Importance of Local Bond Order to Conduction in Amorphous, Transparent, Conducting Oxides: The Case of Amorphous ZnSnOy.

In this report, reactive and nonreactive sputtering of amorphous ZnSnOy (a-ZnSnOy) was investigated, and extensive composition maps have been measured by X-ray photoelectron spectroscopy. The comprehensive analysis of the ((ZnO)x(SnO2)1-x) composition reveals that the best Zn/Sn ratio for high conductivity of the material can vary depending on the deposition technique utilized. Best conductivities of 225 S/cm were found to occur at x = 0.32 for reactive sputtering of a Sn target and x = 0.27 for nonreactive sputtering of a SnO2 target. These values correspond to unstable polymorphs of a-ZnSnOy, ZnSn2O5, and ZnSn3O7. Distinct local bonding arrangements have been confirmed by Raman spectroscopy.