Nano-Fabrication on the Surface of Azobenzene-Containing Copolymers by Means of Optical Near Field around Microspheres

We demonstrate a photoinduced nanofabrication using azobenzene-containing copolymers that is applicable to dimensions beyond the diffraction limit. We present a nanometer-scaled patterning induced by optical near field around arrayed polystyrene microspheres. Various azocopolymers with different glass transition temperature (Tg) were synthesized and the depth of the nanofabrication depending on the Tg was examined. The dependency on the Tg was effected by the irradiated light power. We compared the deformation pattern on the surface with the calculated intensity distribution of the electric field around microsphere. This comparison and the polymer migration analysis show that the near-field gradient force induces the surface deformation.