Al L2,3 near edge structure captures the dopant activation and segregation in Al-doped ZnO films.

Aluminum-doped zinc oxide (AZO) films have been synthesized using reactive high power impulse magnetron sputtering (HiPIMS) in a wide range of Al contents, 0.6–14.7 at.%. The film structure and microstructure investigated by X-ray diffraction and transmission electron microscopy evolves from nanocrystalline columnar film towards ultrafine nanocrystalline films of wurtzite ZnO structure upon increasing the Al content. Electrical properties measured by 4-point probe and Hall effect setups revealed that effective doping maybe achieved up to 3 at.% Al by using HiPIMS. Most importantly, optical transmittance and electronic structure measurements at the Al L 2,3 of electron energy loss near edge structure (ELNES) contain signatures of dopant activation, and dopant segregation that may serve to investigate on the origin of electrical properties degradation and to optimize the electrical properties of AZO films. • Al-doped ZnO films synthesized by reactive HiPIMS of preserved wurtzite structure up to 14.7 at.% Al • Increasing the dopant content above 1 at.% Al decreases the crystallinity. • High density of charge carriers is induced by Al doping up to 3 at.% Al. • Al contents above 3 at.% inactivate a significant fraction of Al dopant. • Electronic structure at the Al L 2,3 edge can be used to extract the fractions of active/inactive Al dopant. [ABSTRACT FROM AUTHOR]