Zinc oxide films are used as a photovoltaic transparent electrodes for current collection. They are a good substitute for expensive transparent electrodes on the basis of Indium tin oxide. The ZnO films fabricated with a certain morphology of the structure are able to act as a light diffuser. When passing through a layer of this material solar radiation quantum changes its trajectory, so dispersion of radiation occurs, which leads to an increase in the optical path of the particle in the photoactive structure.
The study focuses on high-performance combined electro-spark alloying of titanium and titanium alloy (VT1-0, VT16) surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of biocompatible layered metal-oxide system Ti-Ta-(Ti,Ta)xOy. It was found that during electro-spark alloying the concentration of tantalum on the titanium surface ranges from 0.1 to 3.2 at.%. Morphology of the deposited splats is represented by uniformly grown crystals of titanium and tantalum oxides, which increase from nano- to submicron size.
Phononic crystals (PnC) with a specifically designed defect have been recently introduced as novel sensor platform. Those sensors feature a band gap covering the typical input span of the measurand as well as a narrow transmission peak within the band gap where the frequency of maximum transmission is governed by the measurand. This innovative approach has been applied for determination of compounds in liquids . Improvement of sensitivity requires higher probing frequencies around 100 MHz and above. In this range surface acoustic wave devices (SAW) provide a promising basis for PnC based microsensors . The respective feature size of the PnC SAW sensor has dimensions in the range of 100 μm and below. Whereas those dimensions are state of the art for common MEMS materials, etching of holes and cavities in piezoelectric materials having an aspect ratio diameter/depth is challenging. In this contribution we describe an improved technological process to manufacture considerably deep and uniform phononic crystal structures inside of SAW substrates.
The structure health monitoring becomes more and more important to increase the reliability of important assemblies and
structures. Therefore, a silicon test chip was developed to analyse acting mechanical loads at critical structure locations.
Standard MEMS technologies are used for manufacturing an array structure of stress sensitive elements. Up to 16
sections with each 6 stress sensitive resistors can be measured continuously by one measurement hardware unit. Interpretation and correction of the measured raw data is performed in proper computer software. The whole system can be utilized as a self-sufficient measurement chain for structure health monitoring.
This paper reports on a new method for estimation and minimization of mechanical stress on MEMS sensor and actuator structures due to packaging processes based on flip chip technology. For studying mechanical stress a test chip with silicon diaphragms was fabricated. A network of piezo-resistive solid state resistors created by diffusion was used to measure the surface tension pattern between adjacent diaphragms. Finite element method simulation was used to calculate the stress profile and to determine the optimum positions for placing the resistive network.