Enhancing Optical and Electronic Properties of Indium-doped ZnO Thin Films through Substrate Temperature Control

Abstract

Indium (In)-doped ZnO thin films were deposited on glass substrates via radio frequency reactive magnetron sputtering at substrate temperature at 180, 200, 225, and 250°C. X-ray diffraction data shows In-doped ZnO samples displayed the hexagonal wurtzite structure typical of ZnO. Atomic force microscopy indicates the surface roughness enhance when increasing the growth temperatures. Ultraviolet-visible transmission spectroscopy of In-doped ZnO thin films exhibited over 80% transmittance in the visible region. Additionally, the optical bandgap ranges from 3.23 to 3.41 eV and tends to widen with increasing the growth temperature. The Hall effect measurements reveal that a carrier concentration exceeding 10²¹ cm⁻³ and a resistivity of approximately 10⁻⁴ Ω cm. Furthermore, the Seebeck coefficient of the In-doped ZnO thin films ranges from 23.15 to 32.7 µV K⁻¹, with a power factor between 3.23 and 247.02 µW m⁻¹ K⁻². Our results highlight the important role of substrate temperature in controlling the morphological, structural, optical, electrical, and thermoelectrical characteristics of In-doped ZnO thin films, which may lead to the material’s optimization for modern technological applications.