Characterization of plumes produced during ultrashort laser ablation of metals and semiconductors

The characterization of a plasma plume is a key issue in laser ablation and deposition studies. Combined diagnostic measurements by Optical Emission Spectroscopy (OES), ion time-of-flight (TOF) and Atomic Force Microscopy (AFM) have been used to study the dynamics and composition of laser ablation plume produced during ultrashort laser irradiation of metals and semiconductors, in vacuum. Our results show that, in the laser intensity range of 10(12)-10(13) W/cm(2), the process of matter removal results in a plasma plume which is mainly composed of two different populations: atoms and nanoparticles. The nanoparticles dynamics during expansion has been analyzed through their structureless continuum optical emission, while atomic species have been identified by their characteristic emission lines. Atomic force microscopy analysis of the material deposited at room temperature has allowed the characterization of the nanoparticles size distribution. In the case of silicon, the presence of a fast ion component emitted non-thermally from the sample surface as a result of the supercritical state induced by the intense ultrashort laser pulse irradiation has been also observed.