Inelastic light scattering: a multiscale characterization approach to vibrational, structural and thermo-mechanical properties of nanostructured materials A. Li Bassi * , C.E. Bottani, C. Casari, M. Beghi Micro- and Nanostructured Materials Laboratory, Nuclear Engineering Department, Politecnico di Milano, Istituto Nazionale per la Fisica della Materia (INFM), Via Ponzio 34/3, 20133 Milano, Italy Abstract Inelastic light scattering is a powerful technique for the characterization of nanostructured materials, at different length scales. Raman scattering is a well established tool for materials characterization (structure, bonding and composition), through the measurement of vibrational properties. Due to phonon confinement, the Raman spectra of nanoparticles and nanostructured materials are substantially different from the spectra of the corresponding bulk, and provide useful information relative to the size and the dynamical behavior of the building blocks. In situ measurements permit the investigation of phenomena such as cluster deposition, film growth, thermal and chemical stability of nanostructures. Brillouin spectroscopy measures acoustic phonons and elastic properties of thin films and bulk materials at a mesocopic scale (hundreds of nanometers). The observation of acoustic damping and localization in nanostructured materials gives access to information such as interaction between nanoscale constituents, phase transitions, self-similar properties and meso-structure dynamical behavior. We provide a wide range of examples: characterization of the elastic properties of cluster-assembled films and ultrathin protective layers; in situ Raman spectroscopy of metastable linear carbon aggregates (carbynes) produced by cluster beams; measurement of acoustic modes in carbon nanotubes; detection of surface melting of metallic nanoparticles, by detection of confined vibrational modes. # 2003 Elsevier B.V. All rights reserved. PACS: 78.30.j; 78.35.þc; 63.22.þm; 61.46.þw Keywords: Inelastic light scattering; Raman spectroscopy; Brillouin spectroscopy; Low-dimensional structures; Nanostructured materials; Cluster-assembled materials 1. Introduction The synthesis of nanostructures and nanostructured materials is gaining enormous relevance in view of the peculiar properties characterizing matter when confined on a small scale. This research field is highly multidisciplinary and involves physics, chemistry, engineering, biology. Both fundamental science and practical applications can benefit from the compre- hension of nanostructure properties and, above all, of the way of handling and tailoring their properties, e.g. by controlling the deposition or synthesis of materials. To this purpose, nanoscience and nanotech- nology need more and more sophisticated character- ization tools, able to investigate structural, electronic, Applied Surface Science 226 (2004) 271–281 * Corresponding author. Tel.: þ39-02-2399-6331; fax: þ39-02-2399-6309. E-mail address: andrea.libassi@polimi.it (A. Li Bassi). URL: http://nanolab.cesnef.polimi.it. 0169-4332/$ – see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2003.11.041