Effects of atomic scale roughness at metal/insulator interfaces on metal work function

Area of Science:

• Materials Science
• Computational Chemistry
• Condensed Matter Physics

Background:

• Predicting the electronic properties of metal/insulator interfaces is crucial for device applications.
• Density functional theory (DFT) is a primary tool for such investigations.
• Accurate modeling of van der Waals (vdW) interactions is essential for interfacial phenomena.

Purpose of the Study:

• To evaluate various vdW-corrected DFT methods for interface structure prediction.
• To assess the accuracy of these methods in calculating the work function shift of Ag(001) upon deposition of LiF, MgO, and NiO films.
• To identify limitations of current vdW-DFT functionals for metal/insulator interfaces.

Main Methods:

• Utilized density functional theory (DFT) with different van der Waals (vdW) corrections.
• Simulated perfect interfaces between Ag(001) and LiF(001), MgO(001), NiO(001) films.
• Calculated interface structures and work function shifts.

Main Results:

• Including vdW interactions is critical for accurate interface structures and work function shift predictions.
• Work function shifts are highly sensitive to subtle interface geometry changes.
• Current vdW-DFT functionals exhibit insufficient accuracy (within 0.2 eV) for predicting work function shifts.
• Most tested vdW functionals are not optimal for metal/insulator interfaces.

Conclusions:

• vdW interactions significantly influence metal/insulator interface properties.
• Existing vdW-DFT methods require improvement for accurate work function shift predictions.
• Lack of experimental interface geometry data hinders the development and calibration of new DFT functionals.