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 Sp(T) = AT + (B/T) + C with fitting parameters A, B and C. We define a percolation index as Γ300 = |B/(AT 2)| at T = 300 K, the doping dependence of which is found to be related to that of the power factor P300 = S 2 300 • σ300 in the ICO films. Similar correlations are also shown in bulk-systems composed of rare-earth metal oxides.

High-mobility transparent conductive thin films of cerium-doped hydrogenated indium oxide

“…2) Various dopants of metal species such as W, 3) Zr, 4) and Mo 5) have been used to dope polycrystalline In 2 O 3 films to improve the crystallinity, thereby reducing intragranular lattice defects. We have been investigating the properties of Ce-doped 6) In 2 O 3 films. That study was based on two factors with their corresponding effects: (i) the effective ionic radius of Ce 4+ with a coordination number of 6 (0.101 nm) 7) is close to that of In 3+ with the same coordination number (0.094 nm), 7) leading to the reduction of microstrain in the vicinity of the dopant sites; (ii) the density of the oxygen vacancies can be reduced by doped CeO 2 with a large standard formation enthalpy when compared to In 2 O 3 , resulting in crystallinity improvements.…”