An Insight into the Phase Transformation of WS<sub>2</sub> upon Fluorination.

Radhakrishnan, Sruthi; Das, Deya; Deng, Liangzi; Sudeep, Parambath M; Colas, Guillaume; de Los Reyes, Carlos A; Yazdi, Sadegh; Chu, Ching Wu et al. · Adv Mater · 2018

basic_science · Level V

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Abstract

The transformation from semiconducting to metallic phase, accompanied by a structural transition in 2D transition metal dichalcogenides has attracted the attention of the researchers worldwide. The unconventional structural transformation of fluorinated WS<sub>2</sub> (FWS<sub>2</sub> ) into the 1T phase is described. The energy difference between the two phases debugs this transition, as fluorination enhances the stability of 1T FWS<sub>2</sub> and makes it energetically favorable at higher F concentration. Investigation of the electronic and optical nature of FWS<sub>2</sub> is supplemented by possible band structures and bandgap calculations. Magnetic centers in the 1T phase appear in FWS<sub>2</sub> possibly due to the introduction of defect sites. A direct consequence of the phase transition and associated increase in interlayer spacing is a change in friction behavior. Friction force microscopy is used to determine this effect of functionalization accompanied phase transformation.