Substoichiometric zirconia thin films prepared by reactive sputtering of metallic zirconium using a direct current ion beam source

Abstract

An ultra-high-vacuum-compatible direct current ion beam sputter source is used to deposit strongly defective zirconium dioxide thin films by operation in high vacuum with different oxygen and hydrogen partial pressures. It is shown that the target drain current can be used as a quantity to measure the deposition rate and the film thickness (via integration over time). The latter has a linear relation to the integrated drain current, enabling the simple prediction of the thicknesses after calibration, enabling a large range of possible thicknesses (from small sub-monolayer islands to more than 50 nm). Furthermore, the defective nature of the films is shown when sputter-depositing onto copper and silicon substrates in different low oxygen (and hydrogen) pressures. When sputtering in hydrogen, traces of metallic Zr appear, which are much more pronounced for the deposition on Si, owing to a possible reactive sputtering mechanism that involves a reaction with oxygen that is adsorbed on the substrate. In the end, we show calculations that demonstrate that, with simple modifications, multiple sputter source configurations for different purposes are possible, leading to different deposition rates.