Thermoelectric Properties in Transparent-Conductive Cerium-Doped In₂O₃ Films

Abstract

Thermoelectric properties are studied in Ce-doped In₂O₃ (ICO) films with Ce content x up to 9 at.% prepared by dc sputtering. Films of ICO are transparent in the visible light region (transmission more than 80%), having the highest room-temperature conductivity σ₃₀₀=120 S/cm for x = 3 at.%. Thermoelectric power at room temperature S₃₀₀ is well correlated to the electron density n, showing a linear relation of S₃₀₀ vs. ln (σ₃₀₀) in the Jonker fashion. The temperature dependence of the thermoelectric power S(T) is well described in terms of a simple percolation model characterized by a formula S_p(T) = AT + (B/T) + C with fitting parameters A, B and C. We define a percolation index as Γ₃₀₀ = |B/(AT²)| at T = 300 K, the doping dependence of which is found to be related to that of the power factor P₃₀₀ = S₃₀₀²·σ₃₀₀ in the ICO films. Similar correlations are also shown in bulk-systems composed of rare-earth metal oxides.[DOI: 10.1380/ejssnt.2012.471]