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Stainless-steel is ablated with femtosecond laser pulses at high repetition rate. A multi-pass, high spatial overlap laser scanning strategy is applied in order to cope with the requirements for large-scale machining of high aspect ratio structures. Topography of the processed surfaces is analyzed via Shear Force Microscopy scans, with the main aim to investigate morphology changes as a function of process parameters. Quantitative assessment of local height variations enables a detailed investigation of the produced features. Depending on the process parameters, in particular on laser fluence and repetition rate, a transition from small islands to large bumps is observed, explained in terms of feature coalescence.

Ripple-like nanostructure patterns are known to occur in ultrafast laser ablation with linearly polarized radiation. The observation of similar features at the bottom of grooves produced during laser ablation of stainless-steel with circular polarization is reported here. A comprehensive morphological analysis of the machined surfaces, carried out by electron and scanning probe microscopes, reveals a marked dependence of feature shape on process parameters, in particular on the scanning velocity of the laser spot. Such a dependence is interpreted based on the occurrence of an inclined surface during the ablation and on the consequent differential absorption of s- and p-polarized components of the laser radiation by stainless-steel. The resulting anisotropy of the absorbed energy mimics irradiation with elliptical polarization that can drive formation of ripple-like, elongated nanostructures.

In this article we will present architecture, properties and application of a novel scanning probe microscopy (SPM) piezoresistive cantilever with thermal deflection actuator. This microprobe with an integrated planar microtip is utilized in shear-force microscopy (ShFM) in which the cantilever microtip vibrates parallel to the surface. We will describe the calibration procedure of sensitivity of cantilever piezoresistive deflection detection, thermal actuation and experimental setup of the developed measurement system. We will also present results of topography measurements of highly oriented pyrolytic graphite (HOPG) and Hafnia alvei bacteria culture surface using developed ShFM system.