Charge-transfer interface of insulating metal-organic frameworks with metallic conduction

Area of Science:

• Materials Science
• Condensed Matter Physics
• Chemistry

Background:

• Hetero-structured thin films are crucial for exploring interfacial phenomena.
• Metallic conduction at interfaces is well-known in oxides but elusive in metal-organic frameworks (MOFs).
• MOFs, crystalline materials of metal centers and organic linkers, are typically electrical insulators due to poor orbital overlap.

Purpose of the Study:

• To fabricate and investigate interfacial metallic conduction in hetero-structured MOF thin films.
• To understand the fundamental mechanisms behind this observed electronic behavior.
• To explore the potential of MOFs in novel electronic applications.

Main Methods:

• Fabrication of hetero-structured thin films using a layer-by-layer method, combining a Mott and a band insulating MOF.
• Electrical transport measurements to characterize the conductivity across the thin film interface.
• First-principles density functional theory (DFT) calculations, including Bader charge analysis, to elucidate the electronic structure and charge distribution.

Main Results:

• Successful fabrication of hetero-structured MOF thin films.
• Experimental evidence of interfacial metallic conduction across the fabricated thin films.
• Theoretical calculations confirmed significant charge accumulation and percolation at the MOF-MOF interface, explaining the metallic behavior.

Conclusions:

• Interfacial metallic conduction can be achieved in hetero-structured MOF thin films.
• Charge accumulation and percolation at the interface are key mechanisms for this phenomenon.
• This work paves the way for designing other MOF-based hetero-structures with tunable electronic properties.