Thickness-dependent carrier transport of PdSe₂films grown by plasma-assisted metal selenization

Atomically thin narrow-bandgap layered PdSe₂has attracted much attention due to its rich and unique electrical properties. For silicon-compatible device integration, direct wafer-scale preparation of high-quality PdSe₂thin film on a silicon substrate is highly desired. Here, we present the low-temperature synthesis of large-area polycrystalline PdSe₂films grown on SiO₂/Si substrates by plasma-assisted metal selenization and investigate their charge carrier transport behaviors. Raman analysis, depth-dependent x-ray photoelectron spectroscopy, and cross-sectional transmission electron microscopy were used to reveal the selenization process. The results indicate a structural evolution from initial Pd to intermediate PdSe_2-phase and eventually to PdSe₂. The field-effect transistors fabricated from these ultrathin PdSe₂films exhibit strong thickness-dependent transport behaviors. For thinner films (4.5 nm), a record high on/off ratio of 10⁴was obtained. While for thick ones (11 nm), the maximum hole mobility is about 0.93 cm²V^-1S^-1, which is the record high value ever reported for polycrystalline films. These findings suggest that our low-temperature-metal-selenized PdSe₂films have high quality and show great potential for applications in electrical devices.