Metal‐Contact‐Induced Transition of Electrical Transport in Monolayer MoS2: From Thermally Activated to Variable‐Range Hopping

An understanding of the charge transport of atomically thin molybdenum sulfide (MoS2) beneath the metal electrode is important to the fabrication of high performance MoS2 devices and circuits with low ohmic contact resistance. However, the carrier‐transport mechanism in monolayer MoS2 under the metal contact has remained elusive due to the difficulty of measuring the electrical properties of MoS2 in contact regions. A method to distinguish the electrical properties of monolayer MoS2 in the contact and channel regions is presented. Temperature‐dependent measurement reveals that the carriers are thermally activated in the channel region. In contrast, they are variable‐range hopping in the contact region. This difference can be attributed to the localization of the MoS2 electronic states caused by metal‐induced gap states. The variable‐range hopping transport in MoS2 under contact causes a reduction of the carrier mobility and an increase in the contact resistance. This work is not only important for fundamental understanding of metal–MoS2 contact but also helpful for further improving the performance of MoS2 devices. A method to distinguish the electrical properties of monolayer MoS2 in channel and contact regions is presented. Temperature‐dependent measurement reveals that the carriers are thermally activated in the channel region. In contrast, they are variable‐range hopping in the contact region. This difference can be attributed to the localization of the MoS2 electronic states caused by metal‐induced gap states.