Zinc Oxide Films Doped with Aluminum, Gallium or Tin Prepared by Dip Coating Process Using Ethanol Solution

Transparent conducting films of aluminum-, gallium or tin-doped and undoped zinc oxide were fabricated by dip coating process and post-deposition annealing in reducing gas atmosphere. Films were fabricated using zinc acetate and diethanolamine (stabilizer) with aluminum chloride hexahydrate, gallium chloride or tin (IV) chloride dissolved in ethanol. Dip coating and heating at 600°C in air were repeated ten times before annealing at 600°C in N2-0.1%H2. The average film thickness was 240 nm. The average visible transmittance exceeded 80%. Approximately 1 at.% of aluminum- or gallium-doping remarkably increased the carrier electron concentration and lowered the mobility. The lowest resistivity (6.57×10-3 Ω∙cm) was achieved by doping of 0.8 at.%Al; the carrier electron concentration, the movility and the average visible transmittance were, 3.6×1019 cm-3, 28 cm2∙V-1∙s-1 and 85%, respectively. Gallium-doping resulted in the lowest resistivity (8.09×10-3 Ω∙cm) at 1 at.%Ga with the carrier concentration of 2.9×1019 cm-3 and the mobility of 25 cm2 V-1 s-1. Tin doping increased the resistivity. The resistivities, carrier electron concentrations and mobilities were compared with reported values deposited by other deposition process.