Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS 2 Field Effect

Following the discovery of graphene, [1, 2, 3] two-dimensional (2D) materials have emerged as one of the most important research topics in condensed matter physics because of promising applications of these materials. [4, 5, 6] In particular, semiconducting layered materials, [7, 8] such as transition metal dichalcogenides (TMD), [9, 10] can complement graphene because of their intrinsic bandgaps. [11, 12] In particular, molybdenum disulfide (MoS2) is a layered semiconducting TMD and therefore exhibits a bandgap, [13, 14] and strong mechanical properties. [15] Moreover, unique physical properties, including spin-valley coupling and the layer dependence of the band structure in MoS2, have been demonstrated.