Variation in the structural and optical properties of ZnSe/ZnS core/shell nanocrystals with shell thickness

ZnSe/ZnS nanocrystals were synthesized using the TOP/TOPO mild chemistry approach. Shell thickness was varied by changing the shell precursor concentration. Corresponding structural variation was investigated monitoring X-ray diffraction peak shifts. High-resolution transmission electron microscopy images revealed that ZnSe/ZnS nanocrystals with thick shell have crystalline imperfections such as stacking faults due to the heavy compressive strain by ZnS shell. The red- and blue-shifts in photoluminescence (PL) spectra according to the shell thickness were identified to originate from the extension of electron wave function of ZnSe to the shell and the compressive strain of the core, respectively. The PL spectra also showed increase and decrease in the peak intensity with shell thickness due to the surface passivation effect and stacking faults, respectively.