Re-distribution of oxygen at the interface between γ-Al₂O₃ and TiN

Area of Science:

• Materials Science
• Surface Science
• Solid-State Chemistry

Background:

• High-temperature annealing of atomic-layer deposited Al2O3 on TiN electrodes forms a stable γ-Al2O3 phase.
• Understanding interfacial chemistry is crucial for electronic device performance.

Purpose of the Study:

• To investigate the interfacial reactions and chemical states at the TiN/γ-Al2O3 interface.
• To characterize the influence of annealing and environmental effects on the interface.
• To correlate interfacial properties with electron barrier height.

Main Methods:

• Near edge X-ray absorption fine structure (NEXAFS)
• Conventional X-ray photoelectron spectroscopy (XPS)
• High-energy photoelectron spectroscopy
• Internal photoemission of electrons

Main Results:

• A ≈1-nm thick TiNxOy interlayer forms at the TiN/γ-Al2O3 interface due to oxygen scavenging.
• No TiO2 formation observed at the TiN/γ-Al2O3 interface.
• Environmental oxidation leads to TiO2/TiNxOy overlayers on the TiN electrode.
• Oxygen deficiency in γ-Al2O3 is observed, linked to polarization anisotropy.
• TiN electrode exhibits preferential orientation of 'stretched' octahedra.
• Anisotropy correlates with a ≈200 meV increase in electron barrier height at the O-deficient interface.

Conclusions:

• The TiNxOy interlayer formation is a key interfacial reaction.
• Oxygen deficiency and structural anisotropy significantly influence the electron barrier height.
• The findings provide insights into the interfacial engineering of TiN/Al2O3 based electronic devices.