Comparative Study of the Surface Nanostructure Formation on Different Surfaces Generated by Low Number of fs Laser Pulses

Abstract

Despite the early observation of laser induced periodic surface structures, the mechanism responsible for their formation is still in the focus of an intense debate. To deduce the processes dominating the formation, we investigated the surface structuring of Si, GaAs and V surfaces by femtosecond laser pulses in identical conditions. All material surfaces showed the traces of melting at low pulse numbers, and in all cases ripples were observed with periods of several hundreds of nanometers. The orientation of the ripples appearing already in case of the smallest pulse number was perpendicular to the polarization of laser light. In case of Si, a second stripe system developed on the surface at higher pulse number. The orientation of this structure was parallel to the polarization of laser light, and had a period similar to the original stripe system. The formation of the observed structure is discussed in the frame of capillary waves excited by laterally periodic fluence and melting. The periodic excitation is attributed to the interference of the incoming and scattered laser light.