•Mismatch strain-curvature relations for thin films on anisotropic substrate under large deformation.•Comparison of the analytical results with numerical simulations for Silicon wafer substrates.•The ...derived expressions for anisotropic substrates show improvement over existing results in the literature.
Thin film deposition is a key fabrication step in several opto-mechanical and electronics applications. For instance, thin film coatings can act as reflective interfaces, protective coatings or they can be used to modify the thermal behavior of the film-substrate system. For effective design, it is important to understand the deformation of the system in response to residual stresses during thin film deposition. The widely used Stoney’s equation to measure this deformation assumes isotropic elasticity of the substrate together with infinitesimal strains and rotations. In this work we relax both constraints, where we study the deformation of commonly used substrates made of single crystal Si(001) and Si(111) wafers that undergo large rotations. We derive relations between normalized substrate curvature and thin film mismatch strain and validate our analysis with numerical results. The methodology presented can be used for more accurate understanding of a broad range of film-substrate systems in semiconductors.
Liquid crystalline networks have been fashioned into thin films with tapered thicknesses, revealing the possibility of rolling up extremely tightly when triggered thermally or with light. Compared to ...the often limited bending shown previously in liquid crystal network actuators, these tapered films curl up several hundreds of degrees. Finite element results of simulated functionally graded thin films with tapered thicknesses corroborate well with experimental work.
Tight bending bio-inspired soft actuators were fashioned in liquid crystalline networks by using a novel tapered film geometry.
Global warming has been one of the major concerns of the century. The causes of this problem are the green-house gases. Due to the manmade mistakes the carbon dioxide (CO sub(2)) emission has reached ...highest of its level in recent years. Forest fires, haze and deforestation have contributed in increasing the CO sub(2) emissions to the atmosphere. Diagnosing these problems in the initial stage would definitely avert the major losses. This paper deals on detecting the changes in forest scenarios due to fire, felling of trees, etc. using a Geographical Information System (GIS) information analysis system using a pattern recognition concept, and detect the unusual changes and alert the system in early stage.
With recent developments in nanotechnology, self-assembled structures are providing convenient, cheaper and more precise ways of manufacturing various patterns and shapes with less complexity. Of ...these self-assembled structures, rolled-up nano-tubes play a vital role in various aspects. The notion is, the utilization of strain energy developed during epitaxial growth of a bilayer thin film over a substrate, mediated by a sacrificial layer. While the sacrificial layer is etched, the bilayer film is subjected to release its own in-built strain energy in the out-of-plane direction (3D structure) due to a bending stress induced by biaxial strain through the thickness, in the bilayer. This paper proposes a new method of fabricating conical self-rolled assembly by thickness and strain variations along the width of the bilayer and, cylindrical structure of variable radius due to thickness and strain variations along the length.
Residual stresses in a thin film deposited on a substrate results in a curvature of the system, which can be measured using the well known Stoney equation. Isotropic elasticity of the substrate along ...with infinitesimal strains and rotations are two important assumptions used in the derivation of the Stoney equation. However, the transverse deflection in the substrate contributes significantly to the extensional strain in its plane, leading to non-linearity in its deformation. Moreover, Silicon wafers are predominantly used as substrate materials to measure the curvature of the system. In this paper, relations between normalized substrate curvature and normalized thin film mismatch are derived in the non-linear deformation regime, for substrates made of single crystal Si(001) and Si(111) wafers. Numerical results of curvature of thin film configurations with Si(001) and Si(111) wafer substrates, undergoing large deformations are presented and discussed.
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