricated a van der Waals heterostructure of WS 2 –ReSe 2 and studied its charge-transfer properties. Monolayers of WS 2 and ReSe 2 were obtained by mechanical exfoliation and chemical vapor deposition, respectively. The heterostructure sample was fabricated by transferring the WS 2 monolayer on top of ReSe 2 by a dry transfer process. Photoluminescence quenching was observed in the heterostructure, indicating efficient interlayer charge transfer. Transient absorption measurements show that holes can efficiently transfer from WS 2 to ReSe 2 on an ultrafast timescale. Meanwhile, electron transfer from ReSe 2 to WS 2 was also observed. The charge-transfer properties show that monolayers of ReSe 2 and WS 2 form a type-II band alignment, instead of type-I as predicted by theory. The type-II alignment is further confirmed by the observation of extended photocarrier lifetimes in the heterostructure. These results provide useful information for developing van der Waals heterostructure involving ReSe 2 for novel electronic and optoelectronic applications and introduce ReSe 2 to the family of two-dimensional materials to construct van der Waals heterostructures.
Efficient hole transfer from monolayer WS 2 to ultrathin amorphous black phosphorus
The newly developed van der Waals materials allow fabrication of multilayer heterostructures. Early efforts have mostly focused on heterostructures formed by similar materials. More recently, however, attempts have been made to expand the types of materials, such as topological insulators and organic semiconductors. Here we introduce an amorphous semiconductor to the material library for constructing van der Waals heterostructures. Samples composed of 2 nm amorphous black phosphorus synthesized by pulsed laser deposition and monolayer WS 2 obtained by mechanical exfoliation were fabricated by dry transfer. Photoluminescence measurements revealed that photocarriers excited in WS 2 of the heterostructure transfer to amorphous black phosphorus, in the form of either energy or charge transfer, on a time scale shorter than the exciton lifetime in WS 2 . Transient absorption measurements further indicate that holes can efficiently transfer from WS 2 to amorphous black phosphorus. However, interlayer electron transfer in either direction was found to be absent. The lack of electron transfer from amorphous black phosphorus to WS 2 is attributed to the localized electronic states in the amorphous semiconductor. Furthermore, we show that a hexagonal BN bilayer can effectively change the hole transfer process.
- Award ID(s):
- 1505852
- Publication Date:
- NSF-PAR ID:
- 10104418
- Journal Name:
- Nanoscale Horizons
- Volume:
- 4
- Issue:
- 1
- Page Range or eLocation-ID:
- 236 to 242
- ISSN:
- 2055-6756
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Publisher's Version of Record
- https://doi.org/10.1039/C8NH00234G
