Toward High-Contrast Atomic Force Microscopy-Tip-Enhanced Raman Spectroscopy Imaging: Nanoantenna-Mediated Remote-Excitation on Sharp-Tip Silver Nanowire Probes

Abstract

The tip-enhanced Raman spectroscopy (TERS) imaging technique is designed to provide correlated morphological and chemical information with a nanoscale spatial resolution by utilizing the plasmonic resonance supported by metallic nanostructures at the tip apex of a scanning probe. However, limited by the scattering cross sections of these nanostructures, only a small fraction of the incident light can be coupled to the plasmonic resonance to generate Raman signals. The uncoupled light then directly excites background spectra with a diffraction-limited resolution, which becomes the background noise that often blurs the TERS image. Here, we demonstrate how this problem can be solved by physically separating the light excitation region from the Raman signal generation region on the scanning probe. The remote-excitation TERS (RE-TERS) probe, which can be fabricated with a facile, robust and reproducible method, utilizes silver nanoparticles as nanoantennas to mediate the coupling of free-space excitation light to propagating surface plasmon polaritons (SPPs) in a sharp-tip silver nanowire to excite Raman signals remotely. With this RE-TERS probe, a 10 nm spatial resolution was demonstrated on a single-walled carbon nanotube sample, and the strain distribution in a monolayer molybdenum disulfide (MoS2) was mapped.

Engineering photonic environments for two-dimensional materials

“…To date, more than 600 potential 2D materials have been predicted to be able to exist stably [2,3]. They received extensive attention from researchers due to their fascinating mechanical [21], optical [22,23], and thermal properties [24,25]. The atomically thin structure serves as a natural quantum well which can confine the EM fields leading to strong light-matter interactions [26,27].…”

Advanced Characterization Methods for Electrical and Sensoric Components and Devices at the Micro and Nano Scales

“…As a final consequence, the resolution of all described methods scales with the tip size: the sharper the tip, the better the local resolution and the signal amplification due to increased local fields, which is reflected by the vivid development ongoing in the field of tips and cantilevers …”

Probing plasmonic excitation mechanisms and far-field radiation of single-crystalline gold tapers with electrons

“…One of the most established and widely used nanostructures are conically shaped metallic tapers, due to their practical application as waveguides or nanoantennas in scanning near-field optical microscopy (SNOM) [7,[15][16][17][18][19][20][21][22][23] or as an ultrafast photoemission source in point-projection microscopes [24][25][26][27][28][29][30][31][32][33].…”