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.

Vertical diamond Schottky diodes with blocking voltages VBD > 2.4 kV and on-resistances R On < 400 mΩcm 2 were fabricated on homoepitaxially grown diamond layers with different surface morphologies. The morphology (smooth asgrown, hillock-rich, polished) influences the Schottky barrier, the carrier transport properties, and consequently the device performance. The smooth as-grown sample exhibited a low reverse current density JRev < 10 -4 A/cm 2 for reverse voltages up to 2.2 kV. The hillock-rich sample blocked similar voltages with a slight increase in the reverse current density (JRev < 10 -3 A/cm 2 ). The calculated 1D-breakdown field, however, was reduced by 30 %, indicating a field enhancement induced by the inhomogeneous surface. The polished sample demonstrated a similar breakdown voltage and reverse current density as the smooth as-grown sample, suggesting that a polished surface can be suitable for device fabrication. However, a statistical analysis of several diodes of each sample showed the importance of the substrate quality: A high density of defects both reduces the feasible device area and increases the reverse current density. In forward direction, the hillock-rich sample exhibited a secondary Schottky barrier, which could be fitted with a modified thermionic emission model employing the Lambert W-function. Both polished and smooth sample showed nearly ideal thermionic emission with ideality factors 1.08 and 1.03, respectively. Compared with literature, all three diodes exhibit an improved Baliga Figure of Merit for diamond Schottky diodes with VBD > 2 kV.

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