Mechanical and structural properties of high temperature a-ITO:Sm films deposited on polyimide substrate by DC magnetron sputtering

Abstract

Amorphous ITO (a-ITO) films are well known to have very high potential application in flexible display because of their excellent surface morphology and good etchability, compared to polycrystalline ITO. However, there are some problem s such as relatively high resistivity and low durability under bending state. These poor electrical and mechanical properties of a-ITO films can be improved by elevating the substrate temperature. However, a-ITO films crystallized by heat treatment (approximately 170 °C) lose their advantages. Therefore, in this study, we try to improve the durability of a-ITO at the high temperature. ITO and Sm doped ITO (ITO:Sm) films were successfully deposited on polyimide (PI) substrates by DC magnetron sputtering using ITO targets containing different Sm ratios (doped-Sm: 0, 3, 5 and 7 wt.%). Film deposition and post-annealing were carried out at room temperature and different temperatures (170 °C and 200 °C), respectively, in a pure Ar gas atmosphere at 1.0 Pa for 1 h. The ITO:Sm films had an amorphous structure, good mechanical properties and a very flat surface morphology above the crystallization temperature of ITO films (approximately 170 °C). The mechanical properties of the ITO:Sm films were improved by increasing both Sm doping concentration and post-annealing temperature due to the alleviation of internal stress in the amorphous structure. The lowest resistivity (5.954 × 10 −4 Ω cm) was obtained for the amorphous ITO:Sm film deposited using the 3 wt.% Sm doped ITO target at 200 °C.