Vorlesungen anlaesslich der Mercator-Professur 1999.

The high degree of automation in industrial manufacturing and in many areas of the daily life requires as well as the continuous rising need for information of the society an technical measurement monitoring of various process and environmental parameters. Sensors convert the instantaneous value of a physical measured variable on basis of physical or chemical effects into an equivalent electrical signal. They build the interface between a technical system and its environment. Magnetic field sensors, like the sensor elements Hall-Element and magneto-resistor which are based on galvanomagnetic ef-fects, react to a magnetic interaction with the item under test or cause such an interac-tion. The starting point of the present study is built by the treatment of the components of galvanomagnetic sensor systems as shape elements out of defined material, which are used as information carrier by modification of the constructional parameters. The variation of number, arrangement and/or geometrical shape results in one- or multidi-mensionally structured system components, which allow the generation of defined sen-sor system topologies with custom-designed information content. Within the framework of this work different new sensor systems were developed, which open a broader appli-cation scope to the galvanomagnetic sensor technology by structured components and which permit the application of these sensors within purviews of the measuring tech-nique, which are dominated so far by sensors on basis of other, usually optical effects. If the allocation of a sensor signal to the structure of a system component is reproducible and biunique, then the principle of the structure variation also admits a purposeful cod-ing of defined discrete information. For this a beginning for the development of magnetic structure codes for the identification technology forms the conclusion of this thesis.

This work explains a method for optoelectronic integration of an heterojunction bipolar transistor (HBT) and a waveguide electroabsorption modulator (EAM). For this the epitactical layers of the individual devices based on III/V-semiconductors are merged into each other. The method has the advantage to reuse layers and results in a layer stack, which is easier to process technologically. Additionally to the manufacturing of the individual devices HBT and EAM, this integration enables a multifunctional device, which works in the optical and electronic regime simultaneously (HBT-EAM). This corresponds to an EAM with integrated amplifier. Presented are epitaxy, technological processing and measurement results.

In this thesis a circuit technology is described, which enables an integrated controling of an active matrix of micromechanic spatial light modulators (SLM). Possible applications areas for micromechanic spatial light modulators are projection of still or moving images, maskless lithography and adaptive optics. Especially in the areas of lithography and adaptive optics typical requirements of light modulators are high optical resolutions, high accuracy of modulation and fast addressing in order to enable a fast image repetition rate. The developed circuits are optimised for use as a maskless litography system and provide a minimum pixel pitch of 16 <font face="Symbol">m</font><i>m</i>. Demonstrators with image areas of 256 x 256 pixels and a modulation resolution of 16 steps on each pixel enabled a minimum geometric lithographic resolution of less than 20 nm, using today available optics.

The main point of this thesis is the validation of SA-ICP-MS for routine analysis in the steel industry. Therefor a new interface-system is build up in order to measure transient siganls from the continuos ablation process of the spark device. Further more the coupling of an ETV oven for slurry analysis and a Laser Ablation for isitope ratio determination is discriebed. Some fundamental aspects in formation of interference in ICP-MS are pointed out at the end of this thesis.

In the past, regional integration in Asia has basically been limited to market-driven economic integration and private networking. Policy-driven or institutional co-operation and integration have been very limited. The Asian financial crisis as well as the introduction of the Euro has contributed to a change in this pattern. A growing awareness of the advantages of regional co-operation is discernible among Asian states. The Chiang Mai initiative and numerous regional trade agreements are the most visible results of this growing awareness. Nevertheless it is to be doubted that this awareness will transform into concrete and higher level institutional integration among Asian states within the near future. The paper summarises the progress achieved so far in regional co-operation and integration and discusses the main factors favouring and limiting future perspectives.

In the present thesis the development of an analytical method for the determination of trace amounts of iron in dichlorosilane by graphite furnace atomic absorption spectrometry with a modified autoprobe unit is described. An conceived gas inlet system enabled a nearly contamination free and constant gas injection. The analytical method is optimized and the iron concentration in dichlorosilane is quantitatively determined.

In the field of radiological diagnostics, especially for the computed tomography a large number of photodetector elements (so called Pixels) is needed to assemble a large-area X-Ray-sensitive detector. These pixels should provide very high sensitivity, a very large dynamic range and a high signal-to-noise-ratio. Moreover, an in-pixel digitization of the signals is desired. To meet these specifications, a digital CMOS-Pixel comprising a special type of photodiode and a single-loop sigma-delta-modulator was developed, theoretically analyzed, fabricated and characterized. A matrix of 4x4 digital CMOS-pixels with each of them consuming an area of 1mm² has been fabricated. For further signal processing the concept of a multichannel decimation filter is presented.

This dissertation introduces an implantable LED microdisplay in the aim of returning a certain ability to see to blind people. The microdisplay is the basic device of the intraocular vision aid (IoVA) an implant developed for those whose cornea of the eye is considerably blurred due to accident or illness. This microdisplay consists of a LED-array which is connected to a CMOS driver circuit. By means of activating each pixel an image of the surroundings is generated and directly projected onto the retina. Within the scope of this dissertation the concepts and techniques of the intraocular vision aid are described. Physiological and technical parameters for application of the microdisplay are explained. That followed the material and applied technologies are defined. Finally the technological realization of the LED microdisplay is demonstrated as well as the first functional model on a worldwide scale.

We consider immersed hypersurfaces in euclidean $R^{n+1}$ which are stable with respect to an elliptic parametric functional with integrand $F=F(N)$ depending on normal directions only. We prove an integral curvature estimate provided that $F$ is sufficiently close to the area integrand, extending the classical curvature estimate of Schoen, Simon and Yau for stable minimal hypersurfaces in $R^{n+1}$. As a crucial point of our analysis we derive a generalized Simons inequality for the laplacian of the length of a weighted second fundamental form with respect to an abstract metric associated with $F$. Using Moser's iteration technique we finally prove a pointwise curvature estimate for $n leq 5$. As an application we obtain a new Bernstein result for complete stable hypersurfaces of dimension $n leq 5$.