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Origin of Hybrid 1T- and 2H-WS 2 Ultrathin Layers by Pulsed Laser Deposition

2015; American Chemical Society; Volume: 119; Issue: 49 Linguagem: Inglês

10.1021/acs.jpcc.5b09277

1932-7455

Tamie A. J. Loh, Daniel H. C. Chua,

MXene and MAX Phase Materials

Partial 2H-to-1T phase transition in two-dimensional (2D) WS2 grown by pulsed laser deposition is discovered through X-ray photoelectron spectroscopy. The resulting hybrid structure is observed only on substrates of the noble metals Ag and Au, whereas other metals such as Ni and Al produced only 2H-WS2. The origin of the 1T-phase is attributed to electron doping of the WS2 lattice by Ag or Au atoms, in a mechanism reminiscent of Li in the intercalation of WS2 and the related MoS2 structure. The doping process is viable as both Ag and Au atoms are able to donate one electron each, leading to the formation of a stable d10 shell and a phase transformation in the WS2 structure from 2H-to-1T. In the case of Ni, however, the formation of nickel oxides at the metal surface inhibits its ability to donate electrons to the WS2 lattice, whereas Al is unable to act as electron donor for WS2. Thus, the 1T-phase is absent in either of these substrates.