Strategies for novel transparent conducting sol–gel oxide coatings

Transparent conducting coatings of doped SnO2 and Zn2SnO4 have been deposited by the sol–gel technique on borosilicate and alumosilicate glass substrates, respectively. As films of SnO2 : Sb (ATO) show some intrinsic drawbacks, which are discussed in this report, alternative dopants for SnO2 such as Ta, Nb and W, were examined concerning the electrical and optical properties of the deposited coatings. In this way, coatings with resistivities on the order of 3 × 10− 2 Ω cm characterized by much higher charge carrier mobilities than for SnO2 : Sb and a transmission of > 85% were realized. In the search for ternary compounds (AxByOz), coatings in the system ZnO–SnO2 were examined, focusing on the fabrication of meta zinc stannate (Zn2SnO4). Coatings made from tin alkoxides yielded monophasic materials with high crystallinity and good morphological properties. By post-annealing, a resistivity of 0.4 Ω cm with charge carrier mobilities of up to 7 cm2/Vs were obtained. Therefore, the development of the coating solution is as crucial as the elaboration of the heat treatment procedure of as-deposited films in order to obtain pure Zn2SnO4 phase coatings without any impurity phases.