High thermal stability, electrical and optical properties of amorphous IGZO film by coating ultrathin amorphous ITO film as barrier layer

As one kind of well known amorphous transparent conductive oxide films, In–Ga–Zn–O (IGZO) based films were broadly used as electric functional layer in optoelectronic devices. As IGZO film is sensitive to temperature and oxygen, and its electrical and optical properties may probably be deteriorated after subsequent high temperature and air atmosphere. In this work, amorphous indium tin oxide (ITO) layer with two adjustable type of thickness were employed to improve the thermal stability of IGZO films. The doubled ITO/IGZO films were deposited on glass by magnetron sputtering and annealed at high temperatures subsequently to investigate its thermal stability. Accordingly, the crystal structure, optical and electrical properties of ITO/IGZO films were further studied. The XRD results demonstrated that the annealed IGZO films could keep amorphous structure, and the ITO/IGZO films were consisted of uniform small particles which showed comparable dense structure and closely integration with the glass substrate. Furthermore, the sheet resistance results indicated that the increased thickness of top ITO film could suppress oxygen and improve thermal stability of electrical property. Moreover, the transmittance in the visible range was about 85%, and showed a little increase after annealing. The protective ITO layer was found to keep improved thermal stability, good electrical and optical properties at temperatures up to 550 °C.