Abstract:
We are studying structural, optical, electrical and magnetic properties of rare earth doped Zinc Oxide (ZnO) thin films. In our present work, Erbium (Er) is used as dopant and pulsed laser deposition (PLD) technique for growing films. Our initial XRD results show single phase Er:ZnO for all samples. The low temperature (4K) photoluminescence spectrum of these films disclosed that all the as-grown samples are optically inactive for the particular emission (4S3/2→4I15/2) of Er, irrespective of their growth conditions. After annealing at 750°C for 40 minutes in Argon atmosphere, samples that were grown at 600°C and 750°C substrate temperatures show notable emission for intra shell (4f) transitions of Er. Whereas, all the vacuum grown samples remain optically in active even after annealing, under the same conditions. H-plasma treatment at room temperature was performed on the annealed samples grown at 600°C substrate temperature to investigate that this intra 4f shell transitions is surface or bulk phenomenon. We found a significant improvement in the intensity of the near band edge emission, but the emission from the intra 4f shell transition of Er was totally absent. Our observations indicate that intra shell (4f) transitions of Er happen only in the optical centres present at the sample's surface.