Anomalous Room-Temperature Photoluminescence from Nanostrained MoSe2 Monolayers

Strain-engineering is an effective strategy for manipulating the optical properties of low-dimensional materials. The integration of two-dimensional (2D) transition metal dichalcogenides (TMDs) with other low-dimensional materials can yield nonplanar assemblies that manifest a diverse range of interfaces and strain characteristics. Here we identify anomalous photoluminescence from nonplanar assemblies of 2D MoSe2 monolayers with silicon nanowires (SiNWs). Near-field scanning optical microscopy identifies pronounced photoluminescence (PL) at 1.38 eV that emanates from the nonplanar region between the 2D monolayer and SiNW. Notably, this anomalous emission is distinct (by nearly 200 meV) from the characteristic A exciton emission of monolayer MoSe2. Scanning transmission electron microscopy reveals an apparent straining of the MoSe2 unit cell across a 3-5 nm wide linear region coincident with the nonplanar boundary. The unusual room-temperature PL may be ascribed to a new excitonic state localized within this nanostrained region of the 2D MoSe2 monolayer. This work highlights the importance of nanoscale manipulation of strain in low-dimensional materials to elicit desired control over excitonic and other properties.