Raman spectroscopy of PbTe/CdTe nanocrystals

We studied the evolution of Raman signals stemming from colloidal PbTe/CdTe nanocrystals (NCs). The NCs were grown using the cation exchange method and samples having different amounts of CdTe as shell material were investigated. The observed Raman bands are correlated to pure tellurium modes and after introduction of CdTe its longitudinal optical (LO) mode becomes also visible. The tellurium modes' intensity rapidly decreases after cationic exchange due to the chemical bonding of the vacant tellurium atoms.