Abstract

Ultrafast laser assisted atom probe tomography (LA-APT) is a powerful nano analysing instrument that provides 3D maps of the chemical distribution in small volumes of either metallic and semiconducting materials or even high-K oxides with a sub nanometre spatial resolution [1]. In the atom probe tomography (APT), surface atoms are emitted from a tip in the form of ions by the combined action of an electrostatic (dc) field and of a laser pulse that triggers the emission. In laser assisted APT, the interaction of the laser beam with the tip increases its temperature and hence allows the evaporation of surface atoms. Several publications have dealt with modelling the laser heating of the illuminated tip in order to evaluate its maximum expansion [2] or the ions field emission efficiency in APT. Moreover, the absorption dependence on the laser polarization has been calculated, for a planar surface, an infinite cylinder and nanometric objects.[3] In the case of tips, however, the polarization effect was only investigated experimentally by Lee et al.,[4] and the results showed a continuous increase in the absorption when changing the polarization of the incident light from the tip axial direction to the transverse one. However, we demonstrate in this paper that the polarization dependence of the absorption of a subwavelength tip is strongly wavelength dependent and that a longitudinal polarized excitation can lead to higher absorption than a transverse one[5].

© 2011 IEEE