Thermoelectric Properties of Amorphous Zinc Oxide Thin Films Fabricated by Pulsed Laser Deposition

Abstract

Thermoelectric properties of non-doped amorphous zinc oxide (ZnO) thin film were studied at between room temperature and around 673 K, where the samples were prepared by pulsed laser deposition at room temperature. The results of X-ray diffraction, transmittance spectroscopy and electron microscope observation indicate that both as-deposited film and heat treated film had amorphous structure with random hexagonal network of ZnO, where the latter included crystallized ZnO grains. The highest absolute value of Seebeck coefficient a was 135 μV/K at 643 K, where the electrical resistivity p was 1.01 x 10 - 4 Ωm and the power factor P was 1.79 x 10 - 4 W/mK 2 , and the a was almost the same as those of other ZnO compounds such as (ZnO) 5 In 2 O 3 and (Zn 1 - x Al x )O. The heat treatment dependence of the p and the a indicated the decrease of free electrons originated in amorphous and the transition to the quasi-stable phase of amorphous. It was suggested that the amorphous structure with variable range hopping conduction relates to the thermoelectric properties of a-ZnO thin film.