Structural and luminescence correlation of annealed Er-ZnO/Si thin films deposited by AACVD process

Abstract

Er doped ZnO thin films have been synthesized from zinc acetates dihydrate (C4H6O4Zn·2H2O) 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 °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 (2H11/2, 4S3/2 → 4I15/2 transitions) gradually increased with increasing annealing temperature. Also, the local structure of Er changes to a pseudo-octahedral structure with C4v 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.