Terahertz conductivity of high-quality indium films deposited using a substrate cooling method

High-quality indium thin films were fabricated by substrate cooling method during the metal deposition. The cooling effect reduced the threshold thickness for insulator-to-metal transition, which originates from the interconnections between the indium nano-islands. The complex conductivities of the films were measured by terahertz time-domain spectroscopy. We showed that the conductivity of the indium films prepared by substrate cooling were ∼10 times higher than that deposited at room temperature, even though thickness of the former was lower than that of the latter film. Our results suggest that substrate cooling is promising for the applications of metal thin films and contacts.