RESUMEN
Films containing a layer of Ag nanoparticles embedded in silicon dioxide were produced by RF magnetron sputtering. Optical transmittance measurements at several angles of incidence (from normal to 75°) revealed two surface plasmon resonance (SPR) peaks, which depend on electric field direction: one in the ultraviolet and another red-shifted from the dilute Ag/SiO2 system resonance at 410 nm. In order to investigate the origin of this anisotropic behavior, the structural properties were determined by transmission electron microscopy, revealing the bidimensional plane distribution of Ag nanoparticles with nearly spherical shape as well as the filling factor of metal in the composite. A simple model linked to these experimental parameters allowed description of the most relevant features of the SPR positions, which, depending on the field direction, were distinctly affected by the coupling of oscillations between close nanoparticles, as described by a modified Drude-Lorentz dielectric function introduced into the Maxwell-Garnett relation. This approach allowed prediction of the resonance for light at 75° incidence from the SPR position for light at normal incidence, in good agreement with experimental observation.
RESUMEN
Normal incidence transmittance and reflectance spectra of sputtered nanocomposite monolayer films of Ag in SiO2, buried and unburied, showed significant redshifted plasmon resonances from 410 to 455 nm, which could be well interpreted with a simple model that starts from the Maxwell Garnett theory and the Kreibig extension of the Drude-Lorentz equation, but with a further extension related to the dipolar interaction between the metal particles distributed on a surface.
RESUMEN
A brief overview of optical monitoring for vacuum and wet-bench film-deposition processes is presented. Interferometric and polarimetric measurements are combined with regard to simultaneous monitoring of refractive index and physical thickness in real time. Monitoring stability and accuracy are verified during dip coating with a transparent oil standard. This double optical technique is applied to dip coating with a multicomponent zirconyl chloride aqueous solution, whose resulting temporal refractive-index and physical-thickness curves indicate good reproducibility as well as significant sensitivity to changes of film-flow properties during the dip-coating process.
RESUMEN
Real-time interferometric monitoring of the dip coating process is applied to the study of properties of flowing liquids. Nonvolatile Newtonian oils are considered, allowing validity of a simple model after the steady state is reached where film physical thickness depends on time as t(-1/2). Measurement of two distinct mineral oil standards, under several withdrawing speeds, resulted in kinematic viscosities of 1.17+/-0.03 and 9.9+/-0.2 S (1S = 1 cm2/s). Agreement of these results with nominal values from the manufacturer suggests that interferometric monitoring of dip coating may become a valuable method for accurate, contactless viscometry of liquid films. Advantages and present limitations are discussed.
RESUMEN
Dip-coated films, which are widely used in the coating industry, are usually measured by capacitive methods with micrometric precision. For the first time to our knowledge, we have applied an interferometric determination of the evolution of thickness in real time to nonvolatile Newtonian mineral oils with several viscosities and distinct dip withdrawing speeds. The evolution of film thickness during the process depends on time as t(-1/2), in accordance with a simple model. Comparison with measured results with an uncertainty of +/- 0.007 microm) showed good agreement after the initial steps of the process had been completed.