[12a-W521-1~10] 17.3 Layered materials

▲ [12a-W521-9] Stability of monolayer WSe₂ and MoS₂ in an aqueous solution under light irradiation

〇(D)Wenjin Zhang¹, Kazunari Matsuda¹, Yuhei Miyauchi¹ (1.Inst. of Advanced Energy, Kyoto Univ.)

Keywords:transition metal dichalcogenides

Atomically thin transition metal dichalcogenides (TMDCs) MX₂, where M and X are a transition metal and a chalcogen, respectively, have become attractive candidate for future electronics and optoelectronics applications such as gas/bio sensors and photocatalyst because of their unique optical and electrical properties[1-4]. Due to their extremely large specific surface area, their physical or chemical performances and stabilities are easily affected by the surface electrochemical interactions between TMDCs and their environment[5]. Thus, it is important to clarify the impact of surface interactions on the stability of TMDCs for their real applications.
Here we report the stability of monolayer (1L) WSe₂ and MoS₂ under light irradiation in aqueous solutions with various pH. We probed degradation of the sample as a function of time using photoluminescence (PL) spectroscopy. PL properties in air and aqueous solutions were compared for 1L-WSe₂ and 1L-MoS₂.
Figure 1 shows the PL intensity change of 1L-WSe₂ and 1L-MoS₂ in distilled water (pH = 7) under visible light irradiation (580 nm, 800 W/cm²). The PL intensities of 1L-WSe₂ show remarkable decrease whereas 1L-MoS₂ were stable. These results suggest that only 1L-WSe₂ was degraded. These differences are mainly attributed to the different surface reactions between 1L-TMDCs and O₂/H₂O redox couple; the difference is induced by the alignments of band levels of 1L-WSe₂(MoS₂) and O₂/H₂O redox potentials and photo-generated holes.