Formation of fullerides and fullerene-based heterostructures

Area of Science:

• Materials Science
• Solid State Physics
• Chemistry

Background:

• Fullerenes, specifically C(60), are carbon allotropes with unique electronic properties.
• Potassium fullerides are compounds formed by the reaction of potassium with C(60).
• Understanding the phase behavior and stability of potassium fullerides is crucial for their applications.

Purpose of the Study:

• To investigate the formation and stability of different potassium fulleride phases.
• To examine the interfaces between C(60) and potassium fulleride phases.
• To determine the conditions under which phase separation and migration occur.

Main Methods:

• Thin C(60) films were prepared under ultrahigh vacuum conditions.
• Potassium was incorporated into the C(60) films to form different stoichiometries.
• Heterostructures of C(60) with K(3)C(60) and K(6)C(60) were analyzed for stability.

Main Results:

• Two distinct potassium fulleride phases were identified: metallic K(3)C(60) and nonmetallic K(6)C(60).
• Phase separation was observed for intermediate potassium-to-C(60) ratios.
• The C(60)-K(3)C(60) heterostructure exhibited stability against potassium migration.
• The C(60)-K(6)C(60) interface was found to be unstable, leading to the formation of K(3)C(60).

Conclusions:

• The stability of potassium fulleride phases depends on their stoichiometry and interfacial interactions.
• K(3)C(60) is a stable phase, whereas K(6)C(60) can transform into K(3)C(60) at interfaces with C(60).
• These findings provide insights into the phase diagram and structural properties of potassium-C(60) systems.