Annealing effects on the photoluminescence of terbium doped zinc oxide films

Terbium doped zinc oxide (Tb:ZnO) films were deposited by radio frequency magnetron sputtering on (100) single-crystalline silicon substrates at low temperature (TS = 100 °C). In this work, structural changes, optical properties and the associated photoluminescence (PL) responses are analyzed upon the annealing treatments. Post-annealing treatments from annealing temperature Ta = 400 °C up to 1000 °C by steps of 100 °C were performed. Chemical analyses by energy dispersive X-ray spectrometry measurements showed a constant dopant concentration of 3 at.%. Up to 600 °C, the band gaps (Eg) decreased with Ta from 3.44 down to 3.37 eV. Above 600 °C, the band gap raised from 3.37 up to 3.42 eV (for 900 °C). Depending on Ta, a bi-axial stress was found varying from a compressive value of − 0.21 GPa (400 °C) down to a tensile value of 0.05 GPa (1000 °C). PL mechanisms of the Tb:ZnO film are then discussed.