Charge transfer across monolayer/bilayer MoS2 lateral interface and its influence on exciton and trion characteristics

Abstract

The charge transfer phenomenon is identified to be a major factor determining exciton and trion characteristics of atomically thin MoS2 layers in various stacking configurations. We report photoluminescence (PL) from CVD-grown layered MoS2 in the presence of a skewed or a deformed triangular-shaped monolayer/bilayer (1L/2L) lateral interface. Integrated PL mapping images over the 1L and 2L MoS2 regions revealed that the neutral exciton emission was significantly enhanced and exhibited an oscillatory behavior in its intensity in the 1L region near the 1L/2L boundary, whereas the negative trion emission remained unchanged. The interplays among the number of MoS2 layers, a substrate, and a geometric boundary structure of the 1L/2L lateral interface turned out to be important in charge transfer due to a modulation in work functions. Density functional theory predicted that the work functions of 1L and 2L MoS2 were strongly influenced not only by the substrate material but also by the edge configuration of MoS2. As a result, PL intensity profiles showed rich features such as a stacking dependent decomposition of excitons and trions, a sharp spectroscopic contrast along the 1L/2L boundary, and a charge transfer relevant to the work function difference at the lateral interface. Our results demonstrate that understanding the MoS2 PL is useful in characterizing the electronic properties in 2D layered nanostructures and sheds light on possible new device applications.