Angle effect in laser nanopatterning with particle-mask

Parallel nanostructuring of substrate surface with particle-mask is a promising technology that may significantly improve the patterning speed under single laser pulse irradiation. In this paper, the influence of the incidence wave angle on the pattern structures is investigated. Polystyrene spherical particles were deposited on the surface in a monolayer form by self-assembly. The sample was then irradiated with 248 nm KrF laser at different incidence angles alpha. It is found that nanostructures can be formed at different positions with different incidence angles. Both round-shape and comet-shape nanostructures can be produced. By varying the incidence angles, the depth of the nanostructures can also be controlled. To explain the different nanostructures produced at different angles, the intensity field distributions under the particle were calculated according to an exact model for light scattering by a sphere on the substrate (P. A. Bobbert and J. Vlieger, Physica A 137A, 209 1986). The main equation in the original model was reformed for the ease of numerical simulation. A method was proposed to calculate the total electric and magnetic field as an extension to the model. The theoretical results are in good agreement with the experimental results. (C) 2004 American Institute of Physics.