Raman Scattering of Solid and Liquid Clusters and Ultrathin Films

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Enhanced Raman scattering methods will be used for in situ ultra- high vacuum studies of clusters and ultra-thin films deposited on surfaces. Information about the phonon states and their changes with cluster size and temperature will be obtained. Emphasis will be places on the semiconducting and semimetallic group IV (C and Sn) and V (Bi and Sb) elements in amorphous or nanocrystalline states. Raman scattering will also be applied to liquid clusters from this group to obtain dynamical information on the phase transformations from the solid to liquid state. Sputtering and laser assisted deposition methods will be employed for cluster and ultra-thin film growth. Photoemission and high resolution electron energy loss methods will provide complementary information on changes in electronic and vibrational states and the role of atomic hydrogen bonding on surfaces. %%% This research will focus on both near surface and bulk properties of ulrathin and thin films with different nanostructures. Emphasis will be placed on studies of semiconductor or semimetal cluster structures in which both the relatively small number of atoms and the large surface to volume ratio allow modified material properties to be achieved. Both solid as well as liquid state cluster properties will be explored. The preparation of these materials will employ a diverse range of ultrahigh vacuum deposition methods, including magnetron sputtering, evaporation and laser assisted deposition. The physical properties and characterization of these materials will employ a range of in situ ultrahigh vacuum spectroscopic methods. This will provide information on the electronic state and vibrational dynamics of disordered amorphous and nanocrystalline solids and will explore the role of bonding and structural disorder changes in the processing of ultrathin films. Additional ex situ transmission electron microscopy studies of cluster size distributions will be obtained and related to synthesis methods. Laser assisted deposition of amorphous carbon and other diamond-like materials will involve university-industry collaborations.