Thermal transport properties of polycrystalline tin-doped indium oxide films

Thermal diffusivity of polycrystalline tin-doped indium oxide (ITO) films with a thickness of 200 nm has been characterized quantitatively by subnanosecond laser pulse irradiation and thermoreflectance measurement. ITO films sandwiched by molybdenum (Mo) films were prepared on a fused silica substrate by dc magnetron sputtering using an oxide ceramic ITO target (90 wt % In2O3 and 10 wt % SnO2). The resistivity and carrier density of the ITO films ranged from 2.9 x 10(-4) to 3.2 x 10(-3) Omega cm and from 1.9 x 10(20) to 1.2 x 10(21) cm(-3), respectively. The thermal diffusivity of the ITO films was (1.5-2.2) x 10(-6) m(2)/s, depending on the electrical conductivity. The thermal conductivity carried by free electrons was estimated using the Wiedemann-Franz law. The phonon contribution to the heat transfer in ITO films with various resistivities was found to be almost constant (lambda(ph) = 3.95 W/m K), which was about twice that for amorphous indium zinc oxide films. (C) 2009 American Institute of Physics. [DOI:10.1063/1.3093684]