X-ray absorption spectroscopy study of the local structures of crystalline Zn-In-Sn oxide thin films

The local structure of a Zn, Sn codoped In₂ O₃ thin film grown on c -plane sapphire by pulsed-laser deposition was examined by polarization-dependent x-ray absorption spectroscopy. The bixbyite film structure is both out-of-plane and in-plane oriented, and the structural results show that both Zn and Sn dopants occupy In sites. The In-O bond length is comparable to that in powder In₂ O₃. However, both Sn-O and Zn-O bonds have two distinct distances in the first shell. Some of the Zn dopants are undercoordinated and, accordingly, some isovalent Sn dopants are overcoordinated for charge balance. In addition, the results suggest that the aliovalent Sn dopants form Frank-Köstlin clusters, (2 Sn In Oi″) x, which provide enough charge carriers to explain the Hall measurements.