(108a) Fluid-Phase Self-Organization In Nanoscopic Metal Films Under Pulsed Laser Irradiation

Light waves, when directed to the interface between a metal and a dielectric are capable of a resonant interaction with the mobile electrons present at the surface of the metal, giving rise to surface plasmons, i.e. density waves of electrons that propagate along the interface [1]. Metallic nanoparticles on or embedded in dielectric materials offer great promise in ?shepherding? light waves along nanoscale interconnects for ultrafast information processing. Similarly, such nanocomposites offer much potential in designing materials with enhanced light absorption [2]. For instance, the optical response of a multi-metal nanocomposite material may be tailored to the solar spectrum via the manipulation of processing parameters such as volume fraction, particle size, and particle nanostructure.

Laser-induced dewetting and self-organization in nanoscopic (1- 10 nm) metals films supported on dielectric substrates is a robust technique for the synthesis of optical/solar nanocomposites [3-7]. Fluid phase instabilities, which arise as consequences of competing mechanisms including laser-film interactions, intermolecular forces, thermo-capillary effects and Rayleigh breakup, initiate and foster the self-organization process [3-6]. In this presentation, we will briefly discuss the effect of laser pulse properties, film thickness and materials parameters on the melt threshold and liquid phase life time of the metal. Subsequently, experimental observations of fluid phase instabilities and pattern formation that cause the self-organization of the thin film into nanowires or nanoparticles will be discussed. A theoretical framework for understanding the length scale selection as function of film height and thermo-physical process variables will be discussed. The predictions of a linear stability analysis based on thin film equation for the fastest growing mode will be compared with experimental observations of dominant length scales. Nonlinear film evolution will be discussed using results from numerical simulations and experiments.

1. H. A. Atwater, The Promise of Plasmonics, Scientific American, April 2007.

2. J. Trice, D.G. Thomas, C. Favazza, R. Sureshkumar & R. Kalyanaraman, Investigation of pulsed laser induced dewetting in nanoscopic metal films, in press, Phys. Rev. B. (2007) http://arxiv.org/abs/cond-mat/0609182

3. C. Favazza, R. Kalyanaraman & R. Sureshkumar, Robust nanopatterning by laser-induced dewetting of metal nanofilms, Nanotechnology, 17, 4429-34 (2006).

4. C. Favazza, J. Trice, H. Krishna, R. Kalyanaraman & R. Sureshkumar, Laser induced short and long range ordering of Co nanoparticles on SiO2, Appl. Phys. Lett. 88, 153118 (2006).

5. C. Favazaa, J. Trice, H. Garcia, R. Kalyanaraman & R. Sureshkumar, Nanoparticle ordering by dewetting of Co on SiO2, J. Electronic Materials, 35, 1618-20 (2006).

6. C. Favazza, J. Trice, R. Kalyanaraman and R. Sureshkumar, Self-organized metal nanostructures through laser driven thermocapillary convection, under review, http://arxiv.org/abs/0704.1179