Effects Of Rapid Thermal Annealing On The Structural, Optical, And Electrical Properties Of Zno/Ag/Sno2 Tri-Layer Films

ZnO 50 nm/Ag 10 nm/SnO2 50 nm (ZAS) tri-layer films were deposited on a glass substrate by RF and DC magnetron sputtering and then underwent rapid thermal annealing in a low vacuum of 1x10(-3) Torr to investigate the effects of post-deposition annealing on the optical and electrical properties of the films. The peak intensity of the XRD pattern related to the ZnO (002) peak of the annealed films was higher than that of the as-deposited film and the full width at half-maximum of the ZnO (002) diffraction peak of the annealed films was smaller than that of the as-deposited film. Therefore, the crystallinity of ZnO was improved by rapid annealing. However, crystallization of the Ag interlayer and SnO2 surface layer were not significantly affected by the annealing temperature, compared with the ZnO bottom layer. From the observed electrical properties and optical band gap, it was concluded that the blue shift in the optical band gap is related to the carrier density of the films. The band gap increased from 4.19 eV to 4.24 eV, with the carrier density increasing from 7.09 x 10(21) cm(-3) to 7.77 x 10(21) cm(-3). However, the film annealed at 450 degrees C showed a decreased band gap energy of 4.17 eV due to the decreased carrier density of 6.80 x 10(21) cm(-3). The as-deposited ZAS films showed a sheet resistance of 11.0 Omega/square and a visible transmittance of 80.8%, whereas the films annealed at 450 degrees C had a higher visible transmittance of 82.3% and a lower sheet resistance of 6.55 Omega/square. The results indicate that ZAS thin films may be possible substitutes for conventional Sn-doped In2O3 transparent electrodes in various optoelectronic devices.