Berend Jonker1 Connie Li1 Kathleen McCreary1

1, Naval Research Laboratory, Washington, District of Columbia, United States

Single monolayer transition metal dichalcogenides (TMDs) exhibit exceptionally strong photoluminescence dominated by a combination of distinct neutral and charged exciton contributions. The dielectric screening is very low due to their two-dimensional character relative to bulk material, and their properties are thus strongly affected by their immediate environment. Because the exciton and trion binding energies are very large (~ 600 meV and ~30 meV, respectively), these characteristic emission features persist to room temperature. We show here that the surface charge associated with ferroelectric domains patterned into the lead zirconium titanate (PZT) film with a conductive atomic force microscope control the lateral spatial distribution of neutral and charged exciton populations in the adjacent WS2 monolayer [1]. This is manifested in the intensity and spectral composition of the photoluminescence measured in air at room temperature from the areas of WS2 over a ferroelectric domain with polarization dipole pointed either out of the surface plane or into the surface plane. Samples were fabricated by mechanically transferring large area monolayer WS2 grown by a CVD process onto a 100 nm thick (PZT) film on a conducting n-type strontium titanate wafer. The photoluminescence spectra from areas of the WS2 over up polarization domains in the PZT are dominated by neutral exciton emission, while those over down domains are dominated by trion emission, consistent with the corresponding charge produced by the domains at the WS2 / PZT interface. The hysteretic character of ferroelectric materials means that the TMD properties can be selectively reconfigured in a nonvolatile manner by changing the state of the ferroic substrate. This approach enables spatial modulation of TMD properties with a spatial resolution determined by the polarization domains in the underlying ferroelectric layer, with the potential for fabrication of lateral quantum dot arrays or p-n junctions in any geometry of choice.

[1] C.H. Li, K.M. McCreary and B.T. Jonker, ACS Omega 1, 1075 (2016).
This work was supported by core programs at NRL and the NRL Nanoscience Institute, and by the Air Force Office of Scientific Research #AOARD 14IOA018-134141.