The effect of material anisotropy on the mechanics of a thin-film/substrate system under mechanical and thermal loads

In this study, the stress analysis for an orthotropic thin film bonded to an orthotropic elastic substrate is addressed using both the analytical and finite element methods. The analytical method employs the integrodifferential formulation with the aid of membrane assumption. Utilizing the finite element method, the effect of orientation of the material principal directions are studied. The loading scenarios include a temperature gradient imposed on the film and a far-field uniaxial tension on the substrate. The results of current study indicate that the ratio of the film to the substrate stiffness plays a leading role in the film stress distribution. For the mechanical loading applied to the substrate, a soft thin film attached to a relatively stiffer substrate is preferred. The film can tolerate the induced thermal stresses as it is bonded to a softer host structure. The rotation angle of material orthotropy directions significantly affects the stress singularity near the film edges up to a certain extent.

Surface Cleaning Challenges for Organic Light Emitting Diodes

Organic optoelectronic devices such as light-emitting diodes and solar cells present unique challenges for surface cleaning and preparation because of their large area and the ‘soft’, thin film nature of the materials involved. This paper gives an introduction to this class of semiconductor devices and covers a recent example of how surface cleaning impacts the long-term reliability of organic light-emitting diodes being commercialized for solid-state lighting.

Coherent Lorentz Imaging of Soft, Thin-Film Magnetic Materials

A detailed knowledge of the micromagnetic structure of thin films is essential for our understanding of the magnetic processes in modern magnetic materials. Many technological applications in the magnetic-recording industry involve thin-film materials including magnetic and magneto-optic recording media and magneto-resistive sensors. Electron microscopy allows imaging of the magnetic structure of such thin films with very high spatial resolution. It is also possible in certain instruments to study the behavior of the materials in the presence of a magnetic field while the specimen is still in the microscope. This facility offers the prospect of full magnetic characterization of thinned materials using electron microscopy.