Microstructuring of polymers using light-controlled molecular migration processes

Christophe Hubert

CEA Saclay, DRT-LIST-DECS-SE2M-Groupe Composants Organiques
Saclay, France

Abstract: The possibility of manipulation and precise control of molecular order is a challenging prospect in the design and realization of devices for photonics applications. A new concept for microstructuration, based on photoinduced molecular migration in polymer films containing azobenzene dye was recently demonstrated. Irradiation with an interference pattern of polarised laser beams was observed to lead to substantial reversible mass-transport. The wavelength of the laser was choosen to be near the chromophores absorption band. We now show evidence that, under specific experimental conditions the interaction between a uniform laser beam from an argon laser and the polymer film induces hexagonal structures on the surface of the polymer. Such self-patterning process was observed to depend on several parameters such as the polarization of the laser beam, the angle of incidence, the wavelength, as well as the nature of the dye. The modulation amplitude of the polymer film can reach 100 nm for an initial film thickness of 300 nm, and the period of the structure is of the order of the wavelength. Understanding the fundamental mechanisms of such photoinduced self-patterning process should open a new route towards optical molecular control of materials microstructuring.