Effect of dielectric stoichiometry and interface chemical state on band alignment between tantalum oxide and platinum

The tantalum oxide–platinum interface electronic properties determined by X-ray photoelectron spectroscopy are found to depend on the dielectric stoichiometry and platinum chemical state. We demonstrate the slow charging of the tantalum oxide in cases of Ta₂O₅/Pt and Ta₂O_5−y/Pt interfaces under the X-ray irradiation. This behavior is proposed to be related to the charge accumulation at oxygen vacancies induced traps. Based on the proposed methodology, we define the intrinsic conductive band offset (CBO) ∼1.3 eV (both for Ta₂O₅/Pt and Ta₂O_5−y/Pt) and CBO after the full saturation of the traps charging ∼0.5 eV, while the last one defines the energy position of charged traps below the bottom of conduction band. We demonstrate also the pining at the both Ta₂O₅/Pt and Ta₂O_5−y/Pt interfaces even in the "intrinsic" state, apparently induced by the presence of additional interfacial states. No shifts of Ta4f line and band alignment in over stoichiometric Ta₂O_5+x/Pt structure during X-ray irradiation, as well as the absence of pinning, resulting in increase of CBO up to 2.3 eV are found. This behavior is related to the PtO₂ interfacing layer formation at Ta₂O_5+x/Pt, blocking the charging of the surface states and associated dipole formation