Numerical study of The Remittances of Axially Excited Chiral Sculptured Zirconia Thin Films

The transmission and reflection spectra from a right-handed chiral sculptured zirconia thin film are calculated using the coupled wave theory and the Bruggeman homogenization formalism in conjunction with the experimental data for the relative dielectric constant of zirconia thin film. The dielectric dispersion function effect on these spectra appeared in wavelengths shorter than the Bragg wavelength. In wavelengths larger than the Bragg wavelength, the dispersion of the dielectric function can be ignored. The results achieved in this work are consistent with the experimental data (Wu et al. (2000)). A shift towards shorter wavelengths is observed for the Bragg peak with increasing the void fraction, which is in agreement with the theoretical work of Lakhtakia (2000). Sorge et al. (2006) also found this effect in their experimental results on TiO2 chiral thin films, while they also found that unlike our results the intensity of the reflectance of the Bragg peak decreases with increasing the void fraction. This difference between our theoretical work and Sorge et al. (2006) experimental work can be related to the structural difference between idealized theoretical model for chiral films and that obtained in experimental work. In the latter, as Sorge et al. (2006) have pointed out the experimental films exhibit a large amount of scattering due to the highly complex and non-ideal structure that the individual chiral elements exhibit.Comment: 19 pages, 7 figure

Molecular Dynamic Simulation Model for the Growth of Thin Films in The Structure Zone Model

A two dimensional molecular dynamic (atomistic) simulation model was used to investigate the relationship between the nano-structure and the deposition parameters; namely, substrate temperature, deposition rate, angle of incidence, surface roughness. Qualitative agreements with the predictions of the structure zone model (SZM) and the theoretical results of Srolovitze and coworkers (1988), as well as expectations through changes in the activated processes during film growth due to changes in deposition parameters (Grovenor and coworkers (1984)) are obtained. It is shown that by enhancing the atomic mobility (i.e., increasing the substrate temperature or/and lowering the deposition rate) films of higher density with fewer voids are produced. By increasing the deposition angle, the nano-structure of the film changes from a dense film with few voids, to a nano-structure with columns/boundless inclined with the same angle ( β ) towards the incidence atoms with elongated voids. The angle β increases with increasing the deposition angle (α ), and in agreement with the tangent rule (Dirks and Leamy (1977)). The angle of bundles (or the angle of the formation of the voids between atomic bundles), and columnar structure are caused by shadowing effects. Results showed that β decreases slowly with increasing surface mobility (i.e., increasing the substrate temperature or/and reducing the deposition rate). In general, the model provides almost all predicted results and agrees well with observation