Development of a tip enhanced near-field laser ablation system for the sub-micrometric analysis of solid samples

A near-field laser ablation system was developed for the analysis of inorganic solid samples in the nanometer resolution range. The instrument is based on the coupling of a nanosecond Nd:YAG laser with an atomic force microscope. The technique uses a tip enhancement effect obtained by the interaction of laser radiation with the conductive tip of the AFM maintained at a few nanometers above the sample surface. By applying this technique to conducting gold and semiconducting silicon samples, a lateral resolution of 100 nm was demonstrated. With a single laser pulse, craters of about 100 nm in diameter and a few nanometers in depth were obtained. A multi-parametric study was carried out in order to understand the effect of different experimental parameters (laser fluence, tip-to-sample distance, sample and tip nature) on the near-field laser ablation efficiency, crater dimensions and amount of ablated material. Numerical simulations of the localized heating with a home-made 3-D code presented a good explanation for the nanometer-sized crater diameters obtained in our experiments.