Effect of a ZTO buffer layer on the structural, optical, and electrical properties of IGZO thin films

Transparent and conducting InGaZnO4 (IGZO) thin films were deposited by RF magnetron sputtering on zinc tin oxide (ZTO) coated glass substrates to investigate the effect of the ZTO buffer layer on the structural, optical, and electrical properties of the IGZO/ZTO films.X-ray diffraction (XRD) analysis revealed that although all the films were in the amorphous phase, IGZO 90 nm/ ZTO 10 nm bi-layered films had a lower resistivity (1.1×10−2 Ωcm) than the other films prepared in this study. The enhanced optical transmittance of IGZO 80 nm/ZTO 20 nm films (85.5%) was attributed to the two-fold lower RMS roughness of these films than that of IGZO single films, because a flat surface reduces optical scattering and absorption at the film surface.These results indicate that a ZTO thin film is an effective buffer layer that can enhance the optical transmittance and electrical conductivity of the IGZO upper film.