Redistribution of Tb and Eu ions in ZnO films grown on different substrates under thermal annealing and its impact on Tb-Eu energy transfer

•Annealing at 900 °C of Tb,Eu-ZnO/Si films causes formation of Tb oxides and silicates.•RE ion enrichment of n-ZnO/p-Si interface is explained by ion drift in electric field.•Annealing at 900 °C of Tb,Eu-ZnO/Al2O3 films results in formation of Tb oxides and ZnAl2O4.•Energy transfer from Tb3+ to Eu3+ is observed in Tb2O3 and TbxEuySiO7 phases.•A theoretical approach for Tb3+ and Eu3+ energy spectra calculation is developed.