Investigation of p-type behavior in Ag-doped ZnO thin films by E-beam evaporation

Ag-doped ZnO (ZnO:Ag) thin films were grown on glass substrates by E-beam evaporation technique. The structural, electrical and optical properties of the films were investigated as a function of annealing temperature. The films were subjected to post annealing at different temperatures in the range of 350-650 oC in an air ambient. All the as grown and annealed films at temperature of 350 oC showed p-type conduction. The films lost p-type conduction after post annealing treatment temperature of above 350 oC, suggesting a narrow post annealing temperature window for the fabrication of p-type ZnO:Ag films. ZnO:Ag film annealed at 350 oC revealed lowest resistivity of 7.25 x 10-2 Ω cm with hole concentration and mobility of 5.09 x 1019 cm-3 and 1.69 cm2/V s, respectively. Observation of a free-to-neutral-acceptor (e,Ao) and donor-acceptor-pair (DAP) emissions in the low temperature photoluminescence measurement confirms p-type conduction in the ZnO:Ag films.