Order-disorder transition in polycrystalline c60 films

Area of Science:

• Materials Science
• Solid State Physics
• Spectroscopy

Background:

• Fullerene C60 exhibits unique electronic and structural properties.
• Raman spectroscopy is a powerful tool for probing molecular vibrations and structural changes.
• The influence of environmental factors like oxygen on C60 properties is of significant interest.

Purpose of the Study:

• To investigate the low-temperature behavior of polycrystalline C60 films using high-resolution Raman spectroscopy.
• To understand the impact of temperature on the spectral characteristics of C60.
• To explore potential phase transitions and their relationship with molecular ordering and oxygen exposure.

Main Methods:

• Deposition of polycrystalline C60 films under ultrahigh-vacuum conditions.
• High-resolution Raman spectroscopy measurements at varying temperatures, particularly below 244 Kelvin.
• Comparative spectral analysis of C60 films exposed to air/oxygen versus oxygen-free conditions.

Main Results:

• At temperatures below 244 +/- 3 Kelvin, the Raman spectrum of C60 is a composite of two components.
• The relative intensity of these spectral components is dependent on temperature.
• The spectrum below 244 K differs from that observed at room temperature, with distinct characteristics for oxygen-exposed versus oxygen-free samples.

Conclusions:

• The observed temperature-dependent spectral changes suggest an order-disorder phase transition in C60 films.
• This transition may involve the percolation of C60 molecular clusters undergoing coherent Raman scattering.
• The findings highlight the sensitivity of C60's spectral properties to temperature and oxygen presence.