Electron Beam Patterning of Polymerizable Ionic Liquid Films for Application in Photonics.

Area of Science:

• Materials Science
• Nanotechnology
• Photonics

Background:

• Traditional fabrication of planar photonic components uses spin-coating of polymer films, which involves volatile solvents posing environmental and health risks.
• There is a need for greener, safer, and efficient methods for microfabrication.

Purpose of the Study:

• To investigate room-temperature ionic liquids (RTILs) with polymerizable allyl groups as a solvent-free alternative for electron-beam patterning.
• To compare the microfabrication quality using different RTILs and analyze the polymerization mechanism and resulting microstructure properties.

Main Methods:

• Electron beam patterning of thin films of three different polymerizable RTILs ([Allmim][Cl], [Allmim][NTf2], [Allmmim][NTf2]) in vacuum.
• Analysis of microstructure shape distortion, viscosity, surface tension, and polymerization chemistry using Fourier-transform infrared spectroscopy (FTIR).

Main Results:

• Solvent-free planar polymer microstructures were successfully fabricated using electron beam patterning of RTILs.
• More viscous RTILs ([Allmim][Cl]) showed less shape distortion during polymerization compared to less viscous ones ([Allmim][NTf2], [Allmmim][NTf2]).
• Free radical polymerization is identified as the likely mechanism, evidenced by the disappearance of C=C bonds via FTIR.

Conclusions:

• Polymerizable RTILs are a viable, eco-friendly material for solvent-free microfabrication of planar structures.
• Viscosity and thermocapillary effects influence microstructure fidelity during electron beam processing.
• The resulting polymerized microstructures exhibit good optical properties, making them suitable for planar photonic applications.