Achieving superior band gap, refractive index and morphology in composite oxide thin film systems violating the Moss rule

Abstract

The interrelation between energy gap and high frequency refractive index in semiconductors and dielectrics is manifested by an inverse law which is popularly known as the Moss rule. This semi-empirical relationship is based on the fundamental principle that in a dielectric medium all energy levels are scaled down by a factor of the square of the dielectric constant. Such a rule is obeyed by most pure semiconductors and dielectrics with a few rare violations in composite materials which display several interesting parametric and microstructural evolutions. The present results are based on some specific oxide composite thin films involving Gd2O3/SiO2 and ZrO2/SiO2 codeposited systems that have displayed a superior refractive index and energy gaps violating the semi-empirical Moss rule. Also, morphological supremacy is also distinctly noticed in these composites. The novel microstructural and polarizability properties of such composite systems were probed through multi-mode atomic force microscopy and phase modulated spectroscopic ellipsometry using refractive index modelling, autocorrelation and height–height correlation functional analyses. These binary composite thin films have shown their potential as well as the possibility of meeting expectations in satisfying the challenging optical coating requirements of the deep ultraviolet spectral region.

Characterization of zirconia– and niobia–silica mixture coatings produced by ion-beam sputtering

“…For example, zirconia and niobia are widely used for the production of high refractive-index thin films, while SiO 2 is frequently used as a low-refractiveindex material. Some properties of zirconia-silica mixtures prepared with the IBS technique [7], ebeam deposition [20,21], and magnetron sputtering [22] were already investigated as well as those of niobia-silica prepared by e-beam deposition [23,24]. Nevertheless, the optical resistance of these mixtures produced by the IBS technique are not studied in detail at subpicosecond pulse durations.…”

Laser‐induced optical properties change in Sb10S40Se50 chalcogenide thin films: An investigation through FTIR and XPS measurements

“…The dispersion energy E d is associated with the changes in the structural order of the material and is related to the physical parameters of the material through the following empirical relationship [34] …”

Compositional evolution and surface-related phenomena effects in ZnS–SiO2 nanocomposite films

“…Considering the evaluated grain size (XRD study), this can be linked to the quantum size effect of ZnS nanoparticles embedded in the silica host matrix [13,44]. A similar shift in optical band gap has also been reported for SiO 2 -based composite [57]. The oscillation energy E o can be correlated with the estimated optical gap according to the empirical formula…”