Ion beam synthesis of iodide-selective membranes. (Ionenstrahlsynthese iodidsensitiver Membranen)

摘要

The continuous monitoring of the system und examination is of increasing importance in current analytical chemistry. This may be achieved by electrochemical sensors, both ion selective electrodes (ISE) and field effect structures being usable for data acquisition. Common to both systems is the sensitive membrane, silver iodide (AgI) being used in the present work. For membrane preparation, ion beam synthesis was chosen because of its compatibility to semiconductor technology. This method allows the fabrication of the miniaturized thin layer membrane. Ion-selective electrodes or capacitive sensors can be manufactured by suitable choice of substrate. The aim of ion beam synthesis on capacitive structures is primarily to set the stoichiometric relationship between silver and iodine. This can be well approximated by ion implantation through different overlayers, but can be achieved exactly with molecular ion implantation. The radiation damage generated in the substrate during the preparation process prevent the recording of evaluable measurement curves. This damage could not be completely eliminated with the methods available in the present work. In the preparation of sensitive membranes on silver, optimization of the preparation conditions made it possible to limit the sputtering losses which compete with implantation, and thus to achieve the formation of a membrane on a silver thin layer. The total amount of implanted ions and their distribution were determined with Rutherford backscattering spectroscopy (RBS). These membranes on silver substrates exhibit properties comparable to ion-selective electrodes, including nearly Nernstian sensitivity, high selectivity and good long-term stability. Furthermore, the sensitive thin-layer membranes can be miniaturized and integrated as microsensors in analytical microsystems. (orig.)