Showing papers by "Wolfram Wersing published in 2006"

Shear mode FBARs as highly sensitive liquid biosensors

Abstract: Thin film bulk acoustic resonators (FBARs) operating in shear mode have been investigated for biosensing applications. Dynamic measurements in liquid were carried out and the adsorption of an antibody–antigen system was observed. Although this is the very first FBAR biosensor system operating in liquid environment it was found that the sensor performance ruled by the smallest detectable mass attachment, is already better (2.3 ng/cm 2 ) than that of QCMs. The ability of easy integration onto wafers together with readout-circuitry as well as the possibility of making up large arrays comprising pixels with different functionalities make these devices interesting for future acoustic biosensors.

c-axis inclined ZnO films for shear-wave transducers deposited by reactive sputtering using an additional blind

Abstract: This article reports on the growth and characterization of polycrystalline ZnO films having c axis inclined up to 16° with respect to the substrate normal. These films allow the excitation of shear and longitudinal waves with comparable electromechanical coupling constants and are of significant interest for thin film bulk acoustic resonators (FBARs). The films are deposited on silicon substrates covered by Al2O3 and SiO2 buffer layers under low pressure using a modified reactive dc-pulsed magnetron sputtering system. A blind has been positioned between target and substrate, allowing oblique particle incidence without tilting the wafer. The study of structural properties of the deposited ZnO films by x-ray diffraction and scanning electron microscopy has permitted to show the presence of the inclined structure. Electromechanical coupling constants K up to 13% have been extracted for shear-mode excitation using highly overmoded FBARs.

Thin-film condenser for detection of fluid e.g. liquid, has lower electrode layer with electrode layer ramps that are tilted opposite to substrate normal in same way around tilting angle, where ramps border directly at film

Abstract: The condenser has lower electrode layer (5), which is arranged on a substrate surface (31) of a substrate (3), where a substrate-normal is defined through the substrate surface. A zinc oxide film with a piezo ceramic material is arranged between the lower electrode layer and an upper electrode layer. The lower electrode layer has multiple electrode layer ramps at its side facing the film. The electrode layer ramps are tilted opposite to the substrate normal in a same way around a tilting angle. The electrode ramps border directly at the film. An independent claim is also included for a method for producing the thin-film condenser.