Spectroscopic Effects of Lattice Strain in InP/ZnSe and InP/ZnS Nanocrystals

An elastic continuum model has been used to analyze the effects of lattice mismatch on the spectroscopy of InP/ZnSe and InP/ZnS nanocrystals. Lattice strain affects the vibrational frequencies and band energetics and therefore the Raman and electronic spectra, respectively. The band energetics are determined from bulk values and calculated lattice strains and are used with an effective mass approximation model to obtain wave functions and calculated exciton energies. Recently reported Raman spectroscopy results on InP/ZnSe and InP/ZnS nanocrystals (Rafipoor et al., J. Chem. Phys. 2019, 151, 154704) are analyzed using this model. The results show semiquantitative agreement between experimental and calculated Raman frequencies and exciton energies in the case of Inp/ZnSe nanocrystals having more than a two-monolayer shell. This indicates that with this small lattice mismatch (3.5%), a coherent core/shell interface is obtained. In contrast, the InP/ZnS lattice mismatch is much larger, 8.3%. In this case, the experimental results show best agreement with calculations in which lattice strain is ignored. This indicates that the interfaces in InP/ZnS nanocrystals are largely incoherent.