Structural Instability in Amorphous In-Ga-Zn-O Films Investigated by Mechanical Stress Analysis

Amorphous In-Ga-Zn-O (a-IGZO) experiences an inherent structural instability which restrict its applications in electronic devices. By utilizing an in-situ mechanical stress analysis, we characterized the phase and structural changes. The glass transition temperature, Tg(423–562°C) and fragility (18–28) in a-IGZO films were observed to ascertain quantitative criteria for the structural stability. The structural stability near Tgwas significantly reduced as the thickness decreased due to the effect of the unstable surface layer. The structural relaxation of glass below Tgwas identified as the viscous flow and densification.