Nanofabrication by laser irradiation of polystyrene particle layers on silicon

Regular lattices of polystyrene (PS) microspheres formed by self-assembly processes were used for single-shot fabrication of large regular arrays of nanoparticles or nanobumps or nanoholes on Si surfaces. The morphologies of created nanofeatures were characterized by an atomic force microscope (AFM) and a scanning electron microscope (SEM). The near-field enhancements under the absorptive PS microsphere were studied and calculated. The ablation and thermal processes induced both by laser irradiation of the top surface of the PS microspheres and by the near-field enhancements underneath the microspheres were investigated. When the laser fluence was at a low value of 40mJcm^-2, periodic PS nanoparticle arrays were produced. With a laser fluence in the range of 100-170mJcm^-2, regular conical and circular-crater-shaped Si nanobump arrays were fabricated. When the laser fluence was high, up to 200mJcm^-2, hole arrays were formed in the Si substrate. The mechanisms of this nanofabrication are discussed. Experimental results are explained and are consistent with those of theoretical calculations.