Estudo das propriedades estruturais e ópticas do sistema ZnO@ZnS core-shell, obtido pelo método solvotérmico assistido por microondas

Abstract

Nanostructured semiconductor II-VI group were thoroughly investigated because of their unique photophysical properties. Among the most studied compounds we can highlight ZnO and ZnS which belong to semiconductors, II-VI group and exhibit band direct gaps (3.4 and 3.7 eV, respectively) and large exciton binding energies (60 and 40 meV, respectively) making them suited for optoelectronic applications. Moreover, this materials are abundant and stable in nature. In this dissertation, we report a experimental study of ZnO@ZnS core-shell prepared by a microwave-assisted solvothermal method (MAS). The synthesis parameters such as, synthesis time, precursor concentration, and temperature were xed. In order to investigate the e ect of the shell on the structural and optical properties, the samples were grown with two di erent solvents: water (H O) and ethylene glycol (EG). The characterizations of the samples were performed by X-ray di raction, absorption spectroscopy in the UV-Vis range, scanning electron microscopy, and photoluminescence spectroscopy. Then, the results show through the X rays di ractions (XRD) the formation of wurzita phase for both material core (ZnO) and for shell (ZnS), however the crystallinity degree of ZnS shell are too low. A more homogeneous coating of ZnS on the surface of ZnO for sample obtained in EG, clearly seen in the SEM images was observed. For the results of PL, the system decorated obtained using both solvents were appropriate to form a type-II band alignment, leading to a possible application in solar cells.