Metallization of molybdenum diselenide under nonhydrostatic compression

It is known that metallization can greatly facilitate chemical reactions and dramatically change electric transport properties of materials. The search for materials displaying metallization at low pressure is one of the most urgent challenges. In this paper, pressure-induced metallization of molybdenum diselenide (MoSe2) under nonhydrostatic compression has been studied experimentally using Hall effect and X-ray diffraction measurements combined with diamond anvil cell techniques. In situ conductivity and Hall effect measurements under pressure reveal a monotonic decrease of resistivity mostly related to a significant increase of the carrier density by a factor of 4. Above 35.7 GPa, the sample acquires a metallic character with a characteristic increase of the mobility from 9.9 to 16.2 cm2 V-1 s-1 and saturation of the carrier concentration at 5.1 × 1020 cm-3. These results show that the metallization of powder MoSe2 can be initiated by a reduced pressure of 35.7 GPa under nonhydrostatic compression, compared to that above 40 GPa with a single-crystal sample under hydrostatic compression [Nat. Commun. 2015, 6, 7312]. The mechanisms of anisotropic-stress-induced metallization for such reduced initiation pressure have been discussed.