Influence of annealing on the optical, structural and electrical properties of ZnO:Al/Ag/ZnO:Al multilayer stack structures

Multilayer stack structures ZnO:Al(20 nm)/Ag(x)/ZnO:Al(20 nm) with different thickness of the middle Ag(x) layer - x = 6 nm, 10 nm, 12 nm, 16 nm and 20 nm, were prepared by r.f. magnetron sputtering. The ZnO: Al and Ag layers were deposited by magnetron sputtering on glass substrates without heating. The two-layer structures ZnO: Al(20)/Ag(x) were annealed in N-2 + H-2 at 180 degrees C, 50 min., and then capped by the top ZnO: Al(20 nm) layer. The optical, structural and electrical properties were studied of the as-deposited and of the annealed three-layer stacks. The TEM, SEM and AFM analyses demonstrated changes of the stack structure with the Ag film thickness and after annealing. The transmittance and reflectance spectra revealed bands of Ag electrons plasma oscillations and inter-band d-shell Ag electrons which were red-shifted after annealing. The as-deposited structures had low resistivity (1x10(-3) to 4x10(-5) Omega cm), which decreased with the thickness of the Ag film due to the change in the carrier transport mechanisms. The value of the resistivity increased after annealing.