Transparent Conducting Films in the Zn--Sn--O Tie Line

Abstract

Coatings were obtained on borosilicate glass and fused silica substrates with thicknesses of up to 230 nm from solutions with compositions along the Zn--Sn--O tie line. The preparation of the sols was accomplished by combinatorial chemistry with a robotic sample processor using different Zn^I I, Sn^I I and Sn^I V salts and alkoxides, as well as salts of different doping agents (e.g. Sb^V, Ta^V, In^I II) dissolved in various solvents and additives. The films were made by spin-coating followed by a thermal treatment in air, inert or reducing atmosphere at temperatures up to 1000°C. Except for a few cases, mixed crystalline phases of ZnO, SnO₂ and ZnSnO₃ or Zn₂SnO₄ are usually observed within the range 0.4 < [Zn]/([Zn] + [Sn]) < 0.75. Pure Zn₂SnO₄ and ZnSnO₃ coatings exhibit good optical properties with a haze <0.2% and a transmission in the visible range >85%. In contrast to literature, results obtained for similar coatings by sputtering and pulsed laser deposition, all the sol–gel coatings showed a high resistivity of ρ > 3 Ωcm even after a forming gas treatment and/or doping.