Metal-oxide based material such as zinc oxide (ZnO) has attracted great interest for theoretical and experimental studies, and highly applicable for photonic, optoelectronic and future spintronic devices, such as being a semiconductor host for diluted magnetic semiconductor (DMS). ZnO also has the advantage of a larger exciton binding energy (~ 60 meV) which assures more efficient excitonic emission at higher temperatures. In this talk, optical properties of ZnO based thin films towards optoelectronic and spintronic devices will be discussed.

Here, we will discuss the strong modification of the optical properties of ZnO thin film through doping and post deposition treatment, as an example by hydrogen annealing. We use the as-prepared amorphous and crystalline ZnO films grown physical vapor deposition technique such as by pulse laser deposition (PLD) and unbalanced magnetron sputtering. We found that hydrogen annealing treatment promote the significant strong green emission as directly shown by UV light exposure and further confirm by photoluminescence spectra. Spectroscopy ellipsometry analysis also supports the strong modification of the optical properties of ZnO film by Hydrogen annealing treatment. This study demonstrated the enhancement of green emission and the evolution of optical properties driven by
surface and structure modification.

Furthermore, to study the effect of atomic doping, we will discuss the excitonic states and related optical properties of pure and Cu doped ZnO films. The influence of electronic environment by selecting the different substrate, that is Pt (metal) and quartz (insulator) will be demonstrated as well. This study shows the weak electronic interactions between ZnO film and quartz substrate, in contrast to the ZnO film and Pt by considering the electronic blocking through the spontaneous recombination of valence electrons from Pt to ZnO film. As a function of Cu doping, we observe localized interband transition and screening effects on exciton for both systems
(ZnO film on Pt and ZnO film on quartz). Our results show the importance of itinerant electron from substrate and doping to strongly tune and modify the excitons and the optical conductivity of the wide bandgap semiconductor.