Strain-stabilized interfacial polarization tunes work function over 1 eV in RuO₂/TiO₂ heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• Interfacial polarization is a known phenomenon in semiconductors.
• Its role in metallic systems, particularly in modulating electronic properties, remains largely unexplored.

Purpose of the Study:

• To investigate the influence of interfacial polarization on the work function of metallic rutile ruthenium dioxide (RuO2).
• To explore the potential for controlling electronic properties in metals through interfacial engineering.

Main Methods:

• Epitaxial growth of RuO2/TiO2 heterostructures using hybrid molecular beam epitaxy.
• Direct visualization of polar ionic displacements near the interface using multislice electron ptychography.
• Measurement of work function modulation via Kelvin probe force microscopy.

Main Results:

• Demonstrated robust modulation of the RuO2 surface work function by over 1 eV.
• Observed significant work function changes with small variations in RuO2 film thickness (2-3 nm).
• Identified a critical thickness of approximately 4 nm for the transition from strained to relaxed films, correlating with polarization effects.

Conclusions:

• Interfacial polarization is a viable mechanism for tuning the electronic properties of metallic systems.
• This finding opens avenues for designing advanced electronic, catalytic, and quantum devices by controlling interfaces in polar metallic materials.