Optimization and Properties of Zn Doped Indium Oxide Films on Plastic Substrate

In this report, optimization of the Zn content in Zn doped indium oxide (IZO) films deposited on plastic substrates at low temperature (20°C) was investigated in relation to variation of the Zn content from 0 to 15.9 at%. In the series of IZO films, 12.2 at% Zn doped indium oxide films, (IZO(12.2)), showed the lowest resistivity (2.9×10-4 Ωcm). The resistivity of IZO(12.2) films deposited on 100-µm-thick polycarbonate foil was approximately one half of that of ITO films (6×10-4 Ωcm) deposited under comparable conditions. IZO(12.2) films exhibited the lowest resistivity, high transmittance of over 85%, a rapid etching rate and good alkaline durability. The reason for rapid etching rate originates from the amorphous structure of IZO films. The thermal property of IZO(12.2) evaluated by a differential scanning calorimeter (DSC) clarified that the phase transformation from amorphous to crystalline began at 350°C, which meant the structure of IZO(12.2) remained amorphous for a practical temperature of the plastic substrate. Optical gap and Hall measurements revealed that the carrier density was decreased after annealing, whereas, the mobility was increased in relation to a trade off with the carrier density.