Investigating the Local Bonding Structure of Amorphous Zinc Tin Oxide to Elucidate the Effect of Altering the Intercation Ratio

In this paper, the local bonding structure in amorphous zinc tin oxide (a-ZTO) is probed using a combination of XANES and EXAFS techniques at the Zn and Sn K-edges to gain insight into charge carrier generation in the material. a-ZTO is prepared using two growth methods; spray pyrolysis and magnetron sputtering. It is seen that a-ZTO grown by magnetron sputtering shows no changes in the chemical environment as the cation ratio is varied; meanwhile, XANES analysis of spray pyrolysis grown samples shows alterations to spectra likely due to the effects caused by different precursors. Although a slight shift in Sn-O bond length is visible between magnetron sputtered and spray grown samples, no correlation could be discerned between bond length and variation in cation ratio. It is concluded that a-ZTO, while amorphous over longer ranges, is locally composed of ZnO and SnO₂ "building blocks". An alteration in the cation ratio changes the hybridization at the conduction band minimum, resulting in the observed variation in the mobility, charge carrier concentration, and bandgap.