Thermal cycling and the optical and electrical characterization of self-assembled multilayer Nile Blue A-gold thin films

Some laser applications produce high power densities that can be dangerous to equipment and operators. We have fabricated thin-film coatings by using molecular electrostatic self-assembly to create a spectrally selective absorbing coating that is able to withstand thermal fluctuations from -20 (degree)C to 120 (degree)C. We made the thin-film coatings by alternating deposition of an organic dye and gold colloidal nanoparticles onto glass substrates. Nile Blue A perchlorate, with a maximum absorbance slightly above 632 nm, was chosen as the organic dye. Strong coupling between the dye molecules and the gold nanoparticles provides a redshift that increases as the filmʹs thickness is increased. The incorporation of the gold colloidal nanoparticles also decreases the resistivity of the film. The resistivity of the film was measured with a four-point probe and found to be ~10 (OMEGA)/cm for the two samples measured. Atomic-force microscopy was used to show that film thickness increased 2.4nm per bilayer. The optical properties of the film were measured at the end of every 5 thermal cycles from -20 (degree)C to 120 (degree)C, and negligible degradation was observed after 30 cycles.