Structural and luminescence correlation of annealed Er-ZnO/Si thin films deposited by AACVD process
Résumé
Er doped ZnO thin films have been synthesized from zinc acetates dihydrate (C4H6O4Zn center dot 2H(2)O) and Erbium tris (2,2,6,6-tetramethyl-3,5-heptadionate) (Er(TMHD)(3)) by aerosol assisted chemical vapor deposition AACVD atmospheric pressure technique. Films were deposited in the temperature range of [370-500 degrees C] on Si (1 1 1) substrate. Nano-disk shaped grains were grown on the top of the film surface. The morphology of the as-deposited films was found to be dependent on the substrate temperature. After annealing in air atmosphere, XRD patterns revealed a highly oriented c-axis Er:ZnO films with hexagonal wurtzite structure without any second phase. Under 488 nm excitation, the intra 4f-4f green emission (H-2(11/2), S-4(3/2) -> I-4(15/2) transitions) gradually increased with increasing annealing temperature. Also, the local structure of Er changes to a pseudo-octahedral structure with C-4v symmetry. The ZnO film with 2.504 at.% Er3+ doping has the best crystalline structure and the best resolved PL spectra. Using 325 nm excitation, all the samples showed an ultraviolet emission centered at 380 nm originating from a near band EDGE emission and a broad band green emission centered at 520 nm from deep levels. The optical response was correlated with crystallinity of the synthesized thin films. (C) 2013 Elsevier B.V. All rights reserved.