ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF LASER-NANOSPHERE INTERACTION FOR NANOSCALE SURFACE MODIFICATION

摘要

An investigation on the features created on a silicon substrate by the irradiation of nanospheres on the substrate surface with a pulsed laser is presented. Silica nanospheres of diameter on the order of laser wavelength are deposited on silicon substrate and irradiated with a pulsed Nd:YAG laser. As a result, nanofeatures are created on the surface by the melting and resolidification of silicon. The experiment is repeated for different laser wavelengths (532 nm, and 355 nm), sphere diameters (640 nm, and 1.76 μm) and laser energies, and the effect of each of these parameters on the features created are studied. An analytical model based on Mie Theory complements the results. The model includes all evanescent terms and does not rely on either far field or size-parameter approximations. The predicted intensity distributions on the substrate indicate a strong near field enhancement confined to a very small area (nanometer scale). The results correlate well with the feature geometries obtained in the experiment.