Investigation of the SERS spectra of copper phthalocianine adsorbed on gallium phosphide substrates

TL;DR

This study investigates the SERS spectra of copper phthalocyanine on gallium phosphide, revealing forbidden lines due to quadrupole interactions and electric field enhancements characteristic of semiconductor substrates.

Contribution

It provides new insights into the mechanisms of SERS on semiconductor surfaces, highlighting the role of quadrupole interactions and tangential electric field enhancements.

Findings

Detection of forbidden lines in SERS spectra

Strong quadrupole light-molecule interaction observed

Enhanced tangential electric field components on semiconductor surface

Abstract

The SERS spectra of the phthalocianine molecule, adsorbed on the gallium phosphide substrate are investigated. It is demonstrated that there appear strong lines, which are forbidden in usual Raman scattering. Analysis of the spectra indicates that these lines are associated with a strong quadrupole light-molecule interaction and also by a strong enhancement of the tangential components of the electric field on the surface. As it was demonstrated earlier, the last effect is characteristic for SERS on semiconductor and dielectric substrates, where there is the enhancement not only of the normal, but of the tangential components of the electric field on the surface.