Study on the in-line sputtering growth and structural properties of polycrystalline ZnO:Al on ZnO and glass

This work endeavors to develop a better understanding of the growth of aluminum doped zinc oxide (ZnO:Al) films under relevant sputtering conditions that after etching yield good light trapping structures for use in thin-film silicon solar cells. The growth and etching characteristics of films grown on various substrates, including texture etched ZnO:Al, ZnO single crystals, and glass, are examined. ZnO:Al is shown to grow quasi-epitaxially on the textured ZnO:Al surface. While the new ZnO:Al growth maintains topographical features, similar roughness, and c-axis orientation, the sites of craters formed during etching are altered. The inclusion of a buffer layer between the textured ZnO:Al and the new ZnO:Al is shown to reset the c-axis. Growth and etching characteristics of ZnO:Al films on glass indicate that the columnar c-axis oriented grains are primarily Zn-terminated. A ZnO:Al growth model is proposed to explain the observed differences between the various substrates.

► Growth and etching characteristics of ZnO:Al on various substrates examined. ► Quasi-epitaxial growth of ZnO:Al on previously textured ZnO:Al. ► Primarily Zn-terminated c-axis grains when sputtered at solar cell relevant conditions. ► Growth model proposed to explain differences in growth and etching behavior.