Surface-enhanced Raman spectroscopy of cadmium sulfide/cadmium selenide superlattices formed on gold by electrochemical atomic-layer epitaxy

The phonon properties of ultrathin CdS/CdSe superlattice films formed on gold by electrochemical atomic-layer epitaxy are characterized by means of surface-enhanced Raman spectroscopy (SERS). Substantial (15–25 cm−1) red-shifts in the CdS phonon frequencies are observed, whereas the CdSe frequencies are essentially unaltered, indicating that substantial crystallographic strain occurs in the former, but not the latter, superlattice component. The findings demonstrate the virtues of SERS for exploring the structure of such solid–solid interfaces with unique monolayer-level sensitivity.