Aluminium nitride thin films directly grown on conducting boron-doped nanocrystalline diamond films without using buffer layer for high frequency applications

For the first time, AlN thin films directly grown on conducting B-NCD films without using buffer layer by reactive RF magnetron sputtering demonstrated. As we have not used chemical mechanical polished (CMP) diamond substrate or any buffer layer to grow AlN films on the diamond substrate, this simpler process will be very attractive for device fabrication. [Display omitted] •Aluminium Nitride films directly grown on conducting diamond films.•Diamond and Aluminium Nitride films interface was found void free and dense.•Aluminium Nitride films show better surface roughness properties. Aluminium Nitride (AlN)-diamond hetero-structures are promising candidates for high frequency acoustic wave resonator applications. This paper reports the electrical, piezoelectric and mechanical properties of AlN films directly grown on boron-doped nanocrystalline diamond (B-NCD) films. X-ray diffraction (XRD) and Raman spectroscopy were used to determine the crystallinity of B-NCD and AlN films. The resistivity (∼8 ×107Ω.m) and dielectric constant (∼14) were obtained from the electrical characterisation of the fabricated Al/AlN/B-NCD capacitors. Piezoelectric coefficient (d33, 4.3 pmV−1) of AlN films was measured by piezo force microscopy (PFM) technique. Nanoindentation technique was used to determine the hardness (∼14 GPa) and elastic modulus (∼202 GPa) of AlN films. These different properties of AlN/B-NCD/Si (100) hetero-structure show that it will provide a high-performance platform to realize high frequency resonators for 5G applications.