86 research outputs found
Fabrication of graded helical square tower-like Mn sculptured thin films and investigation of their electrical properties: comparison with perturbation theory
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
Investigation on the production of copper nitride (copper azide) thin films and their nanostructures
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
Annealing temperature effect on the mechanical and tribological properties of molybdenum nitride thin films
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