Boron-doped zinc oxide thin films prepared by sol-gel technique

Multilayer transparent conducting boron-doped zinc oxide films have been prepared on glass substrates by the sol gel dip coating process. Zinc acetate solutions of 0.4 M in isopropanol stabilized by diethanolamine and doped with boron tri-i-propoxide were used. Each layer was fired at 400–650∘C in a conventional furnace for 30 min. Selected samples were vacuum annealed at 400–450∘C for 1 h to improve their electrical properties. The electrical resistivity curve with doping shows a minimum around 0.8 at.%. Excess boron caused a drop of the carrier mobility without acting as donors. Post-deposition annealing sequence was crucial for dopant partial regeneration. Films with an average optical transmittance exceeding 90% can be achieved reproducibly.