Selective Anion Manipulation for Controlling the Thermoelectric Properties of Epitaxial SnO2 Films on r-Al2O3

Abstract

Introducing defects is one of the promising approaches for enhancing the thermoelectric property. In this study, we substantially reduce thermal conductivity while maintaining a high thermoelectric power factor (PF) by selectively manipulating O^2– anion in domain-engineered SnO₂ with conduction and valence bands mainly composed of Sn 5s and O 2p orbitals, respectively. Ion implantation can generate O defects more easily than Sn defects, resulting in a small impact on the Sn 5s conduction band and the formation of the O defect resonant level. The lattice thermal conductivity of the arsenic-implanted epitaxial SnO₂ films with the manipulated O^2– anions (2.6 Wm^–1 K^–1) is approximately half that of Sb-doped films without them (4.7 Wm^–1 K^–1), while the maximum PF of arsenic-implanted epitaxial SnO₂ films remains relatively high owing to the high Seebeck coefficient originating from an effective mass increase. This selective O^2– anion manipulation is an outstanding methodology of selectively causing thermal conductivity reduction while maintaining a high PF.