Gas phase dynamics of laser -generated nanoparticle populations and its application to nanomaterials fabrication.

摘要

Naturally occurring materials often derive their outstanding properties from optimal anisotropic arrangements of nanoscale constituents. This requires a hierarchical organization of matter over several length scales, which is difficult to achieve in artificial materials made by conventional physical and chemical methods. This dissertation explores the combination of laser and aerosol processes as a novel approach to make thin film materials with a level of microscopic organization similar to that found in nature. Through a systematic investigation of the behavior of the gas-phase dynamics of nanoparticles generated by laser ablation of solid target materials in background gases and a study of the physical processes involved in gas-phase nanoparticle processing, a new instrument integrating a laser ablation source and an aerosol spectrometer was designed and implemented. Film deposition and nanoparticle deposition processes can be manipulated independently affording greater flexibility for materials fabrication than other laser methods.;The integrated laser-aerosol method is very flexible and can be used in the synthesis of a variety of materials. In this dissertation it is applied to the deposition of nanocomposite thin films comprising tetrahedral amorphous carbon (ta-C) with embedded metal nanoparticles. The controlled incorporation of metal nanoparticles enables the modulation of the electrical conductivity of ta-C over four orders of magnitude without significantly or adversely affecting its mechanical properties.