Synthesis, Composition, and Electronic Structure of Cr−Si−N Thin Films Formed by Reactive Ion Beam Mixing of Cr/Si Interfaces

Abstract

Cr−Si−N thin films have been synthesized by 3 keV N2+ reactive ion beam mixing (IBM) of Cr/Si interfaces. The kinetics of growth, composition, and electronic structure of the films formed have been analyzed using X-ray photoelectron spectroscopy, angle-resolved X-ray photoelectron spectroscopy (ARXPS), ultraviolet photoelectron spectroscopy, factor analysis, and Monte Carlo TRIDYN simulations. ARXPS results show that the composition of the films formed by reactive IBM is rather uniform in the near-surface region. The comparison of experimental results with those obtained from TRIDYN, which uses pure ballistic mechanisms, suggests that the processes driven by residual defects are the rate-controlling mechanisms during the reactive IBM of Cr/Si interfaces. The reactive IBM kinetic is characterized by two stages: below ∼3 × 1016 ions/cm2, a strong decrease of the Cr concentration along with a fast nitrogen incorporation is observed. This behavior can be explained mainly by Cr sputtering and nitrogen implantation. During this first stage, the formation of chromiun nitride and a small Si incorporation in the near-surface region are also observed, suggesting the formation of a CrNx/SiNx nanocomposite film. For ion doses above ∼3 × 1016 ions/cm2, the Cr/Si ratio can be varied in a broad range with nearly constant nitrogen concentration, as a consequence of sputtering, nitruration, and strong intermixing effects taking place simultaneously. Furthermore, during this second stage, chromium nitride is tranformed into a ternary (Cr−Si)N compound due to the strong Si incorporation in the near-surface region.