Focused Laser Dewetting of Gold Nanofilms and Laser Induced Localized Physical Vapor Deposition

Focused laser spike (FLaSk) excitation has been repeatedly proven as a technique for the patterning of micro-to-nanoscale features locally by thermocapillary dewetting of thin films. Here we investigate the effect of overlapping laser exposures in the dewetting of ~15 nm gold films on borosilicate or quartz glass substrates. Due to the low viscosity and oxidation potential and high surface tension and vapor pressure of the gold melt, the FLaSk initiates the capillary and thermocapillary dewetting with the non-equilibrium vaporization simultaneously. The parameters of overlapping laser scans control the amount and temperature of the material heated, and thus we can tune the deposited film condition as well as the size and spacing of the nanoparticles deposited on the writing substrates or a positioned superstrate through a laser-induced localized physical vapor deposition (LILPVD) process. Additionally, if the substrate also melts during FLaSk, the liquid-on-liquid dewetting can broaden the patterning conditions by resisting the motion of the gold. Taking advantage of the ability to transfer a variety of nanoparticle morphologies to a target substrate, we have employed LILPVD to screen precursor morphologies for the growth of CdSe microstructures for tandem photovoltaic cells.