Characteristics of single crystalline AlN films grown on Ru(0 0 0 1) substrates

We have grown AlN films on Ru(0 0 0 1) substrates using a low-temperature growth technique with pulsed laser deposition. We found that AlN(0 0 0 1) grows epitaxially on Ru(0 0 0 1) with an in-plane epitaxial relationship of AlN[112¯0]//Ru[112¯0]. Electron backscattering diffraction observations revealed that neither 30° rotational domains nor cubic phase domains were present in the AlN films and the full-width at half-maximum of the distribution in the AlN[0 0 0 1] crystalline orientation was 0.56°. Spectroscopic ellipsometry measurements showed that the AlN/Ru hetero-interface was quite abrupt, which is important for fabrication of high-frequency film bulk acoustic resonators.