Doped monolithic langasite structures for high temperature MEMS

Doping of langasite is performed in order to create monolithic structure components such as electrodes. In order to control the process, the diffusion coefficients of praseodymium, strontium and niobium are determined. An increase of the doping depth by application of an electric field is demonstrated. Strontium doped areas exhibit an increased conductivity by about 4 orders of magnitude. A langasite bulk acoustic wave resonator with Sr-doped areas as monolithic electrodes is operated up to 800 °C. For demonstration of the functionality and quality of langasite microstructures at elevated temperatures, planar and biconvex langasite membranes are prepared and characterized.