The AlN thin films were deposited on ultra-nano-crystalline diamond films (UNCD) using a buffer layer for the purpose of increasing the adhesion between the layers, enhancing the (002) texture characteristics of the films and improving the surface morphology of the AlN on UNCD films. The TiN/Ti double layer performs markedly superior on improving these characteristics of UNCD thin films to the TiN (or Ti) single layer does, which is ascribed to the additive performance of the two layers, viz. the Ti-layer improves the adhesion of the layers, whereas the TiN-layer minimizes the interaction of AlN with the underlying layer. The AlN/TiN/Ti/UNCD thin films with highly preferred-orientation (rocking curve < 4°∼5°), ultra flat and smooth surface (roughness < 15 nm ) and good piezoelectric properties (d33 ∼4.9 pm/V), which were good enough for device application, was obtained.
