Terahertz Conductivity of Semiconducting 2H and Metallic 1T Phases of Molybdenum Disulfide.

Molybdenum disulfide (MoS) has been extensively studied in its commonly occurring semiconducting 2H phase. Recent synthetic advances have enabled the bulk synthesis of the catalytically promising metallic 1T phase. However, the conductivity of bulk 1T-MoS has not been well characterized to ascertain the carrier transport properties. Terahertz (THz) spectroscopy is an ideal technique for obtaining this crucial information because it is a noncontact method of measuring the conductivity of emerging materials with ultrafast time resolution. This work applies THz spectroscopy to bulk 2H-MoS and 1T-MoS, representing the first application of the technique on the 1T phase, with measurements confirming the semiconducting character of 2H-MoS and the metallic character of 1T-MoS. This study provides new insight into the metallic nature of bulk 1T-MoS and a direct comparison to the semiconducting 2H phase that, together with physical characterization to obtain material parameters, are important for optimizing applications in catalysis devices and beyond.