Ultrathin Sb-implanted ZnO transparent electrodes synthesized by MOCVD liquid precursors.

ZnO adopts the hexagonal close packing wurtzite structure in which oxygen ions are stacked along the [001] direction and Zn2+ cations occupy one-half of the tetrahedral sites. The presence of lattice defects consisting of oxygen vacancies and involving interstitial (Zn2+ -2e-) pairs and cation and anion vacancies makes ZnO an intrinsic n-type semiconductor with a band-gap of ~3.3 eV. The synthetic procedure adopted to obtain ZnO and/or the presence of dopants within the ZnO lattice strongly influence the resistivity. Thin films of ZnO have a large number of important applications as solar cells, optical waveguides, varistors, gas sensors, photoluminescent devices etc. They have been synthesized using a large variety of techniques. Among them metal organic chemical vapor deposition (MOCVD) using liquid precursors to grant constant evaporation and mass-transport rates for given source temperatures ensures excellent deposition reproducibility. In the present investigation we report on MOCVD of ZnO films from liquid precursors that have subsequently implanted with different values of Sb content. Deposition experiments, in a low-pressure horizontal hot-wall reactor, on ITO conductive glasses, resulted in 60-200 nm ZnO films, in our reaction conditions. XRD measurements provided evidence that they consist of hexagonal, (002) and (10l) oriented, crystals. UV-Vis spectra showed that the transmittance of as deposited films in the visible region is about 90% and the current-voltage characteristics performed on all the transparent diodes showed a rectifying behavior.