The Local Bonding Environment of Amorphous In-Zn-O Films Studied by X-ray Absorption Fine Structure and Total X-ray Scattering Using Synchrotron Radiation

The structure of amorphous In-Zn-O (a-IZO) thin films was investigated using X-ray absorption fine structure (XAFS) and total X-ray scattering techniques. In spite of the lack of long-range periodicity, a-IZO thin films were found to exhibit significant ordering on short length scales. It was found that indium and zinc are 6- and 4- fold coordinated with oxygen, respectively, as they are in their native crystalline structures. The InO6 and ZnO4 polyhedra were also found to exhibit edge-sharing connectivity. Although the edge-shared polyhedra had a significant distribution of bond lengths, the next-nearest neighbor metal atoms occurred at approximately the same composition found using bulk composition measurements. The wide temperature and composition range where IZO films remain amorphous is likely due to the structural frustration induced by Zn-centered tetrahedrons and In-centered octahedrons