Ce, Eu incorporation through doping of ALD-ZnO thin films for enhancing their photoluminescent properties

Abstract Nanostructured ZnO nanoarrays deposited on silicon oriented substrates is a very promising area in the study of the control of physicochemical properties, in which photoluminescence plays a crucial role. This optical property inherent to ZnO, can be favorably modified through the inclusion of doping elements, with the purpose of appropriately modifying their optical absorption and luminescence. Following this objective, in the present work we present the development of Zn _{(1− x – y )} Ce _{( x )} Eu _{( y )} O nanostructured thin films. The samples were produced in two steps process by atomic layer deposition technique followed by a solvothermal synthesis. The purpose of Cerium and Europium incorporation into the ZnO compound is to enhance the photoluminescence in ZnO thin films. In a first stage textured thin films were obtained from diethylzinc at a temperature of 190 °C and a pressure of 3.29 × 10 ⁻⁴ atm, on silicon substrates (111). Subsequently, the perpendicular growth of nanostructures was induced under a solvothermal process, where Zn(NO ₃ ) ₂ was used as Zn precursor and hexamethylene-tetramine operating as a dual-ligand to promote the linking of Zn ²⁺ ions. The growth of cerium-europium ZnO nanostructures was promoted with Ce(C ₂ H ₃ O ₂ ) ₃ ·H ₂ O and Eu(NO ₃ ) ₃ ·5H ₂ O. The obtained Zn _{(1– x – y )} Ce _{( x )} Eu _{( y )} O nanostructured thin films, were examined through SEM-microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and photoluminescence studies. The attained results show that it is feasible to produce Ce–Eu-doped ZnO nanostructures with tailored photoluminescence and crystal size. Interestingly the Ce–Eu doping induces a strong shift in comparison to the typical UV emission of ZnO; an effect that can be related with the increase of lattice defects in ZnO.