Baric properties of CdSe-core/ZnS/CdS/ZnS-multilayer shell quantum dots

The model of spherical quantum dot of the core/multilayer shell type, which is subjected to external comprehensive pressure, is constructed taking into account the mismatch between the lattice parameters of the contacting layers and the pressure due to the curvature of the surface. Within the method of the deformation potential, the influence of external pressure on the band structure of CdSe-core/ZnS/CdS/ZnS-shell quantum dot was investigated. It is shown that by changing the thickness of the shell layers and the amount of pressure, it is possible to change the width of the optical band gap of quantum dot in a wide range. It was found for the first time that in the case of small CdSe QD cores (less than 2.5 nm) there is a critical value of comprehensive pressure, above which the value of baric coefficient decreases abruptly. It is shown that an increase in the thickness of CdS layer in the three-layer ZnS/CdS/ZnS shell leads to a decrease in the critical pressure, and in the two-layer ZnS/ CdS shell leads to an increase in the critical pressure. It is established that in the case of a three-layer shell for small radii of cores (less than 2.5 nm) at pressure greater than 16.5 kbar there is an anomalous dependence of the energy of electron in the ground state and, accordingly, the width of the optical band gap on the core radius: increasing the radius of core leads to an increase in the width of the optical band gap of quantum dot.