Growth mechanisms and thickness effect on the properties of Al‐doped ZnO thin films grown on polymeric substrates

Abstract

AbstractThe properties of Al‐doped ZnO (AZO) thin films deposited by pulsed DC magnetron sputtering under various target power on polyethylene terephthalate (PET) substrates have been investigated. In situ and real‐time spectroscopic ellipsometry (1.5–6.5 eV) has been employed to study the optical properties of the AZO films as well as the growth mechanisms taking place. With X‐ray diffraction technique under grazing‐incidence geometry, the structural characteristics profiles of the AZO films have been depicted. Nanoindentation measurements revealed information about the mechanical properties of the films and have been correlated to the conductivity measurements towards growth insights understanding. As results have shown, the increase of target power led to the increase of the carrier density as well as the hardness of the AZO films possibly both ascribed to dislocations induced. The stress during the deposition of AZO film under high target power favoured the island growth which is possibly both connected to the formation of defects as electron traps and dislocations as electron sources. Finally, the increase of AZO film thickness led to the increase of the resistivity possibly due to the enrichment of grain boundaries with defects as electron traps.