fig3

Figure 3. Analysis of interfacial chemical composition and thermodynamic stability. (A) Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiles were obtained from HZO/MoN_x stacks with pure Mo, 05MoN, 52MoN, and 79MoN bottom electrodes. The profiles highlight the elemental distribution across the interfacial layer. The shaded areas are schematically highlighted as visual guides to denote the interfacial chemical transition zones, roughly encompassing the peak regions of the HfO₂- secondary ion signals. The red dashed circles mark the significant accumulation of oxygen-related fragments (MoO^- and MoO₂^-) within the IL for the Mo and 05MoN stacks, indicating severe oxidation. Conversely, the green dashed circles mark the peak of nitrogen-related fragments (HfN-) in the 52MoN and 79MoN stacks, indicating a nitride-rich interfacial region; (B) The evolution of Mo 3d X-ray photoelectron spectroscopy spectra was analyzed for as-deposited and annealed HZO/MoN_x stacks, showing the reduction of higher-valence oxides upon annealing. The red arrows indicate the binding-energy shift associated with reduction of MoO₃ to MoO₂ upon annealing; (C) Standard Gibbs free energies of formation (ΔGf°) per 1 mol of O₂ at 700 K for relevant oxides^[39,40]; (D) ΔGf° values per 1 mol of N₂ at 700 K for relevant nitrides^[39,43]; (E) Maximum secondary-ion intensities of MoO^-, MoO^2-, and HfN^- fragments were extracted from the ToF-SIMS profiles.