Pulsed-laser-induced melting and solidification of aluminum thin films

Pulsed-laser-irradiation of thin semiconductor films has been actively pursued in recent years for investigating various phase transformation scenarios that can take place under far-from equilibrium conditions, as well as to obtain polycrystalline silicon thin films for high-performance thin film transistor devices. In contrast, not much has been accomplished concerning pulsed-laser-induced melting and solidification of thin metallic films. Given that thin metallic films are also of technological relevance, and further that they represent potentially simple and ideal systems for investigating highly metastable transformations, it may be worthwhile to systematically look into pulsed-laser-induced melting and solidification of metallic thin films.; This dissertation corresponds to an explicit attempt to address such an opportunity; this is accomplished by investigating excimer-laser-induced melting and solidification of Al thin films. Specifically, it consists of two apparently distinct yet synergistically coupled projects: (1) a systematic investigation of the details of phase transformation scenarios that are encountered in the irradiated films, as well as (2) the development of irradiation techniques to produce microstructurally engineered polycrystalline Al films.; We have found that the overall phase transformation scenarios that are encountered in single-pulse-irradiated Al thin films are primarily equivalent to what we have previously observed in semiconductor materials. Nevertheless, the microstructural analyses of the irradiated Al films reveal some distinct and noteworthy features that include (1) the presence of heavily (111) textured Al grains upon complete melting of the films and (2) the surface morphology of the laterally solidified Al grains, wherein strong grain boundary grooving is observed. The systematic experiments and subsequent analysis lead us to conclude that the (111) textured Al grains are formed through fully stochastic (i.e., temporally as well as spatially random) nucleation of solids via the heterogeneous mechanism. This conclusion is noteworthy as this may correspond to the very first experimental observation that directly supports the previously proposed and discussed theory of oriented heterogeneous nucleation of solids in supercooled liquids.; We have also succeeded in developing two specific crystallization schemes for producing microstructurally optimized polycrystalline Al films. One approach accomplishes this by implementing a pulsed-laser-irradiation-based lateral solidification method, referred to as Sequential Lateral Solidification (SLS); this process was previously invented in order to crystallize thin Si films. Alternatively, microstructure-engineered polycrystalline Al films with desired characteristics are obtained via a newly developed single-pulse-irradiation technique, which we have named the Nucleation-Engineered Solidification (NES) method. (Abstract shortened by UMI.)...