Creating Nanostructures with Lasers

Abstract

AbstractLasers represent an efficient and versatile tool to produce and to arrange in organized dispositions nanometer-sized particles, obtaining extended nanostructures with increasing degrees of complexity. In the first part of the chapter, the basic mechanisms of nanoparticle formation for nanosecond laser ablation in an ambient gas atmosphere and femtosecond ablation in vacuum are considered. In the former case, atomic or molecular clusters grow during the propagation through the ambient gas of the plasma plume resulting from target irradiation. Plume expansion is affected by laser wavelength and fluence, nature and pressure of the background gas, target to substrate distance. Cluster size and kinetic energy, together with the related distributions at landing onto the substrate depend on plasma dynamics and determine relevant differences of morphology and nanostructure of the growing film. Popular models for the propagation of an ablation plume through a gas at increasing pressure are recalled before deducing the average asymptotic size of particles nucleated in the plume, to be compared with available data from selected experiments. The synthesis of spatially uniform distributions of spherical metal particles with controlled size, size distribution, and number density, resulting in films with differentiated morphologies and optical properties is discussed.In recent years, increasing attention and efforts have been devoted to the controlled synthesis of nanostructured materials. The nanostructure plays a fundamental role in determining electronic, optical, magnetic, and mechanical material properties. It is in principle possible to engineer new functional systems by carefully tailoring their structure at the atomic and nanometer scales. One of the more exciting routes adopted to synthesize nanostructured thin films is the controlled assembling of clusters.Among different chemical and physical assembling techniques, laser processing plays an important role: laser ablation, pulsed laser deposition, laser micromachining, laser etching, and laser-assisted chemical vapor deposition are only some examples of recently introduced techniques that are reviewed with emphasis on the degree of control of the resulting artificial nanostructures.KeywordsPulse Laser DepositionDirect Simulation Monte CarloAblation PlumePhase ExplosionDrag ModelThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.