Abstract
We present in situ high-pressure synchrotron X-ray diffraction (XRD) and Raman spectroscopy study, and electrical transport measurement of single crystal WSe2 in diamond anvil cells with pressures up to 54.0–62.8 GPa. The XRD and Raman results show that the phase undergoes a pressure-induced iso-structural transition via layer sliding, beginning at 28.5 GPa and not being completed up to around 60 GPa. The Raman data also reveals a dominant role of the in-plane strain over the out-of plane compression in helping achieve the transition. Consistently, the electrical transport experiments down to 1.8 K reveals a pressure-induced metallization for WSe2 through a broad pressure range of 28.2–61.7 GPa, where a mixed semiconducting and metallic feature is observed due to the coexisting low- and high-pressure structures.
Highlights
We present in situ high-pressure synchrotron X-ray diffraction (XRD) and Raman spectroscopy study, and electrical transport measurement of single crystal WSe2 in diamond anvil cells with pressures up to 54.0–62.8 GPa
The crystal structure was characterized by single crystalline XRD (Fig. 1(b)), which shows a (00l) preferable orientation
At 1.8 GPa, the XRD profile is well reproduced by the 2Hc structure (see the bottom of Fig. 1(c))
Summary
We present in situ high-pressure synchrotron X-ray diffraction (XRD) and Raman spectroscopy study, and electrical transport measurement of single crystal WSe2 in diamond anvil cells with pressures up to 54.0–62.8 GPa. The electrical transport experiments down to 1.8 K reveals a pressure-induced metallization for WSe2 through a broad pressure range of 28.2–61.7 GPa, where a mixed semiconducting and metallic feature is observed due to the coexisting low- and high-pressure structures. MoS2 was reported to undergo a pressure-induced semiconductor to metal transition at high pressure[15,16]. The pressure-induced metallization in MoS2 was related to a 2Hc to 2Ha iso-structural transition via layer sliding[15,16,18]. A first-principles study revealed an anomaly at 40 GPa consistently in the bulk modulus, Young’s modulus and Poisson’s ratio of WSe2, which may imply a possible structural transition[21,24]. More experimental efforts are necessary to gain comprehensive knowledge of the high-pressure behavior of WSe2
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