Macromolecular theory of solvation and structure in mixtures of colloids and polymers

The structural and thermodynamic properties of mixtures of colloidal spheres and non-adsorbing polymer chains are studied within a novel general two-component macromolecular liquid state approach applicable for all size asymmetry ratios. The dilute limits, when one of the components is at infinite dilution but the other concentrated, are presented and compared to field theory and models which replace polymer coils with spheres. Whereas the derived analytical results compare well, qualitatively and quantitatively, with mean-field scaling laws where available, important differences from ``effective sphere'' approaches are found for large polymer sizes or semi-dilute concentrations.Comment: 23 pages, 10 figure

Transient gels in colloid-polymer mixtures studied with fluorescence confocal scanning laser microscopy

We study the structure and the time evolution of transient gels formed in colloid-polymer mixtures, by means of uorescence Confocal Scanning Laser Microscopy (CSLM). This technique is used in conjunction with novel colloidal silica particles containing a uorescent core. The confocal micrographs reveal that there exist large differences in the local structure within a single system. At a given time there are regions where the gel structure consists of alternating patterns of colloid-rich and colloid-poor regions with a characteristic length scale and regions where the gel structure becomes disrupted by the formation of fractures. The number of fractures increases with time. It is speculated that the increase of the number of fractures leads to a weakening of the strength of the gel such that it eventually collapses under gravity

Comb capacitor structures for measurement of post-processed layers

We present a simple comb capacitive measurement structure to monitor the properties of post-processed layers. These measurement structures are easily fabricated in a single step in the last metallization layer of a standard IC process, while the post-processing layer in this article is formed over these comb structures by spray coating. The capacitive coupling of the structure on the substrate is modeled based on the electric field distribution around the structure. The change in composition of this post-processed layer is analyzed in terms of measured capacitance values

Comb Capacitor Structures for On-Chip Physical Uncloneable Function

Planar inter-digitated comb capacitor structures are an excellent tool for on-chip capacitance measurement and evaluation of properties of coating layers with varying composition. These comb structures are easily fabricated in a single step in the last metallization layer of a standard IC process. Capacitive coupling of these structures with a coating layer is modelled based on the electric field distribution to have a detailed understanding of contributing capacitance components. The coating composition is optimized to provide maximum spread in capacitance values of comb capacitor structures. This spread in measured capacitance values can be used to implement a physical uncloneable function (PUF). A PUF is a random function which can be evaluated only with the help of a physical system. We present an on-chip capacitive PUF for chip security and data storage in which the unlock key algorithm is generated from capacitors which are physically linked to the chip in an inseparable way. The strength of this key increases with the spread in capacitance values and measurement accuracy

Tin nitride thin films as negative electrode material for lithium-ion solid-state batteries

Tin nitride thin films have been reported as promising negative electrode materials for lithium-ion solid-state microbatteries. However, the reaction mechanism of this material has not been thoroughly investigated in the literature. To that purpose, a detailed electrochemical investigation of radio-frequency-sputtered tin nitride electrodes of two compositions (1:1 and 3:4) is presented for several layer thicknesses. The as-prepared thin films have been characterized by Rutherford backscattering spectrometry, inductively coupled plasma optical emission spectrometry, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The electrochemical results point out that the conversion mechanism of tin nitride most probably differs from the conversion mechanism usually observed for other oxide and nitride conversion electrode materials. The electrochemical data show that more than 6 Li per Sn atom can be reversibly exchanged by this material, whereas only about 4 are expected. Moreover, the electrochemical performance of the material is discussed, such as electrode cycle life, and a method for improving the cycle life is presented. Finally, thicker films have been characterized by Mössbauer spectroscopy. This technique opens a new route toward determining the conversion reaction mechanism of this promising electrode material. ©2010 The Electrochemical Societ