Improvement of transparent conductive properties of GZO/Cu/GZO tri-layer films by introducing H2 into sputtering atmosphere

For preparation of transparent conductive oxide (TCO)/metal/TCO tri-layer films, Cu and Ga-doped ZnO (GZO) films were respectively used as the metal and TCO layers and were deposited by magnetron sputtering at room temperature. The effect of film thickness on transparent conductive properties of single Cu films was first investigated in order to better understand the properties of tri-layer films. The results show that the resistivity, sheet resistance (Rs), average transmittance in visible light range (TVis), and figure of merit (FOM) of Cu films decrease with increasing film thickness. The investigations of effect of H2 flux on the transparent conductive properties of GZO films show that hydrogenated GZO (HGZO) films have lower resistivity and higher TVis than those of GZO films. On basis of the investigation of single Cu and GZO films, the GZO/Cu/GZO (GcG) and HGZO/Cu/HGZO (HcH) tri-layer films were prepared, and their transparent conductive properties were investigated as a function of Cu and GZO (or HGZO) layer thickness. The results show that these two kinds of tri-layer films have the best FOM at Cu layer thickness of 7 nm and GZO (or HGZO) layer thickness of 40 nm. Compared with GcG tri-layer films, HcH tri-layer films have better FOM, indicating that introducing H2 into sputtering atmosphere plays a significant role on the transparent conductive properties of the tri-layer films. In addition, bandgap (Eg) of single GZO and tri-layer films was discussed as a function of carrier concentration in the paper.