  Monolithic realization of metallic 1T and semiconducting 2H polymorphic
phases makes MoS2 a potential candidate for future microelectronic circuits.
Though co-existence of these phases has been reported, a method for engineering
a stable 1T phase in a scalable manner, compatible with the standard device
fabrication schemes is yet to emerge. In addition, there are no comprehensive
studies on the electrical properties of the 1T phase. In this manuscript, we
demonstrate a controllable and scalable 2H to 1T phase engineering technique
for MoS2 using Ar + H2 microwave plasma. The technique enables us to realize 1T
MoS2 starting from the 2H phase of arbitrary thickness and area. Our method
allows lithographically defining continuous 1T regions in a 2H sample. The 1T
samples withstand aging in excess of a few weeks in ambience and show a thermal
stability up to 300 C, making it suitable for standard device fabrication
techniques. We conduct both two-probe and four-probe electrical transport
measurements on devices with back-gated field effect transistor geometry in a
temperature range of 4 K to 300 K. The 1T samples exhibit Ohmic current-voltage
characteristics in all temperature ranges without any dependence to the gate
voltage, a signature indicative of metallic state. The sheet resistance of our
1T MoS2 sample is considerably lower than that of 2H samples while the carrier
concentration of the 1T sample is few orders of magnitude higher than that of
the 2H samples. In addition, our samples show negligible temperature dependence
of resistance from 4 K to 300 K ruling out any hoping mediated or activated
electrical transport.
