ABSTRACT
Sculptured thin lms (STFs) are lms prepared through glancing angle deposition techniques. In this technique the deposition system is combined with the rotor substrate through physical evaporation. Depending on the deposition rate, rotation speed of the substrate, and selection of the rotation axis, two STFs are created: helicoidal thin lms with bi-anisotropic media and sculptured nematic thin lms. Such lms are columnar thin lms (CTFs) whose columnar direction may be changed easily during deposition. They may be considered as a unilateral anisotropic heterogeneous continuum medium in visible, infrared, and low ultraviolet (UV) wavelengths. Porosity is the characteristic of these lms so that their anisotropy would be controlled through controlling porosity. Hence, such lms would be used in optics, nano-optics, and magneto-optics applications.1-10
Isolated masses ended in the substrate as parallel and chain-like matchwoods introduce columnar thin lms that were studied for the rst time in 1960 (selecting materials for the substrate and preparing such matchwoods are approximately innite). If these isolated and parallel arrangements of matchwoods, which redirect to the upward position of the substrate are deviated from the straight line and are twisted randomly, they introduce STFs. In electromagnetic waves with larger than columnar diameter wavelengths, CTFs and STFs are considered as homogenous anisotropic continuum media and unilateral anisotropic heterogeneous continuum media, respectively. Because STFs are porous, if they are penetrated by ¬uids or polymers, liquid crystals, nonorganic solids, and so forth, their constitutive features would be altered heterogeneously.11-19
STFs can be used in the following elds:
1. Optical sensors for biologic, chemical, or nuclear ¬uids 2. Linear and nonlinear optical circuits that may be combined with
electronic circuits 3. Nanocomposites with low permittivity and ultra-low permittivity
dams in multilm electronic chips 4. Biomedical parts such as microscreeners, viral traps, biocompatible
substrates, and fatty lms 5. Special catalytic reactors for asymmetric synthesis of mega-Dalton
polymers, chiral and antipest drugs
STFs are subdivided into two classes morphologically:
1. Thin lm helicoidal bianistropic media (TFHBM) 2. Sculptured nematic thin lms (SNTFs)
The difference between two STFs is determined through spatial changes of a unit vector, which is called a director. If a STF grows in the half space of z ≥ 0 and the substrate is in z = 0, the director will be a combination of the reference unit vector Ut (z) (z = 0) and a dyadic function S(z).
