Influence of Surface Adsorption on the Electrical Transport Properties of Ultrathin Indium Tin Oxide Films

Abstract

We systematically investigated the temperature-dependent behaviors of the resistivities ρ and carrier concentrations n of a series of ultrathin indium tin oxide (ITO) films with thickness t ranging from ∼5.3 to ∼35.0 nm grown on yttrium-stabilized ZrO2 substrates. For the t ≳ 17.5 nm films, the resistivity versus temperature can be described by the Bloch–Grüneisen formula, and the carrier concentration almost retains constant over the whole measured temperature range. For the t ≃ 5.3 nm (7.0 nm) film, the carrier concentration increases with increasing temperature above ∼300 K, and the resistivity initially increases with increasing temperature and then decreases with further increasing temperature above ∼330 K (∼355 K). By comparison of the transport properties of ITO films depositing on different substrates and exposing the films on different atmospheres, it is found that the enhancement of carrier concentration and reduction of resistivity at high temperature regime originate from the dissociative adsorption of water vapor on the surface of the ITO films.