Metal- and oxide-related hydrogen-induced dipoles at the Pt/HfO2 interface

Such technologically abundant agent as hydrogen has a strong effect on the metal/oxide interface energy barrier. Internal photoemission analysis of electron barrier height variations at Pt/HfO2 interfaces caused by annealing in hydrogen reveals the formation of a significant (0.4eV) electrostatic dipole layer. The orientation of the H-induced dipole appears to be sensitive to the growth conditions and treatments, e.g., Hf precursor used in the atomic layer deposition (ALD) process: In the case of the HfCl4 precursor, annealing in H2 leads to barrier lowering, whereas the barrier becomes higher in samples grown by using tetrakis(dimethylamido)hafnium. These findings indicate that hydrogen may form dipoles of opposite orientation through two different mechanisms: The positive dipole is caused by H interaction with the metal surface, which can also be found at interfaces of Pt with other oxides such as SiO2 and Al2O3. By contrast, the sensitivity of the negative dipole formation to the HfO2 ALD chemistry suggests it to be related to a negatively charged bonded state of hydrogen in the near-interface oxide. Moreover, the formation of positive dipole is also observed after high temperature anneal in nitrogen suggesting the contribution of additional mechanisms of dipole formation. Display Omitted Hydrogen-related dipole at Pt/HfO2 interface is formed through competing mechanisms.Opposite dipole orientation for two oxides grown by using different ALD precursors.Additional mechanism of dipole formation due to annealing conditions