In this work, AlN and nanocrystalline diamond thin films as well as multi-layer structures on their basis are characterized towards their mechanical properties. In particular, the Young's modulus E and the residual stress s are obtained by wafer bow measurements of thin films as well as by bulge experiments and vibration measurements of freestanding membranes. Depending on the growth conditions, the AlN thin films, deposited by reactive magnetron sputtering, revealed values of s $ þ300 up to þ400 MPa and E $ 370 GPa, while the diamond films, grown by microwave plasma CVD, showed values of s $ À60 to þ60 MPa and E $ 870 up to 1000 GPa. The values and the accuracy of the characterization techniques used are discussed and their limits are demonstrated.

In this work we report on microstructures made of AlN for the use as piezoelectric microgenerators in energy harvesting applications. Experimental results on the mechanical and piezoelectrical properties of sputtered AlN thin films deposited on Si(001) substrates as well as results on vibrometry of fabricated microcantilevers are presented. It is shown that due to the constant d33 piezo coefficients of > 5 pm/V, AlN films are well suited for the integration in cantilever structures for powering of low-consumption sensor networks

In this work, the mechanical properties of thin piezoelectric AlN films along with the methods and instruments to obtain this information with sufficient accuracy via dynamic (vibration) and static analyses of thin membranes are reported. In addition, the impact of different damping mechanisms on the amplitude of forced oscillations have been considered in order to obtain the analytical expression relating the resonant amplitude of membrane to the ambient gas pressure

Inducing bistability with local electret technology in a microcantilever based non-linear vibration energy harvester

In this work, we show that thin biocompatible AlN films reveal a stable, frequency independent piezoresponse demonstrating a good applicability for implantable micro-generators. It was demonstrated that although more power is generated by resonant (tensile stressed) systems, e.g. cantilevers and planar membranes, the non-resonant (compressive stressed) systems, e.g. corrugated membranes, are preferable for this purpose due to the generation of sufficient power at low-frequency aperiodic vibrations and at very low accelerations

We present design and realization concepts for thin compound eye cameras with enhanced optical functionality. The systems are based on facets with individually tunable focus lengths and viewing angles for scanning of the object space. The active lens elements are made of aluminum nitride (AlN)/nanocrystalline diamond (NCD) membranes. This material system allows slow thermally actuated elements with a large deformation range as well as fast piezoelectric elements with a smaller deformation range. Due to the extreme mechanical stability of these materials, we are able to realize microoptical components with optimum surface qualities as well as an excellent long-term stability. We use facets of microlenses with 1 mm in diameter and a tunable focusing power to compensate for the focus shift for different viewing angles during the scanning procedure. The beam deflection for scanning is realized either by laterally shifting spherical elements or by a tunable microprism with reduced aberrations. For both actuators we present a design,fabrication concept and first experimental results

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