Water vapor barrier properties of Si–Zn–O/Al multilayer structures

Abstract

Single-layer Si–Zn–O (SZO) and multilayer SZO/Al films are deposited as water vapor barriers on polyimide (PI) substrates, using magnetron sputtering with SiO2–ZnO composite and Al targets. The effect of negative substrate bias voltage (Vb) on the microstructure and water vapor barrier properties of the single layer SZO and multilayer SZO/Al films is investigated. The as-deposited SZO film is found by X-ray diffraction analysis to be amorphous. For deposition at Vb=0V, the SZO film has a columnar structure and rough surface morphology; the Al film exhibits pinholes on the surface. When moderate bias voltages (Vb=−50V for SZO and −70V for Al films) are applied during deposition, a dense SZO film with smooth surface morphology and a pinhole-free Al film are obtained. An SZO/Al multilayer film shows better water vapor barrier performance than a single-layer SZO, which could be further enhanced by application of Vb to the substrate during film growth.