Bulg. J. Phys. 40 (2013) 237–246 Influence of the Annealing on the Structural, Optical and Electrical Properties of Transparent Conductive ZnO:Al/Ag/ZnO:Al Multilayer Stacks * K. Lovchinov 1 , M. Petrov 1 , O. Angelov 1 , H. Nichev 1 , D. Karashanova 2 , D. Dimova-Malinovska 1 1 Central laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee Blvd., 1784 Sofia, Bulgaria 2 Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl.109, 1113 Sofia, Bulgaria Abstract. The multi-layer stacks ZnO:Al(20nm)/Ag(x)/ZnO:Al(20nm) are prepared by r.f. magnetron sputtering on glass substrates with two different thicknesses of the middle Ag film, x = 16 and 20 nm. The ZnO:Al layers are deposited in Ar+H2 atmosphere and the Ag layer in pure Ar. The sub- strates are not heated during the deposition of films. Two different stack struc- tures are annealed in N2+H2 at 180 ◦ C for 50 min: the two-layer ZnO:Al/Ag(x) which is covered by the top ZnO:Al film after annealing and the three-layer ZnO:Al(20nm)/Ag(x)/ZnO:Al(20nm). Structural, optical and electrical proper- ties of the as-deposited and annealed structures are studied. The TEM, SEM and AFM analysis confirm the semi-continuous structure of the middle Ag layer in the as-deposited stacks and formation of Ag grains after annealing. The grains size increases with the thickness of the Ag layer and after anneal- ing. The transmittance and reflectance spectra of the as-deposited and an- nealed stacks demonstrate bands associated with Ag electrons plasma oscil- lations and d-shell electron inter-band transitions. The results are analyzed and explained by the changes in the grains size, interaction between them and overlapping between the quadrupolar and dipolar plasmon resonances. The as- deposited stacks ZnO:Al(20nm)/Ag(x)/ZnO:Al(20nm) demonstrate low resis- tivity – 9.0 × 10 −5 Ohm.cm (x = 16) and 4.0 × 10 −5 Ohm.cm (x = 20 nm). The resistivity increases slightly after annealing. The study demonstrates potential for application of multilayer structures ZnO:Al(20nm)/Ag(x)/ZnO:Al(20nm) for x = 16 nm and 20 nm at back side conductive electrode with plasmonic properties for improvement of the thin film solar cells with increased light har- vesting PACS codes: 73.63Bd, 78.20.-e, 71.45Gm, 73.90.+f ∗ Talk given at the Second Bulgarian National Congress in Physics, Sofia, September 2013. 1310–0157 c  2013 Heron Press Ltd. 237