(562e) Nanoantennae-Induced Hot Carriers and Nonlinear Susceptibility in 2D Materials

Monolayer (1L) two-dimensional nanocrystals (NC) offer a direct bandgap spanning the solar spectrum as well as enhanced electron mobility and gate tunability. Decoration of 1LNC by nanoantennae (NAE) such as noble metal nanoparticles has enhanced measured photocurrent. But challenges in simulating, characterizing and fabricating 1LNC-NAE hybrid structures has constrained their implementation in functional optoelectronic devices like photovoltaics.

This work examined examined nonlinear susceptibility in 1L transition metal dichalcogenide (TMD) and NAE-modulated injection of hot eletrons into 1LNC, i.e., graphene and TMD. The work evaluated and compared 1LNC that had been chemical vapor deposited or liquid exfoliated from bulk material. 1LNC were decorated by gold (Au), silver (Ag) and platinum (Pt) NAE through three methods (i) evaporation, (ii) drop-casting and (iii) direct reduction.

Electron energy loss spectroscopy (EELS) was used to predict and induce plasmon bright, dark, and hybrid modes. EELS enabled quantitative femtosecond-scale measurement of spectroscopic plasmon dephasing and nanometer-resolved mapping of electric fields on the 1LNC-NAE hybrids. Coupled and discrete dipole simulations were used to characterize radiative and intraband dephasing in order to distinguish contributions to photocurrent from field enhanced electron hole pair generation and carrier injection.

Hyper Rayleigh Scattering (HRS) was used to measure nonlinear susceptibility in comparison with indirect classical calculations. Data from these measurements represent the first reported use of HRS to characterize nonlinear optical properties of liquid exfoliated 1LTMD. Measured values agreed with a priori estimates using density function theory to within 21%. This represented a circa ten-fold improvement compared with previous microscopy-based measurements.

Comparison of simulation, optoelectronic characterization and fabrication of 1LNC-NAE hybrids show new ways to integrate enhanced 1LNC into devices.