Oblique evaporation and surface diffusion

The special structure of obliquely evaporated films has its origin in shadowing phenomena during film growth. Because of shadowing, the film consists of bundles of inclined columns with the bundles being aligned perpendicularly to the vapour incidence direction. The column inclination angle lies between the film normal and the vapour incidence direction. Different models found in literature relating process parameters and film structure are discussed. It is found that surface diffusion plays an important role, especially with regard to the difference between random and directional surface diffusion. The latter is induced by the oblique evaporation process. A quantitative expression is given for the relation between process conditions and surface diffusion including the influence of substrate temperature, rate and contamination with residual gasses. Using these models and adding our new calculations, the relation between surface diffusion and film structure is discussed in detail and found to be consistent with measurements published in the literature

Laser Interference Lithography

In this chapter we explain how submicron gratings can be prepared by Laser Interference Lithography (LIL). In this maskless lithography technique, the standing wave pattern that exists at the intersection of two coherent laser beams is used to expose a photosensitive layer. We show how to build the basic setup, with special attention for the optical aspects. The pros and cons of different types of resist as well as the limitations and errors of the setup are discussed. The bottleneck in Laser Interference Lithography is the presence of internal reflection in the photo-resist layer. These reflections can be reduced by the use of antireflection coatings. However the thicknesses of these coatings depends on the angle of exposure and the material property or combination of materials in thin films. We show with some examples how to deal with this issue. Finally we show examples of more complex patterns that can be realized by multiple exposures

Design rationale for secure probe storage based on patterned magnetic media

We describe the design rationale for a hardware tamper resistant secure storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by magnetising individual dots perpendicular to the media plane. We report on an experiment to show that in principle the medium also supports a separate class of read/write-once operations by allowing individual dots in the media to be destroyed irreversibly by precise local heating. Security stems from the fact that bulk-erase is not possible

Self assembled three-dimensional nonvolatile memories

A promising strategy for for the realisation of three-dimensional memories could be the self assembly of articial sub-micron elements (smarticles). Such elements can be realised by combining edge-lithography techniques and anisotropic etching. The first experiments into this direction are encouraging

Agglomeration structure of superparamagnetic nanoparticles in a nematic liquid crystal medium:Image analysis datasets based on cryo-electron microscopy and polarised optical microscopy techniques

This dataset shows the agglomerate dimension and structure of oleic acid-coated superparamagnetic nanoparticles (SPIONs), which are dispersed in the nematic fluid of a thermotropic liquid crystal (LC), 4-cyano-4′-pentylbiphenyl (5CB). The analysed datasets were acquired from the raw images of the SPION-5CB mixtures obtained using cryogenic transmission electron microscopy (cryo-TEM) and polarised optical microscopy. The image data were quantitatively analysed to extract statistical information on the sizes of SPIONs and their agglomerates and the inter-particle spacing of the agglomerated SPIONs. This dataset supports the fundamental understanding on how colloidal nanospheres behave in an anisotropic fluid, and has a potential to be used as a part of database for automated design of new hybrid materials

Simulating three dimensional self-assembly of shape modified particles using magnetic dipolar forces

The feasibility of 3D self-assembly of milli-magnetic particles that interact via magnetic dipolar forces is investigated. Typically magnetic particles, such as isotropic spheres, self-organize in stable 2D configurations. By modifying the shape of the particles, 3D self-assembly may be enabled. The design of the particles and the experimental setup are presented. The magnetic configurations of simple particle arrangements are obtained via energy minimization in simulations. The simulations show that a 3D configuration can become energetically favourable over 2D configurations, if the shape of the particle is modified

High resolution MFM: Simulation of tip sharpening

The transfer functions of tips with various sharpened tip ends were calculated and the resolution of these tips was estimated by considering the resolution limit due to thermal noise at room temperature. The tip having an ellipsoidal tip end (ellipsoidal tip) is found to be a suitable candidate for high-resolution magnetic force microscopy. Sharpening of the flat tip end makes zero signal frequencies disappear for tips with ellipticities larger than tan45/spl deg/. The sensitivity shows a maximum around an ellipticity of tan80/spl deg/. The ellipsoidal tip shows a much smaller tip thickness dependence compared to the tip having a flat tip end because only the tip end mainly contributes to signals in case of the ellipsoidal tip