Reproducible Ultrahigh Electromagnetic SERS Enhancement in Nanosphere-Plane Junctions

TL;DR

This paper demonstrates highly reproducible and intense electromagnetic SERS enhancement in nanosphere-plane junctions, revealing nonlinear effects at low laser powers, advancing single-molecule detection capabilities.

Contribution

It reports reproducible ultrahigh electromagnetic SERS enhancement factors up to 10^9, achieved in a controlled nanosphere-plane junction system, with insights into power-dependent nonlinear effects.

Findings

Achieved SERS enhancement factors up to 10^9 with low error

Demonstrated reproducibility in SERS enhancement in nanosphere-plane junctions

Discovered nonlinear SERS effects at low laser powers

Abstract

Surface enhanced Raman scattering (SERS) in nanoscale hotspots has been placed great hopes upon for identification of minimum chemical traces and in-situ investigation of single molecule structures and dynamics. However, previous work consists of either irreproducible enhancement factors (EF) from random aggregates, or moderate EFs despite better reproducibility. Consequently, systematic study of SERS at the single and few molecules level is still very limited, and the promised applications are far from being realized. Here we report EFs as high as the most intense hotspots in previous work yet achieved in a reproducible and well controlled manner, that is, electromagnetic EFs (EMEF) of 10^9~10 with an error down to 10^+/-0.08 from gold nanospheres on atomically flat gold planes under radially polarized (RP) laser excitation. In addition, our experiment reveals the EF's unexpected nonlinearity under as low as hundreds of nanowatts of laser power.