Instabilities during the formation of electroactive polymer thin films

Area of Science:

• Materials Science
• Polymer Science
• Thin Film Deposition

Background:

• Poly(n-vinyl carbazole) (PVK) is a widely studied polymer for electronic applications.
• Controlling the thin film structure is crucial for device performance.
• Spin-coating is a common method for depositing polymer thin films.

Purpose of the Study:

• To investigate how solvent properties influence the structure of PVK thin films.
• To understand the role of spin-coating dynamics in film formation.
• To determine whether thermodynamic equilibrium or process dynamics dominate film properties.

Main Methods:

• Thin films of PVK were prepared using spin-coating with five different solvents.
• Film properties such as surface roughness, structure, thickness, and density were analyzed.
• The influence of solvent characteristics (e.g., evaporation rate, water content) was examined.

Main Results:

• PVK thin films prepared by spin-coating are not in thermodynamic equilibrium.
• The presence of water in tetrahydrofuran (THF) induced dewetting during spin-coating.
• Solvents with high evaporation rates resulted in increased surface roughness due to Marangoni convection.

Conclusions:

• The surface roughness and structure of PVK thin films are primarily governed by the dynamics of the spin-coating process.
• Thermodynamic interactions between PVK and solvents play a secondary role in determining film morphology.
• Understanding spin-coating dynamics is essential for controlling PVK thin film properties.